An Ultra-Sensitive Magnetic Field Sensor Based on ... - OSA Publishing

3332

JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 33, NO. 15, AUGUST 2015

An Ultra-Sensitive Magnetic Field Sensor Based on Extrinsic Fiber-Optic Fabry–Perot Interferometer and Terfenol-D Peng Zhang, Ming Tang, Senior Member, IEEE, Member, OSA, Feng Gao, Benpeng Zhu, Songnian Fu, Jun Ouyang, Zhiyong Zhao, Huifeng Wei, Jinyan Li, Perry Ping Shum, and Deming Liu

Abstract—We report a fiber-optic magnetic field sensor with ultra-high sensitivity based on a precisely configured extrinsic fiber-optic Fabry–Perot interferometer (EFFPI) and Terfenol-D slab. The EFFPI was simply formed by placing two well-cleaved single-mode fibers with carefully designed spacing and it was bonded to the surface of a Terfenol-D slab by epoxy resin. The experiments demonstrate good linear relationship between the applied magnetic field strength and the wavelength shift up to 560 Oe and the measurement range is only limited by the available bandwidth of the light source. The maximal sensitivity of the magnetic field measured by the proposed sensor is 854.73 pm/Oe through monitoring the shift of wavelength dip of the spectrum reflected from the EFFPI, which is significantly larger than most of the reported results. We also evaluated the repeatability of the proposed sensor and the performance of the proposed sensor working at a direct-current (dc)-biased magnetic field. Results indicated that the proposed fiber-optic magnetic field sensor exhibits good restorable measurement performance up to 140 Oe and a preapplied dc magnetic field can be used to extend the linear measurement dynamic range. Index Terms—Fabry–Perot interferometers, magnetic sensors, magnetostriction, optical fiber sensors.

Manuscript received December 24, 2014; revised May 21, 2015 and April 13, 2015; accepted May 22, 2015. Date of publication May 24, 2015; date of current version June 20, 2015. This work was supported in part by the 863 High Technology Plan of China (2013AA013402), the National Natural Science Foundation of China under Grant 61331010 and Grant 61107087, the Fundamental Research Funds for the Central Universities’, HUST: 2013TS052, and the Program for New Century Excellent Talents in University (NCET-130235). P. Zhang, M. Tang, F. Gao, S. Fu, Z. Zhao, and D. Liu are with the National Engineering Laboratory for Next Generation Internet Access System, School of Optics and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China (e-mail: hanbing@ hust.edu.cn; [email protected]; [email protected]; songnian@ mail.hust.edu.cn; [email protected]; [email protected]). B. Zhu and J. Ouyang are with the School of Optics and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China (e-mail: [email protected]; [email protected]). H. Wei is with the Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China, and also with the State Key Laboratory of Optical Fiber and Cable Manufacture Technology, Yangtze Optical Fiber and Cable Company Ltd. R&D Center, Wuhan 430073, China (e-mail: [email protected]). J. Li is with the Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China (e-mail: [email protected]). P. P. Shum is with the Centre for Optical Fibre Technology, School of Electrical and Electronic Engineering, Nanyang Technological University, 639798 Singapore, and also with 5CINTRA CNRS/NTU/Thales, 637553 Singapore (e-mail: [email protected]). Digital Object Identifier 10.1109/JLT.2015.2437615

I. INTRODUCTION HE magnetic field sensor can be widely used in the information storage, navigation, aerospace, military, and biomedical detection [1], etc. In the past few years, magnetooptical sensors have attracted great attention due to their unique advantages, such as small size, compact design, low cost, and immunity to electromagnetic interference as compared with their conventional competitors [2]. In principle, the fiberoptic system can detect magnetic field directly by measure the Faraday rotation of the light polarization [3]. Since no external transducer is required, this mechanism is ideal as an intrinsic sensor. However, its sensitivity is low due to the small Verdet constant of silica fibers. In order to employ fiber-optics to sense magnetic field and overcome the drawback of small magnetic sensitivity, the concept of fiber-optic strain sensor in conjunction with magnetostrictive material to detect tiny magnetic fields was first proposed in 1980 [4] and then achieved in 1983 [5]. In this kind of fiber-optic magnetic sensor, the magnetostrictive material functions as a magnetic actuator with magnetostrictive strain as the output, while the fiber-optic strain sensor operates as a strain sensor with the magnetostrictive strain from the magnetostrictive materials as the input [6]. Recently, Terfenol-D has become the most frequently-used giant magnetostrictive material as a magnetic actuator, strain sensitivity of which is greater than any other commercially available smart materials. Comparing with other magnetostrictive materials, it has many advantages, such as large magnetostrictive strain, large force, high coupling coefficient, rapid response, high energy density, and stable quality [7], etc. As for fiber-optic strain sensing, it has been focused on interferometric structure and fiber Bragg grating (FBG) due to their compactness, high sensitivity, ease of construction, and convenient operation [8]–[10]. The fiber magnetic field sensors based on fiber-optic strain sensor and Terfenol-D have been demonstrated [11]–[13]. However, the magnetic field measurement sensitivity of fiber magnetic field sensor based on Terfenol-D and FBG is only a fraction of a picometer per oersted, and it is so low that the sensor fails to meet the actual requirements of application. One of the most important reasons is that the strain sensitivity of magnetostriction materials resulting from an applied magnetic field in fiber-optic magnetic sensor is smaller than that of magnetostriction materials in a free state due to the elongation of silica fiber. It will greatly affect the performance of this kind of magnetic field sensing.

T

0733-8724 © 2015 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications standards/publications/rights/index.html for more information.

ZHANG et al.: ULTRA-SENSITIVE MAGNETIC FIELD SENSOR BASED ON EXTRINSIC FIBER-OPTIC FABRY–PEROT

Fig. 1.

Configuration of the proposed magnetic field sensor head.

In this paper, a fiber-optic magnetic sensor based on extrinsic fiber-optic Fabry–Perot interferometer (EFFPI) and magnetostrictive effect of Terfenol-D for static magnetic field measurement is presented and experimentally demonstrated. The EFFPI is simply fabricated by bonding two single mode fibers (SMFs) face to face with well-cleaved end face to the surface of a Terfenol-D slab. With the formation of two reflective mirrors of EFFPI, the change in Terfenol-D slab length resulting from an applied magnetic field is completely transferred to change in cavity length of EFFPI. Besides that, through the specific fixation method, the length change in Terfenol-D slab, whose length is far longer than the cavity length of EFFPI, will lead to enlarged change in the cavity length. All of this will greatly improve the performance of the magnetic sensor. The maximal sensitivity of magnetic field measurement we obtained is 854.73 pm/Oe that is three orders higher than that of the sensor based on Terfenol-D and FBG. Comparing with the EFFPI-based work reported in [11], [14], our work employs the SMF end face as the second reflecting mirror instead of magnetostriction materials rod end face, which ensure the light intensity reflected from the two mirrors are almost the same to achieve higher extinction ratio. In addition, this will greatly simplify the manufacture process and increase the stability of the proposed sensor. By interrogating wavelength shift of the optical spectrum reflected from the EFFPI, measurement of magnetic field strength has been accomplished. II. SENSOR FABRICATION AND OPERATION PRINCIPLE To implement the EFFPI, at first, two pieces of SMFs were well cleaved for getting smooth end face and higher reflectance. After that, two sections of SMFs were put on the surface of Terfenol-D slab face to face along the length of Terfenol-D slab and collimated by using a V-shaped groove. By doing so, the EFFPI is established with a small air gap between the fiber end faces, as shown in Fig. 1. In order to accurately adjust the cavity length of EFFPI steadily, one of two SMFs was fixed on Terfenol-D slab with V-shape groove by epoxy resin, and the other one was fixed on a micro-moving platform (Throlabs, lnc. with a resolution of 50 nm) by optical fiber fixture. During the process of adjusting cavity length of EFFPI, the light reflected from EFFPI was monitored by an optical spectrum analyzer (OSA) to acquire the cavity length information. Considering the bandwidth of the broadband source (BBS) and the operation wavelength of fiber-optic circulator (FOC), cavity length

3333

of EFFPI about 18 μm was chosen. When the cavity length reached 18 μm, the SMF fixed on micro-moving platform was then bonded on Terfeol-D by epoxy resin as soon as possible and the fixed point was kept away from V-shape groove, as shown in Fig. 1. So the longer effective retractable length L of Terfenol-D will be obtained. After the drying process of the epoxy resin, the final length of EFFPI cavity l and effective actuator length L we obtained is 18.306 μm and 10 mm, respectively. The proposed sensor is based on multi-beam interference theory of EFFPI and magnetostrictive effect of Terfenol-D slab. According to the Fresnel Reflection, the two mirrors’ reflection coefficients of EFFPI, as well as the interface between air and end face of SMF, can be expressed as n1 − n2 2 , (1) R= n1 + n2 where n1 is refractive index of the core of SMF, n2 is refractive index of air. The values of parameters used to estimate R are as follows: n1 is ∼1.45, and n2 is ∼1. According to Eq. (1), we have estimated the reflectance is about ∼3.37%. Due to low reflectivity at the fiber end face, the multiple reflection model of light of EFFPI can be derived with two-beam approximation and two beams of light reflected from the two fiber end faces have almost the same light intensities. In addition, two beams of reflected light have fixed phase difference. Hence, the reflectance spectrum with high extinction ratio will be obtained. Therefore, in this paper the reflecting direction is selected for spectrum measurement in order to get higher extinction ratio and it is also beneficial for sensing application. The spectrum reflected from EFFPI is affected by phase difference between beams reflected from two fiber end faces, respectively, ΔΦ = 4πl/λ0 ,

(2)

where λ0 is wavelength of the spectrum dip to be monitored, l is the cavity length of EFFPI. When the phase difference satisfies ΔΦ = 2mπ, where m is integral, the reflective spectrum reaches its minimal intensity, and the dip wavelength is determined by: λ0 = 2l/m.

(3)

When the cavity length is perturbed, the spectral shift, Δλ, is given by [9]: Δl , (4) l where Δl is the change in cavity length. When Terfenol-D slab is stretched by external stimulus of magnetic field, the cavity length of EFFPI gluing to it will be also elongated [1]. With the mechanical structure proposed in our method, the change of F-P cavity length Δl is equal to that of Terfenol-D slab length ΔL, i.e., Δl = ΔL. So, the sensitivity of magnetic measurement can be expressed by: Δλ = λ0

Δλ λ0 ΔL = , (5) ΔH l ΔH where ΔH is the change in magnetic effect corresponding to the change in Terfenol-D slab length ΔL. For the magnetostrictive material, the strain is a quantity that only varies with the

3334


Fig. 2. Schematic diagram of the experimental setup. BBS stands for broadband optical source; OSA stands for optical spectrum analyzer; FOC stands for fiber optic circulator.

magnetic field. On the contrary, the change of the effective slab length depends not only on the magnetic field strength but also on the effective retractable length of the Terfenol-D L. So rewriting the Eq. (5), we can obtain that: Δλ L Δε = λ0 , ΔH l ΔH

(6)

where Δε is the strain change in Terfenol-D slab. It is obvious that the sensitivity of magnetic field measurement of the proposed sensor increases with the increasing detected wavelength λ0 and the ratio between the L and l. Choosing the smaller l and larger L, the magnetic field measurement sensitivity can be greatly magnified. According to the value getting from the sensor, the magnetic field sensitivity of sensor is magnified 546 times by this specific configuration of sensor comparing to the situation that L is equal to l. III. EXPERIMENTAL RESULTS AND DISCUSSIONS Fig. 2 shows the experimental setup for evaluating the static performances of the magnetic sensor. To analyze the performance and sensing properties of the proposed sensor, we launched light to the EFFPI from a BBS through a FOC, and the reflective light was fed to an OSA. The proposed sensor was situated between two water-cooled electromagnets (fabricated by East Changing Technologies, Inc.) to receive the stimulus of magnetic fields in the longitudinal direction of the sensor (also along the length direction of the Terfenol-D bar). The reflection spectrum of the proposed sensor was recorded under magnetic field intensity increasing from 0 to 500 Oe with a step of 4 Oe, from 500 to 800 Oe with a step of 10 Oe, and from 800 to 900 Oe with a step of 20 Oe, as shown in Fig. 3. Due to the limited bandwidth of BBS and the large free spectral range (FSR) of spectrum reflected from the sensor (due to the small cavity length of EFFPI), a specific dip will shift out of the bandwidth of BBS with increasing magnetic field, subsequently lose the ability to sense magnetic field. In order to establish direct correspondence between the dip wavelength and magnetic field and avoid the situation that two different magnetic fields correspond to the same dip wavelength, the dip with shorter wavelength on spectrum is assigned to sense magnetic field and the spectrum can be divided into eight portions as shown in Fig. 3(a)–(h). From the Fig. 3, we can clearly see that the reflective spectrum shift to the longer wavelength with the increasing magnetic field. When the proposed sensor was exposed in external magnetic field, Terfenol-D slab and cavity

Fig. 3. Spectrum reflected from the proposed sensor under magnetic field from (a) 0 to 208 Oe, (b) 124 to 228 Oe, (c) 228 to 300 Oe, (d) 304 to 372 Oe, (e) 376 to 460 Oe, (f) 464 to 560 Oe, (g) 570 to 700 Oe, and (h) 710 to 900 Oe.

length of EFFPI gluing to it will be stretched. According to Eq. (4), the dip wavelength will be larger than the original. From the recorded spectra reflected from the sensor head, as shown in Fig. 3, we get the relationship between dip wavelength and magnetic field strength as shown in Fig. 4. It is obvious that, at first, the relationship between dip wavelength and magnetic field strength is nonlinear, as shown in Fig. 4(a) and (b). Next, it becomes linear gradually, as shown in Fig. 4(c)–(f). At last, it becomes nonlinear again, as shown in Fig. 4(g) and (h), with the increasing magnetic field strength. Through the result of linear fitting, one also can see that the sensitivity of magnetic field measurement increases firstly and then decreases with the increase of magnetic field strength. And the maximal sensitivity of the proposed sensor about 854.73 pm/Oe is obtained in the range from 232 to 300 Oe, as shown in Fig. 4(c). According to the relationship between strain in Trefenol-D and applied magnetic field [15], Δε/ΔH increases firstly and then decreases with the increase of magnetic field strength. Consequently, the magnetic measurement sensitivity will increases firstly and then decrease


3335

Fig. 5. The repeatability test of the proposed sensor when the magnetic field is smaller than 140 Oe.

Fig. 4. The shift of the resonance wavelength as magnetic field strength increasing from (a) 0 to 208 Oe, (b) 124 to 228 Oe, (c) 228 to 300 Oe, (d) 304 to 372 Oe, (e) 376 to 460 Oe, (f) 464 to 560 Oe, (g) 570 to 700 Oe, and (h) 710 to 900 Oe.

with the applied magnetic field increasing, according to the Eq. (6). For different magnetic field strength range, the reflection spectra are similar and it becomes difficult to distinguish them and choose the right slope. Fortunately, for different magnetic field strength range, the length of Terfenol-D and cavity length of EFFPI are different. So, the FSR of reflectance spectrum is different. According to the value of FSR, we can distinguish the reflection spectra under different magnetic field strength range and choose the right slope. We can further create a table which shows corresponding relationship between slope and magnetic field range to conveniently choose the slope value and calibrate the measured magnetic field. The repeatability of the proposed sensor was also tested. When one measurement was finished and magnetic field decreased to 0 Oe, we carry out the repeatability test immediately. When the last applied maximal magnetic field is smaller than 140 Oe, the dip wavelength will go back to the original location if the magnetic field reduces to 0 Oe. The result of two different

measurements is shown in Fig. 5. From the Fig. 5, it is clear that the effect of hysteresis on the location of dip wavelength under different magnetic field can be ignored. So, we can directly measure the magnetic field through the location of dip wavelength. Obviously, it is convenient to measure the magnetic field employing the linear relationship between dip wavelength and magnetic field. However, the range of linear relationship between dip wavelength and magnetic field is from 232 to 460 Oe. And when the maximal magnetic field experienced is larger than 140 Oe, the dip wavelength cannot return to the original dip wavelength due to the hysteresis in Trefenol-D even if the magnetic field decreased to 0 Oe. In this case, we cannot build direct relationships between the magnetic field and the absolute dip wavelength. Fortunately, the relative shift of dip wavelength can be used to measure magnetic field. Since the linear relationship between dip wavelength shift and magnetic field is indispensable to magnetic sensing, we focus on the magnetic field range from 232 to 460 Oe. The sensitivity of the proposed sensor under magnetic field from 232 to 460 Oe is shown in Fig. 6 for a second measurement. Comparing results shown in the Figs. 4 and 6, we can see that the sensitivity of sensor and the standard error of linear fitting at the same magnetic field range are identical within the measurement uncertainties, except for the absolute dip wavelength. Considering results of two different measurements, it is possible that we can measure the magnetic field by biasing the sensor with a direct current (dc) biased magnetic field and measuring the shift of dip wavelength rather than the location of absolute dip wavelength and this measuring method can overcome the hysteresis of Terfenol-D slab. In order to evaluate the performance of magnetic field measurement through measuring the value of dip wavelength shift, firstly, the magnetic field around the sensor head was directly increased to the dc bias magnetic field of 300 Oe from zero magnetic field quickly, then increased to 376 Oe with a step of 4 Oe. The relationship between the relative shift of dip wavelength and the magnetic field added from 300 Oe offset is shown in Fig. 7. The obtained sensitivity is almost the same with the results showing in Figs. 4(d) and 6(b). So it is clear that we can measure the magnetic field using the relative shift of dip wavelength through biasing the sensor with a dc bias magnetic field and the hysteresis of Terfenol-D slab can be ignored. The reason can be explained as follows. Due to the hysteresis of

3336


IV. CONCLUSION Highly sensitive magnetic field sensors based on Terfenol-D and EFFPI have been proposed and demonstrated in this paper. Through separation of two fiber end-face mirrors of EFFPI, by combining the longer elastic length of Terfenol-D and the smaller cavity length of EFFPI, the sensitivity of the proposed sensor has been improved enormously. The magnetic field sensitivity of the sensor is as large as 854.73 pm/Oe. We also tested the repeatability of the sensor and two different kinds of working scenarios are demonstrated. When the maximal magnetic field is lower than 140 Oe, the proposed sensor can ignore the hysteresis of Terfenol-D and measure the magnetic field directly by tracing the location of absolute dip wavelength. The proposed sensor also can operate at a linear model to obtain the magnetic field through measuring the relative shift of dip wavelength and overcome the hysteresis of Terfenol-D. In future, the sensitivity of sensor can be further improved by reducing the cavity length of EFFPI and increasing the effective retractable length of Terfenol-D. REFERENCES

Fig. 6. The relationship between the dip wavelength and magnetic field for the second measurement under different magnetic field range.

Fig. 7. The sensitivity of the proposed sensor with a dc biased offset magnetic field of 300 Oe.

Terfenol-D slab, the induced strain of Terfenol-D slab can be different even under the same magnetic field strength. However, the slope Δε/ΔH remains almost identical provided the applied magnetic field strength is located in the linear range of strain-magnetic field strength map [15]. So according to the Eq. (6), the magnetic fields obtained by measuring shift of dip wavelength are almost the same, though Terfenol-D slab does have significant hysteresis. If choosing dc bias magnetic field of 230 Oe, we will get the largest magnetic field measurement sensitivity ∼854.73 pm/Oe according to the Figs. 4(c) and 6(a).

[1] J. Lenz and A. S. Edelstein, “Magnetic sensors and their applications,” IEEE Sens. J., vol. 6, no. 3, pp. 631–649, Jun. 2006. [2] D. Davinoa, C. Visone, C. Ambrosino, S. Campopiano, A. Cusano, and A. Cutolo, “Compensation of hysteresis in magnetic field sensors employing fiber Bragg grating and magneto-elastic materials,” Sens. Actuators A Phys., vol. 147, no. 1, pp. 127–136, Sep. 2008. [3] L. Sun, S. Jiang, and J. R. Marciante, “All-fiber optical magnetic-field sensor based on Faraday rotation in highly terbium-doped fiber,” Opt. Exp., vol. 18, no. 6, pp. 5407–5412, Mar. 2010. [4] A. Yariv and H. V. Winsor, “Proposal for detection of magnetic fields through magnetostrictive perturbation of optical fiber,” Opt. Lett., vol. 5, no. 3, pp. 87–89, Mar. 1980. [5] J. P. Willson and R. E. Jones, “Magnetostrictive fiber-optic sensor system for detecting dc magnetic fields,” Opt. Lett., vol. 8, no. 6, pp. 333–335, Jun. 1983. [6] H. L. Liu, S. W. Or, and H. Y. Tam, “Magnetostrictive composite-fiber Bragg grating (MC-FBG) magnetic field sensor,” Sens. Actuators A Phys., vol. 173, no. 1, pp. 122–126, Jan. 2012. [7] G. Engdahl, Ed., Handbook of Giant Magnetostrictive Materials. New York, NY, USA: Academic, 2000. [8] J. T. Zhou, Y. P. Wang, C. R. Liao, G. L. Yin, X. Xu, K. M. Yang, X. Y. Zhong, Q. Wang, and Z. Y. Li, “Intensity-modulated strain sensor based on fiber in-line Mach–Zehnder interferometer,” IEEE Photon. Technol. Lett., vol. 26, no. 5, pp. 508–511, Mar. 2014. [9] Q. Shi, F. Y. Lv, Z. Wang, L. Jin, J. J. Hu, Z. Y. Liu, G. Y. Kai, and X. Y. Dong, “Environmentally stable Fabry–P´erot-type strain sensor based on hollow-core photonic bandgap fiber,” IEEE Photon. Technol. Lett., vol. 20, no. 4, pp. 237–239, Feb. 2008. [10] N. Kuse, A. Ozawa, and Y. Kobayashi, “Static FBG strain sensor with high resolution and large dynamic range by dual-comb spectroscopy,” Opt. Exp., vol. 21, no. 9, pp. 11141–11149, May 2013. [11] K. D. Oh, A. Wang, and R. O. Claus, “Fiber-optic extrinsic Fabry–Perot dc magnetic field sensor,” Opt. Lett., vol. 29, no. 18, pp. 2115–2117, Sep. 2004. [12] G.N. Smith, T. Allsop, K. Kalli, C. Koutsides, R. Neal, K. Sugden, P. Culverhouse, and I. Bennion, “Characterisation and performance of a TerfenolD coated femtosecond laser inscribed optical fibre Bragg sensor with a laser ablated microslot for the detection of static magnetic fields,” Opt. Exp., vol. 19, no. 1, pp. 363–370, Jan. 2011. [13] Y. T. Dai, M. H. Yang, G. Xu, and Y. Q. Yuan, “Magnetic field sensor based on fiber Bragg grating with a spiral microgroove ablated by femtosecond laser,” Opt. Exp., vol. 21, no. 14, pp. 17386–17391, Jul. 2013. [14] K. D. Oh, J. Ranade, V. Arya, A. Wang, and R. O. Claus, “Optical fiber Fabry–Perot interferometric sensor for magnetic field measurement,” IEEE Photon. Technol. Lett., vol. 9, no. 6, pp. 797–799, Jun. 1997. [15] D. Satpathi, J. A. Moore, and M. G. Ennis, “Design of a terfenol-D based fiber-optic current transducer,” IEEE Sens. J., vol. 5, no. 5, pp. 1057–1065, Oct. 2005.


Peng Zhang was born in Hubei Province, China, in 1987. He received the B.S. degree in physics from the Jianghan University of Science and Technology, Wuhan, China, in 2011. He is currently working toward the Ph.D. degree under the Professor M. Tang within the National Engineering Laboratory for Next Generation Internet Access System and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan. His research interests include optical fiber sensor and devices.

Feng Gao, biography not available at the time of publication.

Benpeng Zhu, biography not available at the time of publication.

Songnian Fu, biography not available at the time of publication.

Jun Ouyang, biography not available at the time of publication.

Ming Tang (SM’11) received the B.Eng. degree from the Huazhong University of Science and Technology (HUST), Wuhan, China, in 2001, and the Ph.D. degree from Nanyang Technological University, Singapore, in 2005. He was a Postdoctoral Researcher with the Network Technology Research Centre, where his research interests include the optical fiber amplifiers, high-power fiber lasers, nonlinear fiber optics, and all-optical signal processing. From February 2009, he was with Tera-photonics group led by Prof. H. Ito in RIKEN, Sendai, Japan, as a Research Scientist conducting research on terahertz-wave generation, detection, and application using nonlinear optical technologies. Since March 2011, he has been a Professor at the School of Optical and Electronic Information, Wuhan National Laboratory for Optoelectronics, HUST. He has published more than 100 technical papers in the international recognized journals and conferences. His current research interests include optical-fiber-based linear and nonlinear effects for communication and sensing applications. He has been a Member of the IEEE Photonics Society since 2001 and also a Member of the OSA.

Zhiyong Zhao, biography not available at the time of publication.

Huifeng Wei, biography not available at the time of publication.

Jinyan Li, biography not available at the time of publication.

Perry Ping Shum, biography not available at the time of publication.

Deming Liu, biography not available at the time of publication.

3337