In-line microfiber MZI operating at two sides of the dispersion turning point for ultrasensitive RI and temperature measurement

Journal Pre-proof In-line microfiber MZI operating at two sides of the dispersion turning point for ultrasensitive RI and temperature measurement Yong Zhao, Feng Xia, Yun Peng

PII:

S0924-4247(19)31427-X

DOI:

https://doi.org/10.1016/j.sna.2019.111754

Reference:

SNA 111754

To appear in:

Sensors and Actuators: A. Physical

Received Date:

18 August 2019

Revised Date:

29 October 2019

Accepted Date:

12 November 2019

Please cite this article as: Zhao Y, Xia F, Peng Y, In-line microfiber MZI operating at two sides of the dispersion turning point for ultrasensitive RI and temperature measurement, Sensors and Actuators: A. Physical (2019), doi: https://doi.org/10.1016/j.sna.2019.111754

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. 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. © 2019 Published by Elsevier.

In-line microfiber MZI operating at two sides of the dispersion turning point for ultrasensitive RI and temperature measurement

Yong Zhao1,2), Feng Xia2), Yun Peng2)

1

State Key Laboratory of Synthetical Automation for Process Industries, Shenyang, 110819, China

2

College of Information Science and Engineering, Northeastern University, Shenyang, 110819, China

author: Yong Zhao

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*Corresponding

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Electronic mail: [email protected]

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Graphical abstract



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Schematics of the bare and the PDMS-coated in-line microfiber MZI for RI and temperature sensing are shown in Fig. 1 (a) and Fig. 1 (b), respectively. The microfiber MZI which is fabricated by non-adiabatically tapering a single mode fiber is composed of two abrupt tapered regions and a uniform waist region. When the fundamental HE11 mode is propagating through the first abrupt tapered region, only symmetrical high order modes (HE1m) can be excited owing to the symmetry of the abrupt tapered regions. Besides the fundamental HE11 mode, only the high order HE12 mode is excited by the fabricated microfiber whose taper waist diameter is 4.8 μm. The mode profiles of HE11 mode and HE12 mode are shown in Fig. 1(c) and Fig. 1(d). These two modes interfere with each other at the second abrupt tapered region, forming dual-path interference.



An ultrahigh RI sensitivity of 24209 nm/RIU and a high temperature sensitivity of -2.47 nm/℃ are experimentally

Highlights

An in-line microfiber MZI is demonstrated for ultrasensitive surrounding RI and temperature measurement.

achieved.

Abstract An in-line microfiber Mach-Zehnder interferometer (MZI) is demonstrated for ultrasensitive refractive index (RI) and temperature measurement by operating at two sides of the dispersion turning point (DTP). An ultrahigh RI sensitivity of 24209 nm/RIU (RI unit) around 1.3320 and a high temperature sensitivity of -2.47 nm/℃ are experimentally achieved by a microfiber MZI with taper waist diameter of about 4.8 μm. By embedding this microfiber MZI into polydimethylsiloxane (PDMS), the temperature sensitivity is improved from -2.47 nm/℃ to about 8.33 nm/℃. The positive temperature sensitivity of this PDMS-coated microfiber MZI and the negative thermo-optic coefficient of PDMS show that this microfiber MZI has a negative RI sensitivity around the material RI of PDMS (about 1.405), which indicates that the microfiber MZI works at two sides of the DTP for RI measurement and temperature measurement. The PDMS-coated microfiber MZI could achieve a

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temperature measurement resolution of about 0.0024 ℃ if the resolution of the optical spectrum analyzer were 0.02 nm, making it suitable for temperature measurement applications with high precision requirement. The bare microfiber MZI is promising for liquid analytical measurement in fields like biochemistry for its advantages of ultrahigh sensitivity, small size,

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and little sample consumption.

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Keywords: Ultrasensitive optical fiber sensor, microfiber Mach-Zehnder interferometer, dispersion turning point; refractive index measurement; temperature measurement.

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1. Introduction

can achieve high RI sensitivities of thousands nm/RIU [10],

liquid refractive index (RI) [1], temperature [2], relative

however, the bandwidth of the resonance spectrum is very

humidity [3], magnetic field [4], and other parameters

broad and the resolution of the optical spectrum analyzer is

measurement owing to the advantages of high sensitivity,

too low, making the RI measurement precision and

small size, and fast response. The liquid RI sensing

detection limit are not ideal. Although high RI sensitivities

characteristics of optical fiber sensors is the basis of

can be achieved by LPGs which operate around dispersion

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Optical fiber sensors have been widely studied for

turning point (DTP) [11], the fabrication requirements of

temperature [2], [5], relative humidity [3], [6], magnetic

LPGs with DTP are very strict and the grating fabrication

field [4], [7] and biomedical parameters [8], etc. Achieving

devices like femtosecond laser are extremely expensive.

high sensitivity has become one of the hottest goals of

Instead, microfiber-based sensors can strongly interact with

optical fiber liquid RI-related sensors, so as to meet the

surrounding environment owing to the thin diameter and the

requirements of high sensitivity and low detection limit in

strong

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measurement for liquid RI-related parameters, such as

evanescent,

generating

sensitivities.

extremely

Microfiber-based

high

RI

practical applications. The optical fiber RI sensors mainly

measurement

sensors,

include Mach-Zehnder interferometers (MZIs), long-period

including microfiber MZIs [12]-[13], microfiber Sagnac

fiber gratings (LPGs), and surface plasmon resonance (SPR)

interferometers [14]-[15], microfiber couplers [16]-[17], and

sensors, etc. The structures of in-line MZIs are various and

microfiber resonators [18]-[19], and other structures, have

flexible, including offset-splicing structure, taper structure,

attracted lots of researching interests owing to the

special fiber like photonic crystal fiber, etc. [9]. However,

superiorities in very small size, convenient fabrication,

the RI sensitivities of the normal in-line MZIs are usually

outstanding sensitivity, and economical fabrication cost.

only hundreds of nm/RI unit (RIU), which are limited by the

Owing to the strong evanescent field, microfiber-based

weak evanescent field of the in-line MZIs [9]. SPR sensors

sensors usually have very high sensitivity and have been

widely

investigated

for

salinity

temperature

measurement

measurement

[6],

refractive

index

magnetic and

[5], field

temperature

measurement relative

humidity

measurement dual

℃ if the resolution of the optical spectrum analyzer were

[20],

0.02 nm.

[7],

2. Sensing principle and simulation

parameters

2.1 Sensing structure and principle

measurement [21], and biomedical parameter measurement

Schematics of the bare and the PDMS-coated in-line

couplers [16]-[17], [22], the dispersion turning phenomenon

microfiber MZI for RI and temperature sensing are shown in

has been observed, demonstrating that ultrahigh sensitivity

Fig. 1 (a) and Fig. 1 (b), respectively. The microfiber MZI

can be achieved when these microfiber sensors work around

which is fabricated by non-adiabatically tapering a single

the DTP. The DTP-based microfiber couplers have been

mode fiber is composed of two abrupt tapered regions and a

widely investigated for various applications like liquid RI

uniform waist region. When the fundamental HE11 mode is

measurement [16], liquid RI and temperature measurement

propagating through the first abrupt tapered region, only

in combination with temperature-sensitive material [17],

symmetrical high order modes (HE1m) can be excited owing

detection of cardiac troponin I [22]. The research of DTP-

to the symmetry of the abrupt tapered regions. Besides the

based microfiber MZI is not very extensive. In 2015, H. P.

fundamental HE11 mode, only the high order HE12 mode is

Luo et al. investigated the liquid RI sensing characteristic of

excited by the fabricated microfiber whose taper waist

the microfiber MZI [12]. In 2018, N. M. Y. Zhang et al.

diameter is 4.8 μm. The mode profiles of HE11 mode and

reported the gas RI and temperature sensing characteristic of

HE12 mode are shown in Fig. 1(c) and Fig. 1(d). These two

a tapered microfiber MZI operating around DTP [13]. The

modes interfere with each other at the second abrupt tapered

sensing characteristic of the microfiber MZI combined with

region, forming dual-path interference.

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[22], et al. For microfiber MZIs [12]-[13] and microfiber

optical-sensitive material working near DTP has not been

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studied.

The dual-path interference intensity I is expressed as:

In this work, we systematically and comprehensively studied the sensing characteristic of a microfiber MZI

I  I1  I 2  2 I1 I 2 cos 

(1)

Where I1 and I2 are intensities of HE11 mode and HE12

mode, and φ is the phase difference between these two

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operating near DTP, including the liquid RI and temperature

modes. When the following condition is satisfied, periodic

sensing characteristic of a bare microfiber, and the

interference dips are formed in the output spectrum.

temperature sensing characteristic of the microfiber MZI

N 

combined with polydimethylsiloxane (PDMS). An in-line microfiber MZI with taper waist of about 4.8 μm is

2

N

n eff L  (2 N  1)

(2)

N represents the wavelength of the Nth dip at

demonstrated to have high positive RI sensitivity around

interference spectrum, neff is the effective RI difference

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1.3320 and have high negative RI sensitivity around 1.405

between HE11 mode and HE12 mode.

in C + L band, indicating that this microfiber MZI works at

The RI sensitivity of N can be presented as [13]:

two sides of the DTP under low surrounding RI and high surrounding RI, respectively. An ultrahigh RI sensitivity of

SRI 

24209 nm/RIU (RI unit) around the RI of 1.3320 and an

( neff ) N ( neff ) N   HE11 N HE12  n ng  ng n G n

(3)

ultrahigh temperature sensitivity of 8.33 nm/℃ are obtained

G is the difference between the group effective RI of

by the bared microfiber MZI and the PDMS-coated

HE11 mode ngHE11 and that of HE12 mode ngHE12 . The group

microfiber MZI, respectively. The corresponding RI and

effective

temperature resolutions would be 8.26×10-7 RIU and 0.0024

3

RI

can

be

calculated

by ng  neff  N (neff ) / (N ) . We can conclude from Eq. (3) that the RI sensitivity of the microfiber MZI is related with wavelength N , G , and

( neff ) n

.

Fig. 2 (a) Calculated effective RI of HE11 ~ HE14 modes in the microfiber under different waist diameters of the microfiber at

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surrounding RI of 1.3320. (b) Calculated proportion of evanescent field (η) of the HE11 ~ HE14 modes under different taper waist diameters at surrounding RI of 1.3320. (c) Intensity distribution of

Schematic of PDMS-coated microfiber MZI for temperature

HE11 ~ HE14 modes when the taper waist diameter of the

sensing. (c) Mode profile of HE11 mode. (d) Mode profile of HE12

microfiber is 10 μm. (d) Intensity distribution of HE11 mode when

mode.

the taper waist diameter of the microfiber is varied from 0.6 μm to

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3.5 μm.

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Fig. 1 (a) Schematic of microfiber MZI for RI sensing. (b)

2.2 Simulation of sensing characteristics

According to Eq. (3), numerical calculation is carried

out to investigate the relationship between RI sensing

the sensing principle and performance of the microfiber

performance and taper waist diameter and wavelength. Fig.

MZI. Fig. 2(a) displays that the number of modes existing in

3(a) shows that when the taper waist diameter is increased

the microfiber increases as taper waist diameter increases

from the cut-off diameter to the taper waist diameter at the

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Numerical analysis is firstly conducted to investigate

dispersion turning point (i. e. G=0), G remains positive and

diameter is in the range of 3.2 μm ~ 5.8 μm. Fig. 2(b) shows

decreases rapidly towards zero. The corresponding RI

that the higher order mode has higher proportion of

sensitivity is calculated to be negative and decreases rapidly

evanescent field and the evanescent field decreases as the

in these narrow diameter range, as shown in Fig. 3(b). Fig.

taper waist diameter increases. Fig. 2(c) intuitively shows

3(a) and Fig. 3(b) also show that the cut-off diameter and

that light intensity of lower modes is more effectively

the dispersion turning diameter increase as surrounding RI

confined in the microfiber than the higher modes at the

increases.

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and only HE11 and HE12 modes exist when the taper waist

same taper waist diameter, implying that higher order modes are more sensitive than lower order modes. Fig. 2(d)

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intuitively shows that more light of the fundamental mode is confined in the microfiber as taper waist diameter raises, indicating that the evanescent field decreases with the increase of taper waist diameter.

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Fig. 3 (a) Calculated effective group index difference G and (b) RI

composed of two abrupt tapered regions (the region that the

sensitivity under different taper waist diameter when the

diameter of the optical fiber is varied between the taper

surrounding RI is from 1.3320 to 1.4053 and the incident

waist diameter and 125 μm, ~2 mm in length) and a uniform

wavelength is 1.55 μm. (c) Calculated effective group index

waist region (~6 mm in length and 4.8 μm in diameter).

difference G and (d) RI sensitivity under different incident wavelength when the surrounding RI is from 1.3320 to 1.4053 and the taper waist diameter is 4.8 μm.

Fig. 3(c) shows that when surrounding RI is in the range of 1.3320 ~1.3620, G of the microfiber MZI with the Fig. 4 Micrographs of the tapered microfiber. (a) The first abrupt

wavelength range of 1200 nm ~ 1800 nm, indicating that

tapered region. (b) The taper waist region. (c) The second abrupt

this microfiber MZI has a positive RI sensitivity. When

tapered region.

surrounding RI is 1.3920 and 1.4020, G keeps increasing

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taper waist diameter of 4.8 μm remains negative in the

3.2 Sensing characteristics of microfiber MZI

from a negative value to zero and then to a positive value

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Fig. 5(a) shows the interference spectrum of the

with the increasing of wavelength until reaching the HE12 mode cutoff wavelength.

fabricated microfiber MZI when surrounded by distilled

So the corresponding RI

water (whose RI is 1.3320 at wavelength of about 600 nm

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sensitivity increases from a positive value to positive

and temperature of 24 ℃ measured by using an Abbe

infinity from shorter wavelength to longer wavelength until

refractometer) and at room temperature. The sinusoidal

the DTP, as shown in Fig. 3(d). Then RI sensitivity

spectrum is generated by modal interference between HE11

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decreases from negative infinity at the DTP until reaching

mode and HE12 mode according to the above simulation

the cutoff wavelength, in which wavelength region the RI

analysis. The RI of liquid is increased by adding a few drops

sensitivity remains negative. It is clear that RI sensitivities

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of salt solution into the liquid to be measured. When the

are opposite at two sides of the DTP. At the C+L band

liquid mixes evenly owing to free diffusion after dozens of

which is roughly marked by the yellow rectangle in Fig.

minutes, the RI of the liquid is then measured by using an

3(d), the RI sensitivity is positive when surrounding RI is

Abbe refractometer at wavelength of about 600 nm and

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around the RI of water solution (the water solution is salt

solution with low concentration, whose RI is around 1.3320

temperature of 24℃, which is used as the calibration RI

at wavelength of about 600 nm and temperature of 24℃)

value. It should be mentioned that the material dispersion [23] of the liquid to be measured is ignored in this work

and the RI sensitivity is negative when surrounding RI is

because the RI of the liquid is measured by using an Abbe

around the RI of polydimethylsiloxane (PDMS, whose

refractometer which works at visible spectral region (at

material RI is about 1.405 at wavelength of about 600 nm

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wavelength of about 600 nm) whereas the optical fiber

and temperature of 24℃).

sensor works at near-infrared spectral region (at wavelength

3. Experiments and results

of around 1550 nm). This ignorance has little influence on

3.1 Fabrication of sensing structure

the measurement of RI sensing characteristic of the microfiber MZI because all RI values used as calibration in

Under the guidance of simulation, an in-line microfiber

the experiment are measured by the Abbe refractometer at

MZI supporting only HE11 and HE12 modes is fabricated by

visible spectral region. When surrounding RI increases, all

tapering a commercial single mode fiber. The micrograph of

the interference dips in Fig. 5(a) shift towards the longer

the fabricated microfiber MZI is shown in Fig. 4, which is

wavelength

5

direction,

causing

positive

RI

sensing

sensitivities. The RI sensitivities of dip a ~ dip d are 15305 nm/RIU, 15815 nm/RIU, 22072 nm/RIU, and 24209 nm/RIU. All the interference dips in the wavelength range of 1450 nm – 1700 nm have positive RI sensitivities when the surrounding RI is around 1.3320, and the interference dip at longer wavelength shows higher RI sensitivity than the

interference

dip

at

shorter

wavelength.

These

experimental results are consistent with the theoretical simulation results, as shown by the black line in Fig. 3(d). The difference between the RI sensitivities calculated in

of

simulation and achieved in experiment may be caused by the approximate calculation of the abrupt tapered region in

Fig. 5 (a) Interference spectrum of the microfiber MZI when the surrounding RI is 1.3320 at room temperature. The inset shows the

diameter, and the ignorance of material dispersion of the

variation of the interference spectrum as surrounding RI increases.

liquid to be measured. The inset of Fig. 5(a) shows the

(b) RI sensitivities of different interference dips of the microfiber

change of interference spectrum when surrounding RI

MZI. (c) Interference spectrum of the microfiber MZI when the

increases. The RI sensitivity of this microfiber MZI is

microfiber is in distilled water (RI is 1.3320) and the water

higher than that of our previous reported in-line photonic

temperature is 38 ℃ . The inset shows the variation of the

crystal fiber modal interferometer by two orders of

interference spectrum as temperature decreases. (d) Temperature

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simulation, the small error of the measured taper waist

sensitivities of different interference dips of the microfiber MZI.

magnitude [24]. When this microfiber MZI is put into

distilled water and the water is heated to 38 ℃ , its

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3.3 Sensing characteristics of the PDMS-coated microfiber MZI

interference spectrum is shown in Fig. 5(c). When the water

temperature naturally decreases, the interference spectrum

For further improving the temperature measurement

sensitivity,

inset of Fig. 5(c). The temperature sensitivities of Dip a’ ~

polydimethylsiloxane (PDMS), which has a material RI of

Dip g’ are shown in Fig. 5(d), displaying temperature

~1.405 at room temperature and a high thermo-optical

sensitivities ranging from -1.57 nm/℃ to -2.47 nm/℃. The

coefficient of −4.5×10−4/ ℃ . The microfiber MZI is

temperature response mainly results from the thermal-

packaged into the PDMS block, which has a length of about

optical effects of the microfiber and distilled water.

4 cm, width of about 2 cm, and thickness of about 3 mm. In

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shifts to the longer wavelength direction, as shown by the

the

microfiber

MZI

is

embedded

in

our opinion, the thickness of the PDMS has little influence

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the sensitivity of the PDMS-coated microfiber MZI as long as the thickness of the PDMS is much larger than the depth of the than evanescent because the temperature response of the PDMS-coated microfiber MZI is mainly determined by the structural parameters of the microfiber MZI and the thermal-optic effect of PDMS. The interference spectrum of the PDMS-coated microfiber MZI shifts to the shorter wavelength direction as temperature decreases, as shown in Fig. 6(a). It displays positive temperature sensitivities, as

6

shown by Fig. 6(b), which are 8.39 nm/℃, 8.28 nm/℃, and

an ultrahigh temperature sensitivity of about 8.33 nm/℃ is

8.33 nm/℃ for Dip a’’, Dip b’’, and Dip c’’, respectively.

achieved by the PDMS-coated microfiber MZI. This

The high temperature sensitivities of the PDMS-coated

ultrasensitive liquid RI sensor based on in-line microfiber

microfiber MZI mainly results from the thermo-optic effect

MZI has potential for measurement of relative humidity,

of PDMS. Because PDMS has a high material RI of about

biomedical and other liquid RI-related parameters owing to

1.405 and its material RI decreases as temperature rises, we

its advantages of ultrahigh sensitivity, very small size, and

can deduce that this microfiber MZI has a negative RI

little sample consumption.

sensitivity around the material RI of PDMS (about 1.405),

Conflict of interest Form

which is consistent with the simulation results. This PDMScoated microfiber MZI could achieve a temperature measurement resolution of about 0.0024 ℃ if the resolution

of

There is no Conflict of interest.

of the optical spectrum analyzer were 0.02 nm. The

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temperature response time of the PDMS-coated microfiber MZI is measured to be about 11s. This PDMS-coated

Acknowledgements

microfiber MZI with high temperature measurement

This work was supported in part by the National

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resolution is promising in applications like seawater

Natural Science Foundation of China under Grant 61425003

temperature monitoring and temperature monitoring in

and 61773102, the Fundamental Research Funds for the

biochemical reactions.

Universities

re

Central

under

Grant

N170406010,

N170407005, N160404002, N160408001, N150401001 and

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in part by the State Key Laboratory of Synthetical Automation for Process Industries under Grant 2013ZCX09.

References [1] Gu M Y, Yuan S, Yuan Q P, et al. Temperature-independent

ur na

Fig. 6 (a) Change of interference spectrum of the PDMS-coated

refractive index sensor based on fiber Bragg grating and spherical-

microfiber MZI when the water temperature is decreased from

shape structure[J]. Optics and Lasers in Engineering, 2019,

30.57 ℃ to 30.06 ℃ . (b) Temperature sensitivities of different

115:86-89.

interference dips of the PDMS-coated microfiber MZI.

[2] Zhao Y, Xia F, Hu H F, et al. A Ring-Core Optical Fiber

4. Conclusions

Sensor With Asymmetric LPG for Highly Sensitive Temperature Measurement[J]. IEEE Transactions on Instrumentation

In conclusion, we theoretically demonstrate that a

&

Jo

Measurement, 2017, 66(12):3378-3386.

microfiber taper MZI with taper waist of about 4.8 μm has a

[3] Zhao Y, Tong R J, Chen M Q, et al. Relative Humidity sensor

positive RI sensitivity when surrounding RI is around

based on Hollow Core Fiber Filled with GQDs-PVA[J]. Sensors

1.3320 and has a negative RI sensitivity when surrounding

and Actuators B:Chemical, 2019, 284:96-102.

RI is around 1.40 in the C + L band. We have

[4] Chen H, Shao Z, Zhang X, et al. Highly sensitive magnetic field sensor using tapered Mach–Zehnder interferometer[J]. Optics

experimentally demonstrated this by coating the microfiber

and Lasers in Engineering, 2018, 107:78-82.

MZI with PDMS and testing the temperature responses. As

[5] Zhao L, Zhang Y D, Wang J F, et al. Highly sensitive

a result, an ultrahigh RI sensitivity of 24209 nm/RIU at

temperature sensor based on an isopropanol-sealed optical

around 1.3320 is obtained by the bare microfiber MZI and

7

[16] Li K, Zhang T, Liu G, et al. Ultrasensitive optical microfiber

111901.

coupler based sensors operating near the turning point of effective

[6] Zhao Y, Peng Y, Chen M Q, et al. Humidity Sensor Based on

group index difference[J]. Applied Physics Letters, 2016,

Unsymmetrical U-shaped Microfiber with a Polyvinyl Alcohol

109(10):101101.

Overlay[J]. Sensors and Actuators B Chemical, 2018, 263:312-

[17] Li K, Zhang M, Zhang N, et al. Spectral Characteristics and

318.

Ultrahigh Sensitivities Near the Dispersion Turning Point of

[7] Ma Z, Miao Y, Li Y, et al. A Highly Sensitive Magnetic Field

Optical Microfiber Couplers[J]. Journal of Lightwave Technology,

Sensor Based on a Tapered Microfiber[J]. IEEE Photonics Journal,

2018, 36(12): 2409-2415.

2018, 10(4): 6803308.

[18] Le A D D, Han Y G. Relative Humidity Sensor Based on a

[8] Zhao Y, Tong R J, Xia F, et al. Current Status of Optical Fiber

Few-mode Microfiber Knot Resonator by Mitigating the Group

Biosensor based on Surface Plasmon Resonance[J]. Biosensors and

Index Difference of a Few-Mode Microfiber[J]. Journal of

Bioelectronics, 2019, 142:111505.

Lightwave Technology, 2018, 36(4): 904-909.

[9] Cai L, Zhao Y, Li X G. Applications of Modal Interferences in

[19] Gomes A D, Frazao O. Microfiber Knot with Taper

Optical

Interferometer

Fiber

Sensors

Based

on

Mismatch

Methods[J].

of

microfiber coupler[J]. Applied Physics Letters, 2018, 113(11):

for

temperature

and

refractive

index

discrimination[J]. IEEE Photonics Technology Letters, 2017,

[10] Liu Z, Liu L, Zhu Z, et al. Dual-channel surface plasmon

29(18): 1517-1520.

resonance refractive index sensor based on modified hetero-core

[20] Wang X, Wang J, Wang S S, et al. Fiber-Optic Salinity

structure fiber[J]. Optics Communications, 2017, 403:290-295.

Sensing

[11] Śmietana M, Dominik M, Mikulic P, et al. Refractive index

Interferometer[J]. Journal of Lightwave Technology, 2017,

sensing with Al2O3-nanocoated long-period gratings working at

35(23):5086-5091.

dispersion turning point[J]. Optics and Laser Technology, 2018,

[21] Luo H, Sun Q, Xu Z, et al. Microfiber-Based Inline Mach–

107:268-273.

Zehnder Interferometer for Dual-Parameter Measurement[J]. IEEE

ro

Instrumentation Science & Technology, 2015, 43(1):1-20.

a

Panda-Microfiber-Based

Multimode

re

-p

With

Photonics Journal, 2015, 7(2):1-8.

characteristics near the dispersion turning point of the multimode

[22] Zhou W, Li K, Wei Y, et al. Ultrasensitive label-free optical

microfiber-based Mach–Zehnder interferometer[J]. Optics Letters,

microfiber coupler biosensor for detection of cardiac troponin I

2015, 40(21):5042-5045.

based on interference turning point effect[J]. Biosensors and

lP

[12] Luo H, Sun Q, Li X, et al. Refractive index sensitivity

Bioelectronics, 2018, 106:99-104.

refractometers based on optical microfiber modal interferometers

[23] S. Kedenburg, M. Vieweg, T. Gissibl and H. Giessen, "Linear

operating at dispersion turning point[J]. Optics Express, 2018,

refractive index and absorption measurements of nonlinear optical

26(22): 29148-29158.

liquids in the visible and near-infrared spectral region," Optical

[14] Gao S, Sun L P, Li J, et al. High-sensitivity DNA biosensor

Materials Express, vol. 2, no. 11, pp. 1588-1611, 2012.

based on microfiber Sagnac interferometer[J]. Optics Express,

[24] Zhao Y, Li X G, Cai L, et al. Measurement of RI and

2017, 25(12):13305-13313.

Temperature Using Composite Interferometer With Hollow-Core

[15] Sun L P , Li J , Jin L , et al. High-birefringence microfiber

Fiber and Photonic Crystal Fiber[J]. IEEE Transactions on

Jo

ur na

[13] Zhang, NMY; Li, K; Zhang, N, et al. Highly sensitive gas

Sagnac interferometer based humidity sensor[J]. Sensors and

Instrumentation & Measurement, 2016, 65(11):2631-2636.

Actuators B: Chemical, 2016, 231:696-700.

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Biographies

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Yong Zhao received his M.A. and Ph.D. degrees, respectively, in precision instrument & automatic measurement with laser and fiber-optic techniques from the Harbin Institute of Technology, China, in 1998 and 2001. He was awarded a first prize scholarship in 2000 by the China Instrument and Control Society and the Sintered Metal Corporation (SMC) scholarship in Japan. He was a scholarship in Japan. He was a postdoctoral fellow in the Department of Electronic Engineering of Tsinghua University from 2001 to 2003, and then worked as an associate professor in the Department of Automation, Tsinghua University of China. In 2006, he was a visiting scholar of University of Illinois in Urbana and Champagne, USA. In 2008, he was awarded as the “New Century Excellent Talents in University” by the Ministry of Education of China. In 2009, he was awarded as the “Liaoning Bai-Qian-Wan Talents” by Liaoning Province. In 2011, he was awarded by the Royal Academy of Engineering as an academic research fellow of City University London. In 2014, he was awarded by the National Science Foundation for Distinguished Young Scholars of China. In 2015, he was honored as the Yangtze River Scholar Distinguished Professor by the Ministry of Education of China. Now he is working in Northeastern University as a full professor. As the academic leader and director of his research institute, his current research interests are the development of fiber-optic sensors and device, fiber Bragg grating sensors, novel sensor materials and principles, slow light and sensor technology, optical measurement technologies. He has authored and co-authored more than 260 scientific papers and conference presentations, 23 patents, and 5 books. He is a member in the Editorial Boards of the international journals of Sensor Letters, Instrumentation Science & Technology, Journal of Sensor Technology, and Advances in Optical Technologies.

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Feng Xia was born in Liaoning, China, in December 1992. She received her B.E. degree in measurement and instrumentation from College of Control Engineering, Northeastern University at Qinhuangdao, Hebei, China. She is currently working toward the PhD degree at College of Information Science and Engineering, Northeastern University, Shenyang, China. Currently her research interests are fiber-optic modal interference sensors, special fibers for generating orbital angular momentum mode and their sensing applications.

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Yun Peng was born in Hebei, China, in Jan. 1992. He received his B.A. degrees in the School of Mechanical Engineering from the Hebei University of Science and Technology, China, in 2015. He received his M.A. degrees in the School of Mechanical Engineering and Automation from the Northeastern University, China, in 2017. He is now a PhD student of Northeastern University. His research interests are optical microfiber sensors, optoelectronic measurement technology and system.

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