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Growth and characterization of an efficient semi organic single crystal: Sodium hydrogen oxalate monohydrate
Accepted Manuscript
Growth and characterization of an efficient semi organic single crystal: Sodium Hydrogen Oxalate Monohydrate C. Rathika Thaya Kumari , M. Nageshwari , S. Sudha , M. Lydia Caroline PII: DOI: Reference:
S0577-9073(18)30686-5 https://doi.org/10.1016/j.cjph.2018.09.038 CJPH 687
To appear in:
Chinese Journal of Physics
Received date: Revised date: Accepted date:
11 May 2018 3 September 2018 26 September 2018
Please cite this article as: C. Rathika Thaya Kumari , M. Nageshwari , S. Sudha , M. Lydia Caroline , Growth and characterization of an efficient semi organic single crystal: Sodium Hydrogen Oxalate Monohydrate, Chinese Journal of Physics (2018), doi: https://doi.org/10.1016/j.cjph.2018.09.038
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Highlights
The SHOM crystal discloses higher laser damage threshold value than KDP and Urea. SHOM possess negative nonlinearity. The dielectric properties proves its requirement in Opto-electronic applications and NLO devices. Microhardness study revealed that the crystal belongs to soft material category. The Z-scan signature for closed and open aperture were done to characterize the NLO response in SHOM.
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Growth and characterization of an efficient semi organic single crystal: Sodium Hydrogen Oxalate Monohydrate C. Rathika Thaya Kumaria, M. Nageshwaria, S. Sudhaa, M. Lydia Carolineb* Department of Physics, Arignar Anna Govt. Arts College, Cheyyar - 604 407, TamilNadu, India
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Department of Physics, Dr. Ambedkar Govt. Arts College, Vyasarpadi, Chennai - India
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Graphical abstract
Closed and Open aperture curve from Z- scan for SHOM crystal
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Abstract A highly proficient nonlinear optical compound Sodium Hydrogen Oxalate Monohydrate (SHOM) single crystal under semi organic category has been grown-up by the process of slow
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solvent evaporation. The triclinic structure and cell parameters of SHOM was revealed from X-ray diffraction analysis. The examination of FTIR was done to determine the existence of various functional groups present in the SHOM crystal. The mechanical stability is evaluated from Vicker’s microhardness tester and related mechanical parameters were assessed. The
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multiple shot laser damage threshold was examined to be 2.65 GW/cm2. TG/DTA analysis is carried out to appraise the thermal limit of the grown material. The absorbance spectrum was analyzed from UV-vis analysis which verifies high transparency of the grown crystal and various
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optical constants were also estimated. The third order nonlinearity, two-photon absorption and self-defocussing effect of the grown material was established from the Z-Scan approach. The
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results favoring the materials suitability over nonlinear optical applications are reported. Key words
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Crystal growth; nonlinear optical material; optical absorbance; Z-Scan.
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Corresponding author: Dr. M. Lydia Caroline, Fax: 044 - 2552 1852 Tel: +0091-04182-222286. +91 9841720216 E-mail:[email protected]
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1. Introduction In contemporary years, young researchers have dedicated their attention on emerging novel semi
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organic nonlinear optical materials. In diverse fields, semi organic materials have potent application because they merge the qualities of both organic and inorganic compounds. The properties of these materials show remarkable interest with low cut-off wavelength and stable physicochemical performances with high optical nonlinearities to realize many of the
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applications in laser technology, telecommunication, optical information processing etc. [1]. Recently, number of oxalate based metal structures [2] are reported because dicarboxylic acids and their metal complexes have remarkable applications in opto electronics based on their electrical conductivity and ferroelectricity [3-5]. Oxalic acid, a good crystalline, toxic organic
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dicarboxylic acid, having two carboxyl groups linked directly assures it as a strong organic acid with good nonlinear property. This can be easily oxidized with metals and form oxalates.
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Generally oxalates are a perfect reducing agents for photography, bleaching and removal of rust.
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The crystal structure of SHOM and its neutron diffraction study was reported already in the literature [6]. In the current research work, we report the growth and characterization of an
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efficient semi organic single crystal Sodium Hydrogen Oxalate Monohydrate (SHOM) for the first time. The diverse characterization studies assure it as an efficacious candidate in the field of
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nonlinear optics. The third order nonlinear susceptibility measurements were studied to prove the potentiality of SHOM in photonics and device fabrication. Moreover, optical, thermal and mechanical properties were analyzed and discussed elaborately. 2. Experimental Procedure 2.1 Material Synthesis
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An optically pure semi organic material SHOM was synthesized from a homogeneous solution of double distilled water containing oxalic acid and sodium hydroxide in a molar ratio 1:1. The reaction scheme for the synthesis of material is given below: +
NaOH
NaHC2O4. H2O
(A.1)
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C2H2O4
(Oxalic acid) (Sodium hydroxide)
(Sodium hydrogen oxalate monohydrate)
The synthesized salt was subjected to successive recrystallization process to enhance the purity
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of the material. 2.2 Seed Preparation
The recrystallized salt was dissolved in double distilled water by constant stirring at an ambient temperature. The optically transparent colorless seed crystal of SHOM was grown by slow
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evaporation method. The grown crystals were harvested after a span of 30 days.
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2.3 Crystal growth from slow evaporation method The good quality seed crystal was chosen and immersed into the prepared mother solution taken
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in a crystal growth vessel using nylon thread and allowed for slow evaporation to takes place in a
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dust free atmosphere. Finally, a well-defined optically hard transparent crystal with good morphology was grown by slow solvent evaporation technique. The structure and image of the
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grown SHOM are shown in Fig 1 & 2.
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. H2O
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Fig 1. Structure of SHOM crystal
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Fig 2. Image of SHOM crystal
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3. Results and Discussion
3.1 Analysis of single crystal XRD
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The X-ray diffraction analysis is carried out to identify the crystal system and cell parameters of the grown SHOM single crystal. This analysis is done with ENRAF NONIUS CAD 4 single crystal x-ray diffractometer with M0Kα radiation. The investigation reveals the triclinic crystal system with space group Pī. The cell parameters are found to be a = 5.74 Å, b = 6.53 Å, c = 6.74 Å and its interfacial angles are α = 74.99º, β = 84.73º, γ = 70.07º with volume V = 230 Å3 are in
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accordance with the already reported literature [6]. The computed XRD data of the present work and the reported work are represented in Table 1. Table 1. XRD data of SHOM related with reported literature [6] Crystal
Space
Cell Parameters
name
System
group
(Å)
SHOM
Triclinic
SHOM
Triclinic
Pī
Reported
3.2 FTIR Spectral Analysis
Pī
a= 6.50, b= 6.67, c= 5.69
(Å3)
V= 230
V= 224
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Work [6]
a= 6.53, b= 6.74, c= 5.74
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Work
Volume
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Present
Compound
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FTIR spectral examination, a key tool to identify the existing functional groups for the SHOM
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crystal, was performed by PERKIN ELMER Spectrophotometer in the range 4000 cm-1 – 400 cm-1. The observed spectrum is visualized in Fig. 3 which shows different vibrational modes of
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the grown single crystal. The position of O-H asserts the influence of the hydrogen atom [7]. In general, the OH bending is found to be around 3400 cm-1[8]. This assures the presence of
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monohydrate molecule in the grown crystal. The peak assigned at 3444 cm-1, 3415 cm-1 are due to strong and broad intermolecular O-H stretching. The symmetric stretching of C-H is positioned at 2889cm-1[9]. The peak appears at 1749 cm-1 and 1653 cm-1 are attributed to strong C=O stretching. The strong C-C stretching is observed at 1041 cm-1 [10]. The infrared band at 1615 cm-1 and 715 cm-1 are pertaining to the occurrence of C=C stretching in SHOM crystal. The
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C-OH in plane bending vibration corresponds to band positioned at 1347 cm-1 [7]. The band at 1424 cm-1 is assigned to the presence of O-H bending in dicarboxylic oxalic acid. The band attributed to 1251 cm-1 and 897 cm-1 are ascribed to the stretching vibration of C-O and C-C respectively. The vibrational assignments exactly specifies the occurrence of various functional
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groups in the as grown material.
Fig 3. FTIR Spectrum – Vibrational modes of SHOM crystal
3.3Vicker’s Microhardness Analysis The hardness of a material is a measure of resistance against lattice deformation or damage in the crystal [11]. The various mechanical parameters correlate with the crystal structure of the
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material. The material's hardness is estimated utilizing Vickers microhardness analysis. The hardness of the SHOM crystal was measured at room temperature using Leitz Wetzler microhardness tester fitted with the Vickers pyramidal indentor. The sample was subjected to indentations with load 25 gm, 50 gm and 100 gm with the indentation time for 10s. The Vicker’s
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microhardness number Hv was calculated using the formula [12], Hv = 1.8544 P/d2kgmm−2
(B.1)
where P and d indicates the applied load in kg and the indentation's average diagonal length in mm respectively. The plot between applied load P and its corresponding hardness number HV is
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illustrated in Fig. 4(a). Based on the bond strength of the material the graph shows linear or nonlinear behavior. The nonlinear behavior mainly corresponds to the cleavage plane of the crystal. The good elevation of hardness number with respect to load describes high mechanical
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strength of the material. The degree of hardness of the material is assured from the plot between log P with log d in Fig. 4(e). The relation connecting P and d is prescribed from the Meyer’s
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equation [12], P=adn
(B.2)
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n describes Meyer’s index or work hardening coefficient. The value of n declares whether the
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material corresponds to hard or soft category material. According to Onitsch, 1.0 < n < 1.6 for hard category material and n > 1.6 for soft category material. The slope of the straight line by
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least square fit imparts n value of the title compound as 3.82 clearly predicts that it belongs to soft category material [13]. The stiffness is a measure of the load increased to produce deformation in the material.
According to Wooster’s empirical formula, the stiffness constant (C11) for the grown crystal can be assigned utilizing [14],
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C11 = Hv 7/4
(B.3)
The plot between load P with Stiffness constant C11 is presented in Fig. 4(b) assures the dependence of stiffness constant with the sequentially applied load.
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Another mechanical parameter associated with hardness value is the Yield strength which is vital for device fabrication. The yield strength (σy) of the material can be formulated by the relation [12],
Hv (0.1) n2 3
(B.4)
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y
Where n’ = n+2.
Fig. 4(c) portrays the dependence of load P with Yield strength σ y. The Knoop hardness test is
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another microhardness test especially to identify the brittleness of the materials. The Knoop hardness number (Hk) is evaluated using the relation [12],
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P kg / mm 2 d2
(B.5)
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H k 14.229
Where P denotes the applied load in gm, d signifies the diagonal length in mm. The variation
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between load P and Knoop hardness number Hk is represented in Fig. 4(d).
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The fracture toughness Kc and brittleness index are elucidated employing the formula [12], Kc =
Bi =
⁄
(B.6)
(B.7)
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Here C denotes the crack length and β = 7 represents the indenter constant. The various mechanical parameters such as Hardness number, stiffness constant, Yield strength, Knoop hardness, Brittleness index for the grown SHOM are enumerated in the Table 2.
Load P (g)
HV
σy(GPa)
C11 (GPa)
(Kgmm-2)
HK
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Table 2. The calculated mechanical parameters for SHOM crystal n
Bi x 10^-5
3.82
2.947
3.82
3.473
(Kgmm-2)
22.45
2.315
7.483
17.231
50
32.05
4.317
10.683
24.676
100
43.9
7.487
14.633
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25
3.82
4.275
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3.3.1 Hays-Kendall (HK) approach
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The nonlinear performance of the material with various load can be analytically employed using
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Hays Kendall approach [12]. The information about the Indentation Size Effect behavior of
(C.1)
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P = W + A1dn
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materials and the load dependence of hardness may be expressed by
where W indicates the minimum load to initiate plastic permanent deformation and A1 is a load-
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independent constant with the exponent of n = 3.82. W and A1 have been evaluated from the plot against load P and d2 is shown in Fig. 4(f). The negative resistance pressure from the graph declares the strong Reverse Indentation Size Effect (RISE) behavior of the crystal corresponds to the applied load. The corrected load independent hardness HHK can be calculated utilizing the relation,
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(C.2)
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HHK = 1854.4A1
Fig. 4(a) Hardness number (HV)
(b) Stiffness Constant (C11) (c) Yield strength (σy)
(d) Knoop Hardness number (e) Log d vs Log P
(f) d2 Vs load P
Moreover, the calculated resistance pressure (W) and load independent constant (A1) values are specified in Table 3.
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Table 3. Estimated Hay’s Kendall constant W, A1 and HHK for SHOM Results
Resistance pressure (W)
- 47.11 (g)
Load independent constant (A1)
0.0343 (g/μm2)
Corrected load independent hardness (HHK)
63.61 (g/μm2)
3.4 Laser Damage Threshold
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HK constant
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The LDT analysis is very essential for NLO crystals because when a high power laser is irradiated to the surface of the crystal it should withstand or it may limit its performance in NLO applications. This can be measured by single or multiple shot, mostly multiple shot mode is more
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preferable so that NLO crystals are notable for long duration repetitive mode for different optical applications.
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The grown SHOM crystal was polished and mounted on the crystal holder. A high power
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Nd:YAG laser beam was allowed to fall on the crystal surface. The energy of the laser beam was increased from 5 mJ for a time duration of 10 ns for all measurements to take place. The spot
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size of the beam was adjusted to be 1 mm and the observations are noted. As the energy increases, a small dot like mark was spotted on the crystal surface and was observed by an
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optical microscope. To view more clearly, same laser beam with high repetitive rate was irradiated at different spots on the same crystal at similar condition. The surface damage profile was observed clearly by an optical microscope. The surface damage threshold of the crystal was calculated using the formula [15], Power density Pd = E / τ A
(D.1)
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where E(mJ), τ(ns) and r(mm) represents energy, pulse width and radius of the spot respectively. The calculated surface damage was appraised to be 2.65 GW/cm2 which exhibits higher value compared to KDP (0.20 GW/cm2) and urea (1.50 GW/cm2) [16]. The NLO material with low laser damage threshold will rigorously limit the optical applications. Hence the grown material
radiation. 3.5 Thermal and Differential Thermal Analysis
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SHOM with high laser damage threshold value possess an excellent resistant to high power laser
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The thermal and differential thermal analysis were studied to understand about the melting point, decomposition, phase analysis and stability of the grown SHOM crystal. The powder sample was employed to thermal analyzer technique to assess the weight loss (TG) and change in energy (DTA) for the corresponding temperature. The TG-DTA study was examined
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using SII-NANO TECHNOLOGY (MODELTG/DTA6200) in the temperature range 50- 600˚C
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at a heating rate of 20˚C min-1 in an alumina crucible in a nitrogen atmosphere. The TG/DTA curve for the as grown semi organic crystal is depicted in Fig. 5. The examined curve assures a
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sharp endothermic peak at 134.7 0C which coincides with the melting point of the compound. Further two more endothermic transition occurs at 267.6 0C represents 43.2 % and 557.8 0C at
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12% weight loss respectively. The TGA curve illustrates the complete decomposition of the
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sample. The decomposition occurs in steps could be due to the decomposition and volatilization of the title compound [17]. Thus the results of TG-DTA, conveys the thermal stability and shows a vital applicant in nonlinear optical applications.
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Fig. 5 TG/DTA Curve for SHOM crystal
3.5 Linear and Nonlinear Optical Analysis
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3.5.1 Optical Absorbance Analysis
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The spectral examination of an UV – Visible spectrum of the grown SHOM crystal was carried out using LAMBDA-35 UV-Vis spectrophotometer in the range of 100 nm -1200 nm. The knowledge about band structure and impurity levels in solids are much essential to enhance the optical transparency of the grown crystal. The observed UV – Visible spectrum of SHOM is shown in Fig. 6(a).Generally, the higher absorption indicates the presence of flaws or impurities in the crystal. In SHOM, the lower cut off wavelength observed at 225 nm exhibits intense
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transparency in the entire visible region substantiates the materials effectiveness in the application for optoelectronics facilitating its suitability in the sector of nonlinear optics. The optical absorption coefficient (α) can be determined from the transmittance spectrum
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utilizing the relation [18], 2.3026 log(1 / T ) t
(E.1)
where, T is the transmittance (%), and t be the thickness of the sample (cm). A Tauc’s plot of
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(αhυ)2 verses Photon energy (hυ) in eV is shown in Fig. 6(b) has been plotted to elucidate the band gap energy value. The optical band gap energy Eg shows the intersection of the extrapolated line with the photon energy axis and was found to be 5.37 eV. As a consequence of this wide band gap, the grown crystal has a large transmittance in the visible region confirms the decrease
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of defect concentration [19]. The estimated large optical band gap suggests that the crystal
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acquire dielectric nature to stimulate polarization when intense radiation falls on it [20].
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Fig. 6(a) & 6(b) UV- Visible spectrum & Tauc’s plot – Band gap of SHOM crystal 3.5.2 Determination of Optical Parameters
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The various optical parameters are very essential to understand the materials potential towards
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nonlinear applications. The reflectance, extinction coefficient, refractive index, susceptibility measurements are carried out from absorption coefficient (α) gains knowledge to understand about the materials atomic structure, electronic band structure and electrical properties. The variation of Reflectance (R), Extinction coefficient (K) and Refractive index (n) shows a significant interactions between photon and electron.
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The extinction coefficient (K) and reflectance (R) associated to the absorption coefficient (α)is utilized from the relation [18],
4
(F.1)
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K
√
(F.2)
Fig. 7(a),(b) illustrates the variation of reflectance R, extinction coefficient K with respect to
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photon energy hν. The low reflectance and extinction coefficient predicts higher transmittance of
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the grown crystal shows remarkable applications in nonlinear optics.
Fig. 7(a) Photon energy hν verses Reflectance R and (b) Extinction coefficient (K)
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The Refractive index (n) can be evaluated directly from reflectance R, employing the relation [19]: 2 ( R 1) 3R *10 R 3 n 2( R 1)
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(F.3)
The interaction of light with matter is understand from the refractive index dispersion of the material. Fig. 8(a) portrays the change of refractive index n with the photon energy. The refractive index gradually decreases with photon energy. The refractive index of grown crystal
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was attained to be 1.589 in the transmission range. The optical parameters refractive index, reflectance and extinction coefficient reveals that the grown crystal is more transparent to transmit the light from 220 nm to 1100 nm. Hence the optical constants undoubtedly supportive
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to study the material’s suitability in the application of opto electronic devices [21].
n K 2 0 c 0 4
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2
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The electric susceptibility (χc) can be formulated using the relation [19],
(F.4)
Fig. 8(b) shows the variation of electric susceptibility with photon energy. Since the electrical
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susceptibility is greater than 1, the material can be easily polarized due to powerful intense
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incident light assures SHOM as an efficient nonlinear optical material [22].
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Fig. 8(a) & (b) Photon energy verses Refractive index & Electric Susceptibility 3.5.3 Z- Scan Analysis
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Z- Scan technique is a simple and accurate method to determine the nonlinear absorption and
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refractive index of crystals, thin films and liquid solutions by Shakebahae [23]. This is a standard single beam method for measuring the sign and magnitude of nonlinear absorption (β) and nonlinear refractive index (n2) and nonlinear susceptibility (χ3) which has widely accepted by nonlinear optics community due to a simplicity of interpretation. Materials with large nonlinearities are commonly focused on high speed optical switching devices [24].
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The third order nonlinear properties of the grown crystal can be measured using He – Ne laser (5mW, 632.8 nm) as a source with a beam diameter of 0.5 mm. The single Gaussian beam was directed through a convex lens with a focal length of 30 mm and the focal point is taken as Z = 0 [25]. The variation in far field transmittance beam intensity was measured through the closed
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aperture using a digital power meter. The nonlinear absorption and nonlinear refractive index directly affects the amplitude and phase of the applied field and can be measured by closed and open aperture method using Z Scan technique.
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From the results of Z-scan, the difference between the normalized valley and peak transmittance ΔTp-v can be determined by [24], | |
(G.1)
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where| | represents the on – axis phase shift at the focus. S is the linear transmittance aperture and is estimated by )
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⁄
(G.2)
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Here ra is the radius of the aperture and ωa be the beam radius at the aperture.
| |
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The on – axis phase shift | | is given by [24], (G.3)
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Where Leff = (1-e-αL) / α
Here L denotes the sample length, α represents the linear absorption coefficient, I0 be the laser beam intensity at focus Z=0 and k represents the wave number (k= 2π / λ).
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From the open aperture trace, the nonlinear absorption coefficient can be determined using the relation [24], √
(G.4)
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is the one valley value at the open aperture normalized transmittance Z-scan trace.
ZR = (K ω02 / 2) which determines the beam diffraction length, ω0 represents the waist radius of the beam. The value of nonlinear absorption coefficient β will be positive for two photon
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absorption and negative for saturation absorption. The real and imaginary part of nonlinear optical susceptibility is carried out using the experimentally determined value of n2 and β which
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is given by [24],
(G.6)
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)
(G.5)
Where ε0 and C represents the permittivity of free space in vacuum and the velocity of light in
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refractive index.
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vacuum respectively. The real part of susceptibility completely depends on the nonlinear
The absolute third order nonlinear optical susceptibility was estimated using the relation [24], |
(
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)
(
)
⁄
(G.7)
The negative nonlinearity of the sample shows transmittance peak followed by valley, similarly the positive nonlinearity shows the transmittance valley followed by peak. Fig. 9 illustrates the closed aperture profile for SHOM crystal shows peak followed by valley confirms negative nonlinear refractive index i.e. the presence of self – defocusing of the grown crystal. Fig. 10
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indicates the open aperture curve for SHOM crystal. The positive value of β clearly indicates the process of two photon absorption and is widely employed for optical power limiting applications [26]. Fig. 11 shows the Z- scan ratio of the SHOM crystal. Table 4 indicates the experimental results of the Z-scan technique for SHOM crystal. Eventually, the nonlinear absorption and
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nonlinear refraction is related to two photon absorption process and self-defocusing nature of SHOM respectively. Due to excellent nonlinear response it is concluded that it could be a potent candidate for NLO device fabrication.
Third order nonlinear properties
Measured values 5.99 x 10-8 cm2/W
Nonlinear refractive index (n2)
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Nonlinear absorption coefficient (β) Real susceptibility (χR (3)) Imaginary susceptibility (χI (3))
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Absolute susceptibility (χ3)
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Table 4: Third order nonlinear optical parameters from Z – scan for SHOM crystal
0.08 x 10-4 cm/W
8.458 x 10-6esu 0.494 x 10-6esu 8.472 x 10-6 esu
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Fig. 9 Closed aperture curve for SHOM crystal
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Fig. 10 Open aperture curve for SHOM crystal
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4. Conclusion
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Fig. 11 Z - Scan ratio of SHOM crystal
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Our investigation on good optical transparent semi organic Sodium Hydrogen Oxalate
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Monohydrate (SHOM) single crystal have been synthesized effectively and harvested successfully from the mother solution by slow solvent evaporation method. The single crystal XRD study declares the triclinic crystal system with a space group of Pī confirms the centrosymmetric nature of the grown material. The cell parameters were also analyzed and compared with the reported literature. The diverse vibrational assignments of SHOM were concluded applying FTIR instrumentation. Vickers microhardness analysis indicates the
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existence of reverse indentation size effect in the crystal thereby exhibiting the soft nature. The LDT experiment shown that the grown crystal possess an excellent resistant to high power laser radiation with a high threshold upto 2.65 GW/cm2 exhibit better compared with other organic and semi organic materials. The thermal stability and decomposition of SHOM are examined by
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TG/DTA analyses. Several optical parameters specifically transmittance, energy gap, reflectance, extinction coefficient, have been assessed by UV–Vis spectral study. Z-scan studies showed that the SHOM crystal possess self-defocusing nature with nonlinear absorption coefficient and nonlinear refractive index. The detailed characterization and optical nonlinearity attest its
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suitability and reliability in optoelectronics, photonics and optical limiting devices. Acknowledgement
The scientific supports rendered by sophisticated analytical instrument facility IITM, for support
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in single crystal XRD and FTIR is gratefully acknowledged. The facilities rendered by Department of Polymer and Nanoscience of BS Abdul Rahman University (BSAU), Chennai for
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providing thermal analysis measurement is gratefully thanked. The authors give their sincere
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References
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thanks to St.Joseph’s College Trichy for providing the microhardness analysis.
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[10] C. Ramachandra Raja, A. Antony Joseph, Crystal growth and comparative studies of XRD, spectral studies on new NLO crystals: L-Valine and L-Valinium succinate, Spectrochim. Acta A, 74 (2009) 825-828.
indentation hardness testing, J. Dairy sci. 41 (1958) 360-368.
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[11] B.W. Mott, Hardness of Butter, Influence of season and manufacturing method micro
[12] M. Nageshwari, C. Rathika Thaya Kumari, P. Sangeetha, G. Vinitha, M. Lydia Caroline, Third order nonlinear optical, spectral, dielectric, laser damagethreshold, and photo
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luminescence characteristics of an efficacious semiorganic acentric crystal: L-Ornithine monohydrochloride, Chinese Journal of Physics, 56 (2018) 502–519.
[13] E.M. Onitsch, The present status of testing the hardness of materials, Mikroskopie 95 (1956) 12-14.
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[14] W.A. Wooster, Physical properties and atomic arrangement in crystals, Rep. Prog. Phys. 16
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(1953) 62-82.
[15] P. Vivek, A. Suvitha, P. Murugakoothan, Growth, spectral, anisotropic, second and third
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order nonlinear optical crystal anilinium perchlorate (AP) for NLO device fabrications,
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Spectrochimica Acta A: Molecular and Biomolecular Spectroscopy 134 (2015) 517-525. [16] N.Vijayan, G.Bhagavannarayana, K.R.Ramesh, R.GopalaKrisnan, K.K.Maurya and
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P.Ramasamy, A comparative study on solution- and Bridgman – grown single crystals of Benzimidazole by High resolution x-ray diffractometry, Fourier Transform Infrared , Microhardness, Laser Damage Threshold , and Second harmonic generation measurement , Cryst. Growth Des.2006, 6, 1542- 1546.
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[17] P. Jayaprakash, M. Peer Mohamed, P. Krishnan, M. Nageshwari, G. Mani, M. Lydia Caroline, Growth, spectral, thermal, laser damage threshold, microhardness, dielectric, linear and nonlinear optical properties of an organic single crystal: L-phenylalanine DL-mandelic acid, Physica B, 503 (2016) 25-31.
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[18] C. Rathika Thaya Kumari, P. Jayaprakash, M. Nageshwari, M. Peer Mohamed, P. Sangeetha and M. Lydia Caroline, Growth, optical, photoluminescence, dielectric, second and third order nonlinear optical studies of benzoyl valine acentric crystal, Molecular Crystals and Liquid
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Crystals, 658 (2017) 186 – 197.
[19] M. Nageshwari, P. Jayaprakash, C. Rathika Thaya Kumari, G. Vinitha, M. Lydia Caroline, Growth, spectral, linear and nonlinear optical characteristics of an efficient semiorganic acentric crystal: L-Valinium L-Valine chloride. Physics B. 511 (2017) 1-9. Sagadevan
Suresh, The
growth and
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[20]
the optical,
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Photoconductivity properties of a new nonlinear optical crystal- L-Phenylalanine-4 nitrophenol NLO single crystal, Journal of crystallization process and Technology, 3 (2013) 87-91.
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[21] V. Sangeetha, K. Gayathri, P. Krishnan, N. Sivakumar, N. Kanagathara, G. Anbalagan,
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Growth, optical, thermal, dielectric and microhardness characterizations of melaminium bis (trifluoroacetate) trihydrate single crystal, J. Crys. Growth 389 (2014) 30-38.
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[22] Sagadevan Suresh, Synthesis, growth and characterization of L-threonine zinc acetate (LTZA) NLO single crystal, Optik, 125 (2014) 4547-4551. [23] M. Sheik-Bahae, A. A. Said, T. H. Wei, D. J. Hagan, and E. W. VanStryland, Sensitive measurement of optical nonlinearities using a single beam, IEEE Journal of Quantum electronics, 26 (1990) 760 –769.
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[24] C. Rathika Thaya Kumari, M. Nageshwari, R. Ganapathi Raman, M. Lydia Caroline, Crystal growth, spectroscopic, DFT computational and third harmonic generation studies of nicotinic acid, Journal of Mol. Struct. 1163 (2018) 137-146. [25] C. Balarew and R. Duhlew, Application of the hard and soft acids and bases concept to
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[26] P. Nagapandiselvi, C. Baby, R. Gopala Krishnan, Synthesis, growth, structure and nonlinear optical properties of a semi organic 2-carboxy pyridinium dihydrogen phosphate single crystal,
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Optical materials 47, (2015) 398-405.
Growth and characterization of an efficient semi organic single crystal: Sodium Hydrogen Oxalate Monohydrate C. Rathika Thaya Kumari , M. Nageshwari , S. Sudha , M. Lydia Caroline PII: DOI: Reference:
S0577-9073(18)30686-5 https://doi.org/10.1016/j.cjph.2018.09.038 CJPH 687
To appear in:
Chinese Journal of Physics
Received date: Revised date: Accepted date:
11 May 2018 3 September 2018 26 September 2018
Please cite this article as: C. Rathika Thaya Kumari , M. Nageshwari , S. Sudha , M. Lydia Caroline , Growth and characterization of an efficient semi organic single crystal: Sodium Hydrogen Oxalate Monohydrate, Chinese Journal of Physics (2018), doi: https://doi.org/10.1016/j.cjph.2018.09.038
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Highlights
The SHOM crystal discloses higher laser damage threshold value than KDP and Urea. SHOM possess negative nonlinearity. The dielectric properties proves its requirement in Opto-electronic applications and NLO devices. Microhardness study revealed that the crystal belongs to soft material category. The Z-scan signature for closed and open aperture were done to characterize the NLO response in SHOM.
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Growth and characterization of an efficient semi organic single crystal: Sodium Hydrogen Oxalate Monohydrate C. Rathika Thaya Kumaria, M. Nageshwaria, S. Sudhaa, M. Lydia Carolineb* Department of Physics, Arignar Anna Govt. Arts College, Cheyyar - 604 407, TamilNadu, India
b
Department of Physics, Dr. Ambedkar Govt. Arts College, Vyasarpadi, Chennai - India
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Graphical abstract
Closed and Open aperture curve from Z- scan for SHOM crystal
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Abstract A highly proficient nonlinear optical compound Sodium Hydrogen Oxalate Monohydrate (SHOM) single crystal under semi organic category has been grown-up by the process of slow
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solvent evaporation. The triclinic structure and cell parameters of SHOM was revealed from X-ray diffraction analysis. The examination of FTIR was done to determine the existence of various functional groups present in the SHOM crystal. The mechanical stability is evaluated from Vicker’s microhardness tester and related mechanical parameters were assessed. The
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multiple shot laser damage threshold was examined to be 2.65 GW/cm2. TG/DTA analysis is carried out to appraise the thermal limit of the grown material. The absorbance spectrum was analyzed from UV-vis analysis which verifies high transparency of the grown crystal and various
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optical constants were also estimated. The third order nonlinearity, two-photon absorption and self-defocussing effect of the grown material was established from the Z-Scan approach. The
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results favoring the materials suitability over nonlinear optical applications are reported. Key words
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Crystal growth; nonlinear optical material; optical absorbance; Z-Scan.
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Corresponding author: Dr. M. Lydia Caroline, Fax: 044 - 2552 1852 Tel: +0091-04182-222286. +91 9841720216 E-mail:[email protected]
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1. Introduction In contemporary years, young researchers have dedicated their attention on emerging novel semi
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organic nonlinear optical materials. In diverse fields, semi organic materials have potent application because they merge the qualities of both organic and inorganic compounds. The properties of these materials show remarkable interest with low cut-off wavelength and stable physicochemical performances with high optical nonlinearities to realize many of the
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applications in laser technology, telecommunication, optical information processing etc. [1]. Recently, number of oxalate based metal structures [2] are reported because dicarboxylic acids and their metal complexes have remarkable applications in opto electronics based on their electrical conductivity and ferroelectricity [3-5]. Oxalic acid, a good crystalline, toxic organic
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dicarboxylic acid, having two carboxyl groups linked directly assures it as a strong organic acid with good nonlinear property. This can be easily oxidized with metals and form oxalates.
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Generally oxalates are a perfect reducing agents for photography, bleaching and removal of rust.
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The crystal structure of SHOM and its neutron diffraction study was reported already in the literature [6]. In the current research work, we report the growth and characterization of an
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efficient semi organic single crystal Sodium Hydrogen Oxalate Monohydrate (SHOM) for the first time. The diverse characterization studies assure it as an efficacious candidate in the field of
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nonlinear optics. The third order nonlinear susceptibility measurements were studied to prove the potentiality of SHOM in photonics and device fabrication. Moreover, optical, thermal and mechanical properties were analyzed and discussed elaborately. 2. Experimental Procedure 2.1 Material Synthesis
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An optically pure semi organic material SHOM was synthesized from a homogeneous solution of double distilled water containing oxalic acid and sodium hydroxide in a molar ratio 1:1. The reaction scheme for the synthesis of material is given below: +
NaOH
NaHC2O4. H2O
(A.1)
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C2H2O4
(Oxalic acid) (Sodium hydroxide)
(Sodium hydrogen oxalate monohydrate)
The synthesized salt was subjected to successive recrystallization process to enhance the purity
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of the material. 2.2 Seed Preparation
The recrystallized salt was dissolved in double distilled water by constant stirring at an ambient temperature. The optically transparent colorless seed crystal of SHOM was grown by slow
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evaporation method. The grown crystals were harvested after a span of 30 days.
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2.3 Crystal growth from slow evaporation method The good quality seed crystal was chosen and immersed into the prepared mother solution taken
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in a crystal growth vessel using nylon thread and allowed for slow evaporation to takes place in a
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dust free atmosphere. Finally, a well-defined optically hard transparent crystal with good morphology was grown by slow solvent evaporation technique. The structure and image of the
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grown SHOM are shown in Fig 1 & 2.
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-
. H2O
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Fig 1. Structure of SHOM crystal
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Fig 2. Image of SHOM crystal
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3. Results and Discussion
3.1 Analysis of single crystal XRD
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The X-ray diffraction analysis is carried out to identify the crystal system and cell parameters of the grown SHOM single crystal. This analysis is done with ENRAF NONIUS CAD 4 single crystal x-ray diffractometer with M0Kα radiation. The investigation reveals the triclinic crystal system with space group Pī. The cell parameters are found to be a = 5.74 Å, b = 6.53 Å, c = 6.74 Å and its interfacial angles are α = 74.99º, β = 84.73º, γ = 70.07º with volume V = 230 Å3 are in
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accordance with the already reported literature [6]. The computed XRD data of the present work and the reported work are represented in Table 1. Table 1. XRD data of SHOM related with reported literature [6] Crystal
Space
Cell Parameters
name
System
group
(Å)
SHOM
Triclinic
SHOM
Triclinic
Pī
Reported
3.2 FTIR Spectral Analysis
Pī
a= 6.50, b= 6.67, c= 5.69
(Å3)
V= 230
V= 224
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Work [6]
a= 6.53, b= 6.74, c= 5.74
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Work
Volume
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Present
Compound
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FTIR spectral examination, a key tool to identify the existing functional groups for the SHOM
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crystal, was performed by PERKIN ELMER Spectrophotometer in the range 4000 cm-1 – 400 cm-1. The observed spectrum is visualized in Fig. 3 which shows different vibrational modes of
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the grown single crystal. The position of O-H asserts the influence of the hydrogen atom [7]. In general, the OH bending is found to be around 3400 cm-1[8]. This assures the presence of
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monohydrate molecule in the grown crystal. The peak assigned at 3444 cm-1, 3415 cm-1 are due to strong and broad intermolecular O-H stretching. The symmetric stretching of C-H is positioned at 2889cm-1[9]. The peak appears at 1749 cm-1 and 1653 cm-1 are attributed to strong C=O stretching. The strong C-C stretching is observed at 1041 cm-1 [10]. The infrared band at 1615 cm-1 and 715 cm-1 are pertaining to the occurrence of C=C stretching in SHOM crystal. The
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C-OH in plane bending vibration corresponds to band positioned at 1347 cm-1 [7]. The band at 1424 cm-1 is assigned to the presence of O-H bending in dicarboxylic oxalic acid. The band attributed to 1251 cm-1 and 897 cm-1 are ascribed to the stretching vibration of C-O and C-C respectively. The vibrational assignments exactly specifies the occurrence of various functional
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groups in the as grown material.
Fig 3. FTIR Spectrum – Vibrational modes of SHOM crystal
3.3Vicker’s Microhardness Analysis The hardness of a material is a measure of resistance against lattice deformation or damage in the crystal [11]. The various mechanical parameters correlate with the crystal structure of the
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material. The material's hardness is estimated utilizing Vickers microhardness analysis. The hardness of the SHOM crystal was measured at room temperature using Leitz Wetzler microhardness tester fitted with the Vickers pyramidal indentor. The sample was subjected to indentations with load 25 gm, 50 gm and 100 gm with the indentation time for 10s. The Vicker’s
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microhardness number Hv was calculated using the formula [12], Hv = 1.8544 P/d2kgmm−2
(B.1)
where P and d indicates the applied load in kg and the indentation's average diagonal length in mm respectively. The plot between applied load P and its corresponding hardness number HV is
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illustrated in Fig. 4(a). Based on the bond strength of the material the graph shows linear or nonlinear behavior. The nonlinear behavior mainly corresponds to the cleavage plane of the crystal. The good elevation of hardness number with respect to load describes high mechanical
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strength of the material. The degree of hardness of the material is assured from the plot between log P with log d in Fig. 4(e). The relation connecting P and d is prescribed from the Meyer’s
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equation [12], P=adn
(B.2)
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n describes Meyer’s index or work hardening coefficient. The value of n declares whether the
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material corresponds to hard or soft category material. According to Onitsch, 1.0 < n < 1.6 for hard category material and n > 1.6 for soft category material. The slope of the straight line by
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least square fit imparts n value of the title compound as 3.82 clearly predicts that it belongs to soft category material [13]. The stiffness is a measure of the load increased to produce deformation in the material.
According to Wooster’s empirical formula, the stiffness constant (C11) for the grown crystal can be assigned utilizing [14],
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C11 = Hv 7/4
(B.3)
The plot between load P with Stiffness constant C11 is presented in Fig. 4(b) assures the dependence of stiffness constant with the sequentially applied load.
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Another mechanical parameter associated with hardness value is the Yield strength which is vital for device fabrication. The yield strength (σy) of the material can be formulated by the relation [12],
Hv (0.1) n2 3
(B.4)
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y
Where n’ = n+2.
Fig. 4(c) portrays the dependence of load P with Yield strength σ y. The Knoop hardness test is
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another microhardness test especially to identify the brittleness of the materials. The Knoop hardness number (Hk) is evaluated using the relation [12],
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P kg / mm 2 d2
(B.5)
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H k 14.229
Where P denotes the applied load in gm, d signifies the diagonal length in mm. The variation
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between load P and Knoop hardness number Hk is represented in Fig. 4(d).
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The fracture toughness Kc and brittleness index are elucidated employing the formula [12], Kc =
Bi =
⁄
(B.6)
(B.7)
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Here C denotes the crack length and β = 7 represents the indenter constant. The various mechanical parameters such as Hardness number, stiffness constant, Yield strength, Knoop hardness, Brittleness index for the grown SHOM are enumerated in the Table 2.
Load P (g)
HV
σy(GPa)
C11 (GPa)
(Kgmm-2)
HK
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Table 2. The calculated mechanical parameters for SHOM crystal n
Bi x 10^-5
3.82
2.947
3.82
3.473
(Kgmm-2)
22.45
2.315
7.483
17.231
50
32.05
4.317
10.683
24.676
100
43.9
7.487
14.633
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25
3.82
4.275
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3.3.1 Hays-Kendall (HK) approach
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The nonlinear performance of the material with various load can be analytically employed using
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Hays Kendall approach [12]. The information about the Indentation Size Effect behavior of
(C.1)
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P = W + A1dn
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materials and the load dependence of hardness may be expressed by
where W indicates the minimum load to initiate plastic permanent deformation and A1 is a load-
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independent constant with the exponent of n = 3.82. W and A1 have been evaluated from the plot against load P and d2 is shown in Fig. 4(f). The negative resistance pressure from the graph declares the strong Reverse Indentation Size Effect (RISE) behavior of the crystal corresponds to the applied load. The corrected load independent hardness HHK can be calculated utilizing the relation,
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(C.2)
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HHK = 1854.4A1
Fig. 4(a) Hardness number (HV)
(b) Stiffness Constant (C11) (c) Yield strength (σy)
(d) Knoop Hardness number (e) Log d vs Log P
(f) d2 Vs load P
Moreover, the calculated resistance pressure (W) and load independent constant (A1) values are specified in Table 3.
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Table 3. Estimated Hay’s Kendall constant W, A1 and HHK for SHOM Results
Resistance pressure (W)
- 47.11 (g)
Load independent constant (A1)
0.0343 (g/μm2)
Corrected load independent hardness (HHK)
63.61 (g/μm2)
3.4 Laser Damage Threshold
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HK constant
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The LDT analysis is very essential for NLO crystals because when a high power laser is irradiated to the surface of the crystal it should withstand or it may limit its performance in NLO applications. This can be measured by single or multiple shot, mostly multiple shot mode is more
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preferable so that NLO crystals are notable for long duration repetitive mode for different optical applications.
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The grown SHOM crystal was polished and mounted on the crystal holder. A high power
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Nd:YAG laser beam was allowed to fall on the crystal surface. The energy of the laser beam was increased from 5 mJ for a time duration of 10 ns for all measurements to take place. The spot
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size of the beam was adjusted to be 1 mm and the observations are noted. As the energy increases, a small dot like mark was spotted on the crystal surface and was observed by an
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optical microscope. To view more clearly, same laser beam with high repetitive rate was irradiated at different spots on the same crystal at similar condition. The surface damage profile was observed clearly by an optical microscope. The surface damage threshold of the crystal was calculated using the formula [15], Power density Pd = E / τ A
(D.1)
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where E(mJ), τ(ns) and r(mm) represents energy, pulse width and radius of the spot respectively. The calculated surface damage was appraised to be 2.65 GW/cm2 which exhibits higher value compared to KDP (0.20 GW/cm2) and urea (1.50 GW/cm2) [16]. The NLO material with low laser damage threshold will rigorously limit the optical applications. Hence the grown material
radiation. 3.5 Thermal and Differential Thermal Analysis
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SHOM with high laser damage threshold value possess an excellent resistant to high power laser
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The thermal and differential thermal analysis were studied to understand about the melting point, decomposition, phase analysis and stability of the grown SHOM crystal. The powder sample was employed to thermal analyzer technique to assess the weight loss (TG) and change in energy (DTA) for the corresponding temperature. The TG-DTA study was examined
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using SII-NANO TECHNOLOGY (MODELTG/DTA6200) in the temperature range 50- 600˚C
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at a heating rate of 20˚C min-1 in an alumina crucible in a nitrogen atmosphere. The TG/DTA curve for the as grown semi organic crystal is depicted in Fig. 5. The examined curve assures a
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sharp endothermic peak at 134.7 0C which coincides with the melting point of the compound. Further two more endothermic transition occurs at 267.6 0C represents 43.2 % and 557.8 0C at
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12% weight loss respectively. The TGA curve illustrates the complete decomposition of the
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sample. The decomposition occurs in steps could be due to the decomposition and volatilization of the title compound [17]. Thus the results of TG-DTA, conveys the thermal stability and shows a vital applicant in nonlinear optical applications.
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Fig. 5 TG/DTA Curve for SHOM crystal
3.5 Linear and Nonlinear Optical Analysis
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3.5.1 Optical Absorbance Analysis
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The spectral examination of an UV – Visible spectrum of the grown SHOM crystal was carried out using LAMBDA-35 UV-Vis spectrophotometer in the range of 100 nm -1200 nm. The knowledge about band structure and impurity levels in solids are much essential to enhance the optical transparency of the grown crystal. The observed UV – Visible spectrum of SHOM is shown in Fig. 6(a).Generally, the higher absorption indicates the presence of flaws or impurities in the crystal. In SHOM, the lower cut off wavelength observed at 225 nm exhibits intense
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transparency in the entire visible region substantiates the materials effectiveness in the application for optoelectronics facilitating its suitability in the sector of nonlinear optics. The optical absorption coefficient (α) can be determined from the transmittance spectrum
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utilizing the relation [18], 2.3026 log(1 / T ) t
(E.1)
where, T is the transmittance (%), and t be the thickness of the sample (cm). A Tauc’s plot of
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(αhυ)2 verses Photon energy (hυ) in eV is shown in Fig. 6(b) has been plotted to elucidate the band gap energy value. The optical band gap energy Eg shows the intersection of the extrapolated line with the photon energy axis and was found to be 5.37 eV. As a consequence of this wide band gap, the grown crystal has a large transmittance in the visible region confirms the decrease
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of defect concentration [19]. The estimated large optical band gap suggests that the crystal
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acquire dielectric nature to stimulate polarization when intense radiation falls on it [20].
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Fig. 6(a) & 6(b) UV- Visible spectrum & Tauc’s plot – Band gap of SHOM crystal 3.5.2 Determination of Optical Parameters
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The various optical parameters are very essential to understand the materials potential towards
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nonlinear applications. The reflectance, extinction coefficient, refractive index, susceptibility measurements are carried out from absorption coefficient (α) gains knowledge to understand about the materials atomic structure, electronic band structure and electrical properties. The variation of Reflectance (R), Extinction coefficient (K) and Refractive index (n) shows a significant interactions between photon and electron.
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The extinction coefficient (K) and reflectance (R) associated to the absorption coefficient (α)is utilized from the relation [18],
4
(F.1)
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K
√
(F.2)
Fig. 7(a),(b) illustrates the variation of reflectance R, extinction coefficient K with respect to
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photon energy hν. The low reflectance and extinction coefficient predicts higher transmittance of
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the grown crystal shows remarkable applications in nonlinear optics.
Fig. 7(a) Photon energy hν verses Reflectance R and (b) Extinction coefficient (K)
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The Refractive index (n) can be evaluated directly from reflectance R, employing the relation [19]: 2 ( R 1) 3R *10 R 3 n 2( R 1)
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(F.3)
The interaction of light with matter is understand from the refractive index dispersion of the material. Fig. 8(a) portrays the change of refractive index n with the photon energy. The refractive index gradually decreases with photon energy. The refractive index of grown crystal
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was attained to be 1.589 in the transmission range. The optical parameters refractive index, reflectance and extinction coefficient reveals that the grown crystal is more transparent to transmit the light from 220 nm to 1100 nm. Hence the optical constants undoubtedly supportive
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to study the material’s suitability in the application of opto electronic devices [21].
n K 2 0 c 0 4
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2
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The electric susceptibility (χc) can be formulated using the relation [19],
(F.4)
Fig. 8(b) shows the variation of electric susceptibility with photon energy. Since the electrical
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susceptibility is greater than 1, the material can be easily polarized due to powerful intense
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incident light assures SHOM as an efficient nonlinear optical material [22].
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Fig. 8(a) & (b) Photon energy verses Refractive index & Electric Susceptibility 3.5.3 Z- Scan Analysis
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Z- Scan technique is a simple and accurate method to determine the nonlinear absorption and
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refractive index of crystals, thin films and liquid solutions by Shakebahae [23]. This is a standard single beam method for measuring the sign and magnitude of nonlinear absorption (β) and nonlinear refractive index (n2) and nonlinear susceptibility (χ3) which has widely accepted by nonlinear optics community due to a simplicity of interpretation. Materials with large nonlinearities are commonly focused on high speed optical switching devices [24].
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The third order nonlinear properties of the grown crystal can be measured using He – Ne laser (5mW, 632.8 nm) as a source with a beam diameter of 0.5 mm. The single Gaussian beam was directed through a convex lens with a focal length of 30 mm and the focal point is taken as Z = 0 [25]. The variation in far field transmittance beam intensity was measured through the closed
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aperture using a digital power meter. The nonlinear absorption and nonlinear refractive index directly affects the amplitude and phase of the applied field and can be measured by closed and open aperture method using Z Scan technique.
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From the results of Z-scan, the difference between the normalized valley and peak transmittance ΔTp-v can be determined by [24], | |
(G.1)
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where| | represents the on – axis phase shift at the focus. S is the linear transmittance aperture and is estimated by )
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⁄
(G.2)
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Here ra is the radius of the aperture and ωa be the beam radius at the aperture.
| |
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The on – axis phase shift | | is given by [24], (G.3)
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Where Leff = (1-e-αL) / α
Here L denotes the sample length, α represents the linear absorption coefficient, I0 be the laser beam intensity at focus Z=0 and k represents the wave number (k= 2π / λ).
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From the open aperture trace, the nonlinear absorption coefficient can be determined using the relation [24], √
(G.4)
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is the one valley value at the open aperture normalized transmittance Z-scan trace.
ZR = (K ω02 / 2) which determines the beam diffraction length, ω0 represents the waist radius of the beam. The value of nonlinear absorption coefficient β will be positive for two photon
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absorption and negative for saturation absorption. The real and imaginary part of nonlinear optical susceptibility is carried out using the experimentally determined value of n2 and β which
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is given by [24],
(G.6)
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)
(G.5)
Where ε0 and C represents the permittivity of free space in vacuum and the velocity of light in
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refractive index.
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vacuum respectively. The real part of susceptibility completely depends on the nonlinear
The absolute third order nonlinear optical susceptibility was estimated using the relation [24], |
(
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|
)
(
)
⁄
(G.7)
The negative nonlinearity of the sample shows transmittance peak followed by valley, similarly the positive nonlinearity shows the transmittance valley followed by peak. Fig. 9 illustrates the closed aperture profile for SHOM crystal shows peak followed by valley confirms negative nonlinear refractive index i.e. the presence of self – defocusing of the grown crystal. Fig. 10
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indicates the open aperture curve for SHOM crystal. The positive value of β clearly indicates the process of two photon absorption and is widely employed for optical power limiting applications [26]. Fig. 11 shows the Z- scan ratio of the SHOM crystal. Table 4 indicates the experimental results of the Z-scan technique for SHOM crystal. Eventually, the nonlinear absorption and
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nonlinear refraction is related to two photon absorption process and self-defocusing nature of SHOM respectively. Due to excellent nonlinear response it is concluded that it could be a potent candidate for NLO device fabrication.
Third order nonlinear properties
Measured values 5.99 x 10-8 cm2/W
Nonlinear refractive index (n2)
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Nonlinear absorption coefficient (β) Real susceptibility (χR (3)) Imaginary susceptibility (χI (3))
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Absolute susceptibility (χ3)
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Table 4: Third order nonlinear optical parameters from Z – scan for SHOM crystal
0.08 x 10-4 cm/W
8.458 x 10-6esu 0.494 x 10-6esu 8.472 x 10-6 esu
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Fig. 9 Closed aperture curve for SHOM crystal
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Fig. 10 Open aperture curve for SHOM crystal
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4. Conclusion
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Fig. 11 Z - Scan ratio of SHOM crystal
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Our investigation on good optical transparent semi organic Sodium Hydrogen Oxalate
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Monohydrate (SHOM) single crystal have been synthesized effectively and harvested successfully from the mother solution by slow solvent evaporation method. The single crystal XRD study declares the triclinic crystal system with a space group of Pī confirms the centrosymmetric nature of the grown material. The cell parameters were also analyzed and compared with the reported literature. The diverse vibrational assignments of SHOM were concluded applying FTIR instrumentation. Vickers microhardness analysis indicates the
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existence of reverse indentation size effect in the crystal thereby exhibiting the soft nature. The LDT experiment shown that the grown crystal possess an excellent resistant to high power laser radiation with a high threshold upto 2.65 GW/cm2 exhibit better compared with other organic and semi organic materials. The thermal stability and decomposition of SHOM are examined by
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TG/DTA analyses. Several optical parameters specifically transmittance, energy gap, reflectance, extinction coefficient, have been assessed by UV–Vis spectral study. Z-scan studies showed that the SHOM crystal possess self-defocusing nature with nonlinear absorption coefficient and nonlinear refractive index. The detailed characterization and optical nonlinearity attest its
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suitability and reliability in optoelectronics, photonics and optical limiting devices. Acknowledgement
The scientific supports rendered by sophisticated analytical instrument facility IITM, for support
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in single crystal XRD and FTIR is gratefully acknowledged. The facilities rendered by Department of Polymer and Nanoscience of BS Abdul Rahman University (BSAU), Chennai for
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providing thermal analysis measurement is gratefully thanked. The authors give their sincere
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thanks to St.Joseph’s College Trichy for providing the microhardness analysis.
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