- Email: [email protected]
A novel all optical 4×2 encoder switch based on photonic crystal ring resonators
Accepted Manuscript Title: A novel all optical 4×2 encoder switch based on photonic crystal ring resonators Author: Iman Ouahab Rafah PII: DOI: Reference:
S0030-4026(16)30530-7 http://dx.doi.org/doi:10.1016/j.ijleo.2016.05.080 IJLEO 57706
To appear in: Received date: Accepted date:
26-3-2016 24-5-2016
Please cite this article as: {http://dx.doi.org/ This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
A Novel All Optical 4x2 Encoder Switch Based on Photonic Crystal Ring Resonators Iman.OUAHAB*, Rafah. Naoum* * Telecommunication and Digital Signal Processing Laboratory, Faculty of technology, Department of Electronics, University Djillali Liabes, Sidi-Bel-Abbes22000, Algeria. [email protected] [email protected]
Abstract: A novel approach to design an all optical 4x2 encoder is proposed by employing Kerr effect in 2D square lattice of silicon rods in photonic crystals. The main operation of device is based on the concept of all optical switch. Our proposed encoder consists of two nonlinear ring resonators with L-shape waveguides, characterized by the same resonant wavelength, embedded between four parallel waveguides. The operation of encoder at third optical window (𝜆𝑐 = 1.5478𝜇𝑚 ) is verified with Finite Difference Time Domain (FDTD) and Plane Wave Expansion method (PWE) .The proposed structure is simple with clear operating principal, low power consumption , and ultra-small size (18.5µm x13µm) compared with previously reported encoders , therefore facilitate its integration into all optical communication systems. Key words: Photonic crystals, all optical switch, Kerr effect, ring Resonator, all optical encoder, FDTD, PWE.
1. Introduction: Currently, the challenge of diverse researches is to design all optical devices in photonic crystals for all optical signal processing, in order to avoid the complexities and speed limitation of optical/electrical (O/E) conversion [1]. So that, many technologies have been reported to design all optical encoders, practical logic gate in mouse, scanner, printer, optical disk drive and all-optical programmable logic controller (PLC)[2]. Ricardo et al. depicted an all optical encoder based on the Semiconductor Laser Amplifier Loop Mirror (SLALOM) configuration [3,4].Chattopadhyay and Nath have demonstrated all-optical encoders using the polarization scheme of radix 2 and radix 4[5]. Based on photonic crystals, many all optical encoders have been designed. Lee et al.
supposed 4x2 all-optical encoder based on the combination of both line defect Y branch and coupler photonic crystal waveguides [6].
[7] All-optical digital 4 × 2 encoder exploiting 2D photonic crystal ring resonators is
presented by A. Moniem[4],where the total size of the proposed device is equal to (35 μm × 35μm). Alipour-Banaei et al. have proposed 4x2 optical encoder by employing the self-collimation effect in 2D photonic crystals with an area of about (69 μm × 55 μm) [2]. In this paper, the proposed 4x2 encoder switch is simple to fabricate and operate with ultracompact size of (18.5µm x13µm) and low power consumption. The main operation of device is based on two optical switches, where the structure of the switch is a photonic crystal ring resonator
(PhCRR) formed by a nonlinear RR with L shape waveguide created by embedded nonlinear refractive index rods of Polystyrene (PS). PWE method was used to extract the appropriate Photonic Band Gap (PBG) and FDTD method for investigating the light behavior of encoder.
2. Numerical Method: In this paper, we have used the Plane Wave Expansion (PWE) method to extract the appropriate Photonic Band Gap (PBG) of the fundamental structure by analyzing the band gap map and dispersion diagram. For investigating the light behavior, resonance and transmission spectra, we have applied 2D nonlinear finite-difference time-domain (NL-FDTD) method with perfectly matched layer boundary conditions (PML) [8]. , where a Gaussian pulse is used to excite the fundamental mode along the x direction with a spatial step ∆𝑥 = ∆𝑧 = 𝑎⁄16 𝜇𝑚 , the sampling time ∆𝑡 = 0.01𝑓𝑠 is selected to ensure numerical stability of the algorithm, by: ∆t ≤
1 1 2
1 2
(1)
c√(∆x) + (∆y)
3. Kerr Nonlinearity: To design the all optical switch, we have exploited nonlinear Kerr properties of Polystyrene (PS). Important third order nonlinear susceptibility, higher laser damage threshold, fast nonlinear optical response time and low cost persuaded us to choose this organic polymer materiel for our device. For Kerr nonlinear mediumElectric field (E), electric displacement (D) and nonlinear polarization (PNL) are associated as follows [9]: 𝐷 = 𝜀0 𝜀𝐿 𝐸 + 𝑃𝑁𝐿 𝑃𝑁𝐿 = 𝜀0 𝜒 (3) (|𝐸|2 )𝐸
(2) (3)
By replacing (3) in (2): 𝐷 = 𝜀0 𝐸[𝜀𝐿 + 𝜒 (3) (|𝐸|2 )] (4) (3) 2 𝜀𝑁𝐿 = 𝜀𝐿 + 𝜒 |𝐸| (5) 𝜀𝐿 and 𝜀𝑁𝐿 are linear and nonlinear permittivities respectively and 𝜒 (3) is the third order nonlinear susceptibility. For PS 𝜀𝐿 = 𝑛𝐿2 =2.5281 and 𝜒 (3) = 1.15 × 10−12 𝑐𝑚2 /𝑊 [10].From (Equat.5) we deduce that nonlinear Kerr effect induce dependency of polystyrene permittivity to field intensity.
4. Design of the proposed structure: The initial structure proposed for designing the all optical encoder switch is a 34*24 square array of silicon (Si) rods with refractive index of 3.5 in air. We exploit the gap-map diagram for different value of (r/a) ratio in order to select the proper values of r and a. We deduce from Fig.2 that the structure supports the appearance of PBG in TM mode and decrease by increasing the ratio r/a. In order to have a large band gap we choose r=0.18a, where a=540nm is the lattice constant .
4.1.
All Optical Switch Design:
The proposed switch is a photonic crystal ring resonator (PhCRR) formed by an input wave-guide (Iin) adjacent to a nonlinear RR with a radius of 3a, created by removing Si rods and embedded rods of Polystyrene (PS) (marked in dark blue) with a radius of 0.32a. After that we create the L-shape waveguide near to RR which represents the drop waveguide as illustrated in Fig.4. Scatterers are placed at corners of the quasi-square ring resonators and waveguides for improving the transmission spectra of the structure [11, 12, 13, 14, 15] in linear status to 92.1% as illustrated For the linear status, when the switch is excited from port ‘Iin’,drop occurs at 𝜆𝑐 =1.5478 µm and will exit from port ‘O1’ due to the resonant effect of ring resonator. We perform 2D nonlinear finite-difference time-domain (FDTD) simulations for the TM mode at the steady state [16]. For that, we launch continuous-wave (CW) signal with a resonant wavelength 𝜆𝑐 and a power of 0.1W into the bus waveguide. The output power level at steady state from port ‘O1’ and ‘O2’ can be achieved. We vary the input power (Pin) and measure the output power at steady state. The variation of normalized power of output ‘O 1’ and ‘O2’ as function of incident power ‘Iin’ is shown in Fig.6, which represent that the switching threshold of the switch is 0.5W. If we apply a low signal power (Iin˂0.5W), the RR resonates at 𝜆𝑐 and will exit from port ‘O1’ where the normalized power is more than 80%. For a high power signal ((Iin˃0.5W) ,due to Kerr effect the refractive index of PS rods increase , 𝜆𝑐 varies and will be red-shifted, therefore, no signal will be coupled to ring resonator and all input power signal will exit from port ‘O2’ where the normalized power is more than 90%. Consequently, the proposed switch has two working states, where their behavior is illustrated by electric field distribution in Fig.7 .If we consider 𝜆𝑐
as the operational
wavelength of the device, in linear case, Iin resonate with RR and exit from ‘O1’, it means that the switch is ‘ON’Fig.7(a).According to Fig.7(b), if we launch a high power intensity no signal exit from drop waveguide and all the optical signal will go toward port ‘O2’ , therefore, the device switch to ‘OFF’ state.
4.2.
All Optical Encoder Design:
An encoder is a logical device that converts 2n input signals to N bit coded outputs. For (4x2) all optical encoder, the output signal is (00), (01), (10), (11) depending on the four input signals (0001), (0010), (0100), (1000) as show in truth table (Table.1). The logic circuit of encoder has four inputs (I0, I1, I2, I3) and two binary outputs (O1, O2) as shown in Fig.8.
Our proposed 4x2 encoder consists of two nonlinear ring resonators with L-shape waveguides, characterized by the same resonant wavelength, embedded between four parallel waveguides as illustrated in Fig.9.
5. Optical Encoder operation and simulation results: For trying the process of the proposed encoder, we exploit FDTD method and simulate the four inputs signal mentioned in the truth table under TM polarized Gaussian continuous wave with a wavelength of 1.5478µm.If the normalized intensity of output signal is above 45% the logic level is considered 1 and if it is below 5%, it is for logic 0 as demonstrated in Fig.10.
The optical encoder is based on the principle operation of two optical switches, where each one is formed by a nonlinear ring resonator with L waveguide. To explain the operation of the device, we consider a sequence (I0, I1, I2, and I3) of input signals, where I0 and I2 are excited with low power (Iin˂0.5W) then again I1and I3 are pumped with high power signal (Iin˃0.5W)[7]: Case 1:At I3=1,I2=0, I1=0 and I0=0, as shown in Fig.11(a), the input light has a high power what means that the resonant wavelength of RR red-shift due to Kerr effect , as a result I3exit from port ‘O2’ and will not couple with the ring. Case 2:At I3=0,I2=1, I1=0 and I0=0, as shown in Fig.11(b),
˂45%
Case 3:At I3=0,I2=0, I1=1and I0=0, as shown in Fig.11(c), since I1 have a high power , no signal will exit from drop waveguide and all the optical signal will go toward port ‘O1’ Case 4: At I3=0,I2=0, I1=0 and I0=1, as shown in Fig .11(d) the signal is totally reflected, there are no outputs.
Conclusion: An all optical 4x2 encoder operating in third optical window is proposed and demonstrated. Based on the concept of all optical switch with Kerr effect, the device is composed of Si rods in air with two nonlinear ring resonators created by embedding rods of PS. The operation of encoder is simulated using FDTD and PWE method. The proposed structure is ultra-small with area equal to (18.5µm x13µm),simple to fabricate with clear operating principal compared with other complex structures and low power consumption, which prove that this encoder is proper for all optical integrated circuits.
References: [1] L.D Haret, T.Tanabe, E.Kuramochi, M.Notomi, Extremely low power optical bistability in silicon demonstrated using 1Dphotonic crystal nanocavity, Opt. Express 17 (2009)21108-21117. [2] H. Alipour-Banaei, M.G. Rabati, P. Abdollahzadeh-Badelbou, F. Mehdizadeh, Application of SelfCollimated Beams to Realization of All Optical Photonic Crystal Encoder, Physica E: Low-dimensional Systems and Nanostructures (2015). http://dx.doi.org/10.1016/j.physe.2015.08.011 [3] R.M. Ribeiro, F. Lucarz, B. Fracasso, , Proposal and Design of an All-optical Encoder for Digitizing Radioover-Fibre Transceivers. Network and Optical Communications (NOC), 18 th European Conference on Optical Cabling and Infrastructure, Graz, Austria, 2013. [4] T.A. Moniem, All-optical digital 4 × 2 encoder based on 2D photonic crystal ring resonators, Journal of Modern Optics(2015), DOI:10.1080/09500340.2015.1094580 [5] T. Chattopadhyay, J. Nath, J. Opt. A: Pure Appl. Opt. 11 (2009) 075501. [6] Lee, K.-Y., Yang, Y.-C., Yen, -J.L., Lee W.-Y.,: The Designs of 4 × 2 Encoder Based on Photonic Crystals.Communications and Photonics Conference and Exhibition (ACP) Asia, Shanghai, China, 2009.
[7] M. Hassangholizadeh-Kashtiban, R. Sabbaghi-Nadooshan, , H. Alipour-Banaei, , A Novel all Optical Reversible 4x2 Encoder based on photonic crystals, Optik - International Journal for Light and Electron Optics (2015),http://dx.doi.org/10.1016/j.ijleo.2015.05.140. [8]
In
this
paper,
Fullwave
commercial
software
developed
by
Rsoft
Design
Group
(http://www.rsoftdesign.com) is used for linear and nonlinear FDTD simulations, v.2014.09, license 16849450. [9] Agrawal, G.P., Nonlinear Fiber Optics,3rdedn,Academic Press ,Sandiego,CA (2001).
[10] Z-Y. Li, Z-M Meng, Polystyrene Kerr nonlinear photonic crystals for building ultrafast optical switching and logic devices , Mater. Chem. C, 2 (2014) 783-800. [11]
[12] Tahereh Ahmadi Tameh, Babak Memarzadeh Isfahani, Nosrat Granpayeh, Alireza Maleki Javan, Improving the performance of all-optical switching based on nonlinear photonic crystal microring resonators, Int. J. Electron. Commun. (AEÜ) 65 (2011) 281–287. [13] Tamer A. Moniem , All optical active high decoder using integrated 2D square lattice photonic crystals, Journal of Modern Optics (2015), DOI: 10.1080/09500340.2015. [14] S. Serajmohammadi, H. Alipour-Banaei, , F. Mehdizadeh, All optical decoder switch based on photonic crystal ring resonators. Opt. Quant. Electron. 47, 1109–1115 (2015) [15] V. Dinesh Kumar, T. Srinivas, A. Selvarajan, Investigation of ring resonators in photonic Crystal circuits, Photon Nanostruct, 2 (2004) 199–206. [16] Z-H. Zhu, W.M. Ye , J-R. Ji, X-D. Yuan, C. Zen, High-contrast light-by-light switching and AND gate based on nonlinear photonic crystals, Opt. Express, 14(2006)1783-1788.
Si rods Air
Fig.1: The initial structure.
Fig.2: Gap-Map diagram of the initial structure.
Fig.3: The TE/TM band diagram for the selected parameters (r=0.18a, a=540nm), Appearance of TM band gap in the range (0.293 < 𝑎⁄𝜆 < 0.445) which corresponds to (1.2135𝜇𝑚 < 𝜆 < 1.843𝜇𝑚).
O1 O2
Iin
O2
PS (r= 0.32a)
O1
Fig.4 :Schematic of the proposed all optical Switch.
Fig.5 :Linear transmission spectra of PhCRR.
Fig.6: Transmission as function of the incident powers at steady states.
(a)
(b)
Fig.7: ((Iin˂0.5W)
(Iin˃0.5W).
𝜆𝑐 =1.5478 µm
I0
O1
I1
O2
I2 I3
Fig.8: The logic circuit of encoder
, Fig.9: The structure of the proposed All-optical 4 × 2 Encoder in 2D Photonic Crystal.
45%
Logic 1
5%
Logic 0 Fig.10: Transmission level ranges.
(a)
(b)
0
0 0
0
1
0 1
1
(d)
0
1 1
0
0
1
0
(c)
1
1
0
0
0
0
0
0
0
Fig.11: Electric field pattern of optical 4 × 2 Encoder for different cases of inputs: (a) :( 0001), (b): (0010), ,(c):(0100), (d):(1000).
Table.1: The Truth table of 4 × 2 encoder.
I0 1 0 0 0
I1 0 1 0 0
I2 0 0 1 0
I3 0 0 0 1
O1 0 1 1 0
O2 0 0 1 1
S0030-4026(16)30530-7 http://dx.doi.org/doi:10.1016/j.ijleo.2016.05.080 IJLEO 57706
To appear in: Received date: Accepted date:
26-3-2016 24-5-2016
Please cite this article as: {http://dx.doi.org/ This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
A Novel All Optical 4x2 Encoder Switch Based on Photonic Crystal Ring Resonators Iman.OUAHAB*, Rafah. Naoum* * Telecommunication and Digital Signal Processing Laboratory, Faculty of technology, Department of Electronics, University Djillali Liabes, Sidi-Bel-Abbes22000, Algeria. [email protected] [email protected]
Abstract: A novel approach to design an all optical 4x2 encoder is proposed by employing Kerr effect in 2D square lattice of silicon rods in photonic crystals. The main operation of device is based on the concept of all optical switch. Our proposed encoder consists of two nonlinear ring resonators with L-shape waveguides, characterized by the same resonant wavelength, embedded between four parallel waveguides. The operation of encoder at third optical window (𝜆𝑐 = 1.5478𝜇𝑚 ) is verified with Finite Difference Time Domain (FDTD) and Plane Wave Expansion method (PWE) .The proposed structure is simple with clear operating principal, low power consumption , and ultra-small size (18.5µm x13µm) compared with previously reported encoders , therefore facilitate its integration into all optical communication systems. Key words: Photonic crystals, all optical switch, Kerr effect, ring Resonator, all optical encoder, FDTD, PWE.
1. Introduction: Currently, the challenge of diverse researches is to design all optical devices in photonic crystals for all optical signal processing, in order to avoid the complexities and speed limitation of optical/electrical (O/E) conversion [1]. So that, many technologies have been reported to design all optical encoders, practical logic gate in mouse, scanner, printer, optical disk drive and all-optical programmable logic controller (PLC)[2]. Ricardo et al. depicted an all optical encoder based on the Semiconductor Laser Amplifier Loop Mirror (SLALOM) configuration [3,4].Chattopadhyay and Nath have demonstrated all-optical encoders using the polarization scheme of radix 2 and radix 4[5]. Based on photonic crystals, many all optical encoders have been designed. Lee et al.
supposed 4x2 all-optical encoder based on the combination of both line defect Y branch and coupler photonic crystal waveguides [6].
[7] All-optical digital 4 × 2 encoder exploiting 2D photonic crystal ring resonators is
presented by A. Moniem[4],where the total size of the proposed device is equal to (35 μm × 35μm). Alipour-Banaei et al. have proposed 4x2 optical encoder by employing the self-collimation effect in 2D photonic crystals with an area of about (69 μm × 55 μm) [2]. In this paper, the proposed 4x2 encoder switch is simple to fabricate and operate with ultracompact size of (18.5µm x13µm) and low power consumption. The main operation of device is based on two optical switches, where the structure of the switch is a photonic crystal ring resonator
(PhCRR) formed by a nonlinear RR with L shape waveguide created by embedded nonlinear refractive index rods of Polystyrene (PS). PWE method was used to extract the appropriate Photonic Band Gap (PBG) and FDTD method for investigating the light behavior of encoder.
2. Numerical Method: In this paper, we have used the Plane Wave Expansion (PWE) method to extract the appropriate Photonic Band Gap (PBG) of the fundamental structure by analyzing the band gap map and dispersion diagram. For investigating the light behavior, resonance and transmission spectra, we have applied 2D nonlinear finite-difference time-domain (NL-FDTD) method with perfectly matched layer boundary conditions (PML) [8]. , where a Gaussian pulse is used to excite the fundamental mode along the x direction with a spatial step ∆𝑥 = ∆𝑧 = 𝑎⁄16 𝜇𝑚 , the sampling time ∆𝑡 = 0.01𝑓𝑠 is selected to ensure numerical stability of the algorithm, by: ∆t ≤
1 1 2
1 2
(1)
c√(∆x) + (∆y)
3. Kerr Nonlinearity: To design the all optical switch, we have exploited nonlinear Kerr properties of Polystyrene (PS). Important third order nonlinear susceptibility, higher laser damage threshold, fast nonlinear optical response time and low cost persuaded us to choose this organic polymer materiel for our device. For Kerr nonlinear mediumElectric field (E), electric displacement (D) and nonlinear polarization (PNL) are associated as follows [9]: 𝐷 = 𝜀0 𝜀𝐿 𝐸 + 𝑃𝑁𝐿 𝑃𝑁𝐿 = 𝜀0 𝜒 (3) (|𝐸|2 )𝐸
(2) (3)
By replacing (3) in (2): 𝐷 = 𝜀0 𝐸[𝜀𝐿 + 𝜒 (3) (|𝐸|2 )] (4) (3) 2 𝜀𝑁𝐿 = 𝜀𝐿 + 𝜒 |𝐸| (5) 𝜀𝐿 and 𝜀𝑁𝐿 are linear and nonlinear permittivities respectively and 𝜒 (3) is the third order nonlinear susceptibility. For PS 𝜀𝐿 = 𝑛𝐿2 =2.5281 and 𝜒 (3) = 1.15 × 10−12 𝑐𝑚2 /𝑊 [10].From (Equat.5) we deduce that nonlinear Kerr effect induce dependency of polystyrene permittivity to field intensity.
4. Design of the proposed structure: The initial structure proposed for designing the all optical encoder switch is a 34*24 square array of silicon (Si) rods with refractive index of 3.5 in air. We exploit the gap-map diagram for different value of (r/a) ratio in order to select the proper values of r and a. We deduce from Fig.2 that the structure supports the appearance of PBG in TM mode and decrease by increasing the ratio r/a. In order to have a large band gap we choose r=0.18a, where a=540nm is the lattice constant .
4.1.
All Optical Switch Design:
The proposed switch is a photonic crystal ring resonator (PhCRR) formed by an input wave-guide (Iin) adjacent to a nonlinear RR with a radius of 3a, created by removing Si rods and embedded rods of Polystyrene (PS) (marked in dark blue) with a radius of 0.32a. After that we create the L-shape waveguide near to RR which represents the drop waveguide as illustrated in Fig.4. Scatterers are placed at corners of the quasi-square ring resonators and waveguides for improving the transmission spectra of the structure [11, 12, 13, 14, 15] in linear status to 92.1% as illustrated For the linear status, when the switch is excited from port ‘Iin’,drop occurs at 𝜆𝑐 =1.5478 µm and will exit from port ‘O1’ due to the resonant effect of ring resonator. We perform 2D nonlinear finite-difference time-domain (FDTD) simulations for the TM mode at the steady state [16]. For that, we launch continuous-wave (CW) signal with a resonant wavelength 𝜆𝑐 and a power of 0.1W into the bus waveguide. The output power level at steady state from port ‘O1’ and ‘O2’ can be achieved. We vary the input power (Pin) and measure the output power at steady state. The variation of normalized power of output ‘O 1’ and ‘O2’ as function of incident power ‘Iin’ is shown in Fig.6, which represent that the switching threshold of the switch is 0.5W. If we apply a low signal power (Iin˂0.5W), the RR resonates at 𝜆𝑐 and will exit from port ‘O1’ where the normalized power is more than 80%. For a high power signal ((Iin˃0.5W) ,due to Kerr effect the refractive index of PS rods increase , 𝜆𝑐 varies and will be red-shifted, therefore, no signal will be coupled to ring resonator and all input power signal will exit from port ‘O2’ where the normalized power is more than 90%. Consequently, the proposed switch has two working states, where their behavior is illustrated by electric field distribution in Fig.7 .If we consider 𝜆𝑐
as the operational
wavelength of the device, in linear case, Iin resonate with RR and exit from ‘O1’, it means that the switch is ‘ON’Fig.7(a).According to Fig.7(b), if we launch a high power intensity no signal exit from drop waveguide and all the optical signal will go toward port ‘O2’ , therefore, the device switch to ‘OFF’ state.
4.2.
All Optical Encoder Design:
An encoder is a logical device that converts 2n input signals to N bit coded outputs. For (4x2) all optical encoder, the output signal is (00), (01), (10), (11) depending on the four input signals (0001), (0010), (0100), (1000) as show in truth table (Table.1). The logic circuit of encoder has four inputs (I0, I1, I2, I3) and two binary outputs (O1, O2) as shown in Fig.8.
Our proposed 4x2 encoder consists of two nonlinear ring resonators with L-shape waveguides, characterized by the same resonant wavelength, embedded between four parallel waveguides as illustrated in Fig.9.
5. Optical Encoder operation and simulation results: For trying the process of the proposed encoder, we exploit FDTD method and simulate the four inputs signal mentioned in the truth table under TM polarized Gaussian continuous wave with a wavelength of 1.5478µm.If the normalized intensity of output signal is above 45% the logic level is considered 1 and if it is below 5%, it is for logic 0 as demonstrated in Fig.10.
The optical encoder is based on the principle operation of two optical switches, where each one is formed by a nonlinear ring resonator with L waveguide. To explain the operation of the device, we consider a sequence (I0, I1, I2, and I3) of input signals, where I0 and I2 are excited with low power (Iin˂0.5W) then again I1and I3 are pumped with high power signal (Iin˃0.5W)[7]: Case 1:At I3=1,I2=0, I1=0 and I0=0, as shown in Fig.11(a), the input light has a high power what means that the resonant wavelength of RR red-shift due to Kerr effect , as a result I3exit from port ‘O2’ and will not couple with the ring. Case 2:At I3=0,I2=1, I1=0 and I0=0, as shown in Fig.11(b),
˂45%
Case 3:At I3=0,I2=0, I1=1and I0=0, as shown in Fig.11(c), since I1 have a high power , no signal will exit from drop waveguide and all the optical signal will go toward port ‘O1’ Case 4: At I3=0,I2=0, I1=0 and I0=1, as shown in Fig .11(d) the signal is totally reflected, there are no outputs.
Conclusion: An all optical 4x2 encoder operating in third optical window is proposed and demonstrated. Based on the concept of all optical switch with Kerr effect, the device is composed of Si rods in air with two nonlinear ring resonators created by embedding rods of PS. The operation of encoder is simulated using FDTD and PWE method. The proposed structure is ultra-small with area equal to (18.5µm x13µm),simple to fabricate with clear operating principal compared with other complex structures and low power consumption, which prove that this encoder is proper for all optical integrated circuits.
References: [1] L.D Haret, T.Tanabe, E.Kuramochi, M.Notomi, Extremely low power optical bistability in silicon demonstrated using 1Dphotonic crystal nanocavity, Opt. Express 17 (2009)21108-21117. [2] H. Alipour-Banaei, M.G. Rabati, P. Abdollahzadeh-Badelbou, F. Mehdizadeh, Application of SelfCollimated Beams to Realization of All Optical Photonic Crystal Encoder, Physica E: Low-dimensional Systems and Nanostructures (2015). http://dx.doi.org/10.1016/j.physe.2015.08.011 [3] R.M. Ribeiro, F. Lucarz, B. Fracasso, , Proposal and Design of an All-optical Encoder for Digitizing Radioover-Fibre Transceivers. Network and Optical Communications (NOC), 18 th European Conference on Optical Cabling and Infrastructure, Graz, Austria, 2013. [4] T.A. Moniem, All-optical digital 4 × 2 encoder based on 2D photonic crystal ring resonators, Journal of Modern Optics(2015), DOI:10.1080/09500340.2015.1094580 [5] T. Chattopadhyay, J. Nath, J. Opt. A: Pure Appl. Opt. 11 (2009) 075501. [6] Lee, K.-Y., Yang, Y.-C., Yen, -J.L., Lee W.-Y.,: The Designs of 4 × 2 Encoder Based on Photonic Crystals.Communications and Photonics Conference and Exhibition (ACP) Asia, Shanghai, China, 2009.
[7] M. Hassangholizadeh-Kashtiban, R. Sabbaghi-Nadooshan, , H. Alipour-Banaei, , A Novel all Optical Reversible 4x2 Encoder based on photonic crystals, Optik - International Journal for Light and Electron Optics (2015),http://dx.doi.org/10.1016/j.ijleo.2015.05.140. [8]
In
this
paper,
Fullwave
commercial
software
developed
by
Rsoft
Design
Group
(http://www.rsoftdesign.com) is used for linear and nonlinear FDTD simulations, v.2014.09, license 16849450. [9] Agrawal, G.P., Nonlinear Fiber Optics,3rdedn,Academic Press ,Sandiego,CA (2001).
[10] Z-Y. Li, Z-M Meng, Polystyrene Kerr nonlinear photonic crystals for building ultrafast optical switching and logic devices , Mater. Chem. C, 2 (2014) 783-800. [11]
[12] Tahereh Ahmadi Tameh, Babak Memarzadeh Isfahani, Nosrat Granpayeh, Alireza Maleki Javan, Improving the performance of all-optical switching based on nonlinear photonic crystal microring resonators, Int. J. Electron. Commun. (AEÜ) 65 (2011) 281–287. [13] Tamer A. Moniem , All optical active high decoder using integrated 2D square lattice photonic crystals, Journal of Modern Optics (2015), DOI: 10.1080/09500340.2015. [14] S. Serajmohammadi, H. Alipour-Banaei, , F. Mehdizadeh, All optical decoder switch based on photonic crystal ring resonators. Opt. Quant. Electron. 47, 1109–1115 (2015) [15] V. Dinesh Kumar, T. Srinivas, A. Selvarajan, Investigation of ring resonators in photonic Crystal circuits, Photon Nanostruct, 2 (2004) 199–206. [16] Z-H. Zhu, W.M. Ye , J-R. Ji, X-D. Yuan, C. Zen, High-contrast light-by-light switching and AND gate based on nonlinear photonic crystals, Opt. Express, 14(2006)1783-1788.
Si rods Air
Fig.1: The initial structure.
Fig.2: Gap-Map diagram of the initial structure.
Fig.3: The TE/TM band diagram for the selected parameters (r=0.18a, a=540nm), Appearance of TM band gap in the range (0.293 < 𝑎⁄𝜆 < 0.445) which corresponds to (1.2135𝜇𝑚 < 𝜆 < 1.843𝜇𝑚).
O1 O2
Iin
O2
PS (r= 0.32a)
O1
Fig.4 :Schematic of the proposed all optical Switch.
Fig.5 :Linear transmission spectra of PhCRR.
Fig.6: Transmission as function of the incident powers at steady states.
(a)
(b)
Fig.7: ((Iin˂0.5W)
(Iin˃0.5W).
𝜆𝑐 =1.5478 µm
I0
O1
I1
O2
I2 I3
Fig.8: The logic circuit of encoder
, Fig.9: The structure of the proposed All-optical 4 × 2 Encoder in 2D Photonic Crystal.
45%
Logic 1
5%
Logic 0 Fig.10: Transmission level ranges.
(a)
(b)
0
0 0
0
1
0 1
1
(d)
0
1 1
0
0
1
0
(c)
1
1
0
0
0
0
0
0
0
Fig.11: Electric field pattern of optical 4 × 2 Encoder for different cases of inputs: (a) :( 0001), (b): (0010), ,(c):(0100), (d):(1000).
Table.1: The Truth table of 4 × 2 encoder.
I0 1 0 0 0
I1 0 1 0 0
I2 0 0 1 0
I3 0 0 0 1
O1 0 1 1 0
O2 0 0 1 1