JOURNAL OF ELECTRONIC SCIENCE AND TECHNOLOGY, VOL. 13, NO. 4, DECEMBER 2015

291

AbstractAs mid-infrared (MIR) lasers show numerous applications in the field of defense, medical, materials processing, and optical communications. Investigation on MIR Raman fiber lasers (RFLs) increasingly becomes a hot topic. Compared with the traditional silica fibers, fluoride and chalcogenide glass fibers possess higher nonlinear coefficients and excellent MIR transmittances. In this article, the latest developments of the MIR RFLs using fluoride and chalcogenide glass fibers as gain media are introduced, respectively. This review article mainly focuses on the developments of MIR RFLs in aspects of output wavelength, output power, and optical efficiency. Besides, the prospect of MIR RFLs is also discussed.

Index TermsChalcogenide fiber, fluoride fiber, mid-infrared, Raman fiber laser.

1. Introduction

The Raman fiber laser (RFL) is an important application of stimulated Raman scattering (SRS). It refers to a specific type of fiber laser that uses SRS, instead of stimulated electronic transitions, to amplify light. Among different types of RFLs, rare earth ions doped RFLs are of most importance and grow rapidly. In comparison with conventional chemical and solid-state lasers, RFLs have the advantages of high conversion efficiency, compactness, excellent beam quality, and great heat dissipation. Moreover, based on the principle of SRS, applying pump sources with different wavelengths can lead to outputs with longer Stokes wavelength and wider tunable wavelength range.

Near-infrared (1 μm to 2 μm) RFLs have been developed for years, the gain media are mainly oxide fibers such as silica fiber, phosphosilicate fiber, and germane silicate fiber. A cascaded RFL with output power of up to 301 W at 1480 nm has been reported[1]. This is also the

Manuscript received July 15, 2015; revised September 14, 2015. This

work was supported by the Fundamental Research Funds for the Central Universities under Grant No. ZYGX2015KYQD015.

H. Zhang is with Douglas Scientific LLC, Alexandria, MN 56308, USA (Corresponding e-mail: han.zhang@ douglasscientific.com).

C. Liu, C. Wei, and Y. Liu are with the School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054, China (e-mail: liucong2666@163.com; cwei@uestc. edu.cn; yongliu@uestc.edu.cn).

Digital Object Identifier: 10.11989/JEST.1674-862X.508062

RFL with the highest output power at 1.5 μm. The Shanghai Institute of Optics has demonstrated a RFL yielding 300 W at 1120 nm by using a new type of Yb3+-integrated Raman fiber amplifier[2]. Subsequently, with further system optimization, they successfully increased the output power by an order of magnitude to 1.3 kW[2]. Recently, National University of Defense Technology has built a RFL at 1090 nm by utilizing six cascading fiber lasers at 1018 nm to pump Yb3+-doped silica fiber. Eventually, the maximum output power of 2.14 kW has been obtained[3].

Mid-infrared (MIR) lasers with output wavelength of over 2 μm have wide spread and important applications in the fields of communication, national defense, biomedical science, and so on[4]. For instance, this kind of laser can be used in laser radar, laser ranging, and air communication as a result of the atmosphere transparent window ranging from 3 μm to 5 μm. Moreover, it locates in the operation band of most military detectors and is widely applied in many military fields including laser guidance, telemetry, and optical-electronic countermeasures. Additionally, since water molecules have a strong absorption peak at 2.94 μm wavelength, it can also be used in laser surgery exhibiting the advantages of rapid blood coagulation, small surgical wounds, and excellent hemostatic effects[5]. Traditional oxide fibers, especially silica fibers, are not suitable for MIR RFLs since they have a high transmission loss for the wavelength beyond 2 μm as a result of their high phonon energy. In order to obtain MIR wavelength output exceeding 2 μm, fibers with low phonon energy and small transmission loss in MIR band are required. Currently, fluoride and chalcogenide fibers are the most common gain media in MIR RFLs because of their excellent performances at that wavelength[6],[7].

This article introduces current research on MIR RFLs based on fluoride and chalcogenide fibers, respectively. The performances of both MIR RFLs have been compared and analyzed. In the end, the prospect of future development of MIR RFLs is discussed.

2. Theoretical Outline In a RFL, the Raman gain coefficient (gR) is a basic

parameter to describe the Raman scattering. It can be obtained by experimental measurement. The Raman on-off gain (G) is defined as the ratio of the output powers when the pump power is on and off[8]:

Mid-Infrared Raman Fiber Lasers

Cong Liu, Han Zhang, Chen Wei, and Yong Liu

29

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As-Se fibers aAs-S fibers[10]

luoride and chRaman laser ou

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where p is thwavelength, ant is a second-o

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3. D

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Bragg grating MIR RFLs to uccessfully inemtosecond laluoride fiber hhown in Fig. erved as the

maximum CW ilica fiber lasiode array froelivering a mnto a 29 m lon

expG

the input puh, and Aeff iscan be calculaman gain coeof silica fiberoefficient 50 e fibers (20×1and 4.357×10–

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DevelopmRaman

common fluormol.% ZrF4, and 20 mol.%

mission windy, rare earth iofiber lasers c

gth[13]–[16]. Ho(FBG) hindesome extent

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W power of 96 ser was pumpom QPC Laseaximum powe

ng fluoride fib

eff0

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h Raman gaiibers make it

hort gain fibersic pump wavebe theoretical

1 s

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wavelength of ogenide fibers

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JOURNAL OF E

Leff is the fective modeasuring the ouoride fibers igenide fibers

times higher51×10–12 m/W

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e first order Stthe second-o

bers is about e fibers (240

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BLAN fiber waF2, 4 mol.%ZBLAN fiber

from 0.35 μTm3+, Ho3+, oroutput with 2 μlack of MIRer developmethe FBG has r using an 80RFL based o

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which providm. The Tm3+-dightLase Ultrting at 792 nm

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ELECTRONIC SC

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sum up, thougL was obtainciencies were

HR FB

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TECHNOLOGY, V

al setup of 2185

meter and num6.5 μm and 0ed in both ended at 100 °C

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Numerical sim(constant Rou

▲ Experimental measurements

VOL. 13, NO. 4,

5 nm RFL[11].

merical apert.23 μm, respeds of the fiberC for 5 minuFig. 2 shows nched pump p

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792 nm lasdiode pum

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DECEMBER 20

ture (NA) of ctively. A pair

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inly consist oa Ge, As, Sb, aAs-S fibers, Aission window10 μm for Asthe Raman amm[19]. S. D. Jautput power oTm3+-doped siber[20].

MIR fiber laserRFLs with th

al. have emplolse laser anGs in the lowthen firstly wavelength o

n in Fig. 7. si-continuous μm as the pu

nd L2) were u

2S3 single-modof 0.36, a core

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ectra of the pwith that o

s significantly

JOURNAL OF E

o-optical efficp has been obtvity. In practic1981 nm pump

alcogenidLaser

of chalcogensand other elem

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rs over 3 μmhe longer St

oyed a home-mnd phase m

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wave Er3+-dump source, aused to couplde fiber whichdiameter of 4

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the original pW, the actual poss included

w pass filter (Lent light and A

.

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broadened.

ELECTRONIC SC

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CIENCE AND T

8. Spectra of th

Fig. 9 shows kes peak pownched pump aput powers incximum averag.6 W were ob

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3.34 μm andwer increased,

3.002 3.00

0

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50

40

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20

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mW

)

TECHNOLOGY, V

he pump, FBGs

the Stokes avwer (y-axis raverage powercrease linearly

ge output powetained with a

ser threshold w

rage power anump power[22].

M. Bernier escaded RFL s wavelength wo the record emperature[23]

yed the samide fiber lase

same self-c. It was estimcascaded Ramp power, the 00% couplings a piece of 2.eters as that uGs directly in

ed as the laser of the outpup light and thews the spectrand second-ordfirst-order andd 3.766 μm, the spectrum

Pump spectrum

Pump HR

04 3.006 Wavelen

100 150 unched pump avera

VOL. 13, NO. 4,

s, and Stokes[22]

verage power (right) as a fr. It can be oby with the puer of 47 mW aslope efficien

was 125 mW.

nd peak power

et al. have dbased on thwas further exwavelength f. The experim

me quasi-coner at 3.005 μmollimation mmated that thman cavity wmaximum pu

g efficiency a.8 m As2S3 sin

used in the abonscribed in thser cavities out end was us

e first-order Sta of pump lader Stokes lad second-ordrespectively.

m of first-ord

Stokesspectrum

StokesHR

S

3.338 ngth (m)

200 250 age power (mW)

=39%

DECEMBER 20

.

(y-axis left) anfunction of tbserved that tump power. Tand peak pow

ncy of 39%. T

as a function

demonstrated he chalcogenixtended to 3.7from MIR fibmental setup

ntinuous wam as the pum

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300

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frared Raman Fib

broadened whme. Fig. 12 sk power of thee average pumcoupler (OC) avely. It can bslope efficienthe OC. The

and 8.3%, res

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m: (a) pump spctrum[23].

-order Stokes average pump p

Er

Er3+-doped FGL=5.2 m

: P

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980 nm pump diodes

Low power spec

Input coupler (IC

3.002 3

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Rout

=

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hile that of seshows the ave second-ordemp power what 3.77 μm w

be observed thncy increase wcalculated slospectively. W

3.77 μm cascad

pectrum, (b) Sto

average power aower[23].

r3+: FG pump fiber l

G fiber,

Pump at 3.005 m

01 m O

trum Hig

C) Ou(a) Pump

(b) Stokes 1

(c) Stokes 2

.004 3.006 3

3.765 3.7Wavelength (m)

5 3.34 3

d pump power (mW00 350 400

t=80% 8.3%

Rout=92=3.5%

Rout=98=1.1%

econd-order Stverage powerer Stokes laserhen the reflectas 98%, 92%hat both the with the increope efficiency

When the OC

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okes 1 spectrum

and peak power

laser

OC at 3.01 m

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utput coupler (OC)

3.008 3.01

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at

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OC at 3.77 μm158 mW wituired. Howeveesult of accieriencing the c

The obtainedkes wavelengign research.

wer and sloperoved by thesed by FBGsrage loss wadening of the

We have briefR RFLs. Theched hundredskes wavelenlcogenide RFLh longer waveride RFLs h

velength of 2lcogenide RFLh a longer mpared witharch in the e[24]–[28]. Thoum have been aining. In ociency operaties of efforts snonlinear MIRfiber passiveend the output

Cto RFL

L2

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IC at 3.34

As2S3Ch

was utilized, t9 mW corresbtained at th

numerical stimm was reduced

th a slope eer, it cannot bidentally noncycle process

d wavelength gth in RFLs

Above resule efficiency e following s (every FBG

was 3% to e first-order St

5. Con

fly introducedrare earth io

s of watts orngth less thLs have yieldlength beyondhave reachedμm to 3 μm.Ls is relativelStokes wavethe research

MIR RFLsugh some prog

achieved, theorder to realion of RFLs ashould be depR fiber, fabri

componentswavelength o

Cascaded chalcogen

: Stokes 2 at 3

4 mIC at 3.77

OC at 3.

hG fiber, L=2.8 m

the maximum ponding to a e launched p

mulation, whento 60%, a peafficiency of be realized exnlinear fiber of thermal an

of 3.766 μmfrom domes

ts present thewere very laspects: RedG has been 4%), suppre

tokes light, an

nclusions

d the recent dons doped oxr even kilowhan 2 μm. ded the Ramad 2 μm. The od watt-level The output ly low at mil

elength of ulevel abroad

s is still at gresses on MIRere are still mlize high poat longer MIRployed to impricate high-pers, increase thof the pump so

nide RFL

3.766 m

m

OC at 3.34 m

.77 m

F2

2

Stokes averapeak power

pump powern the reflectiviak output pow12% could

xperimentally damage wh

nnealing.

m is the longestic research e Stokes outplow, it can ducing the lo

tested and tessing spectr

nd so on.

evelopments oxide RFLs hawatts level wi

Fluoride anan laser outpuoutput powers

with emissiopower level

lliwatt level bup to 3.77 µmd, the domest

a preliminaR RFLs beyon

many challengower and hig

R wavelengthsrove the qualirformance MIhe power, anource, etc.

295

age of of ity

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oss the ral

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JOURNAL OF ELECTRONIC SCIENCE AND TECHNOLOGY, VOL. 13, NO. 4, DECEMBER 2015

296

References

[1] V. R. Supradeepa and J. W. Nicholson, “Power scaling of high-efficiency 1.5 μm cascaded Raman fiber lasers,” Optics Letters, vol. 38, no. 14, pp. 2538 2541, 2013.

[2] L. Zhang, C. Liu, H. Jiang, Y. Qi, B. He, J. Zhou, and Y. Feng, “1.3 kW Raman fiber laser,” Chinese Journal of Lasers, vol. 6, pp. 22 22, Mar. 2014 (in Chinese).

[3] H. Xiao, J. Leng, H. Zhang, L. Huang, S. Guo, P. Zhou, and J. Chen, “2.14 kW cascade-pumped Raman fiber amplifier,” High Power Laser and Particle Beams, vol. 27, no. 1, pp. 010103-1–0.0103-2, 2015 (in Chinese).

[4] J. S. Sanghera, L. B. Shaw, L.E. Busse, et al., “Infrared optical fibers and their applications,” in Proc. 1999 SPIE Conf., Boston, 1999, pp. 38 49.

[5] M. Pollnau and S. D. Jackson, Advances in Mid-Infrared Fiber Lasers, Berlin: Springer, 2008, pp. 315 346.

[6] P. W. France, M. G. Drexhage, and J. M. Parker, Fluoride Glass Optical Fibers, Glasgow: Blackie, 1990, ch. 1.

[7] L. B. Shaw, B. Cole, P. A. Thielen, J. S. Sanghera, and L. D. Aggarwal, “Mid-wave IR and long-wave IR laser potential of rare-earth doped chalcogenide glass fiber,” IEEE Journal of Quantum Electronics, vol. 48, no. 9, pp. 1127 1137, 2001.

[8] G. P. Agrawal, Nonlinear Fiber Optics, 5th ed. Oxford, U.K: Academic Press, 2013, ch. 8, pp. 299.

[9] V. Fortin, M. Bernier, J. Carrier, and R. Vallee, “Fluoride glass Raman fiber laser at 2185 nm,” Optics Letters, vol. 36, no. 21, pp. 4152 4154, 2011.

[10] R. T. White and T. M. Monro, “Cascaded Raman shifting of high-peak-power nanosecond pulses in As2S3 and As2Se3 optical fibers,” Optics Letter, vol. 36, no. 12, pp. 2351 2353, 2011.

[11] T. Mizunami, H. Iwashita, and K. Takagi, “Gain saturation characteristics of Raman amplification in silica and fluoride glass optical fibers,” Optics Communications, vol. 97, no. 1−2, pp. 74 78, 1993.

[12] J. S. Sanghera, L. Shaw, P. Pureza, et al., “Nonlinear properties of chalcogenide glass fiber,” Intl. Journal of Applied Glass Science, vol. 1, no. 3, pp. 296 308, 2010.

[13] Y. D. Huang, M. Mortier, and F. Auzel, “Stark level analysis for Er3+-doped ZBLAN glass,” Optical Materials, vol. 17, no. 4, pp. 501 511, 2001.

[14] S. D. Jackson, “Single-transverse-mode 2.5 W holmium- doped fluoride fiber laser operating at 2.86 μm,” Optics Letters, vol. 29, no. 4, pp. 334 336, 2004.

[15] D. Faucher, M. Bernier, N. Caron, and R. Vallee, “Erbium-doped all-fiber laser at 2.94 μm,” Optics Letters, vol. 34, no. 21, pp. 3313 3315, 2009.

[16] S. D. Jackson, “High-power and highly efficient diode- cladding-pumped holmium-doped fluoride fiber laser operating at 2.94 μm,” Optics Letters, vol. 34, no. 15, pp. 2327 2329, 2009.

[17] M. Bemier, D. Faucher, R.Vallee, A. Saliminia, G. Androz, Y. Sheng, and S. L. Chin, “Bragg gratings photoinduced in ZBLAN fibers by femtosecond pulses at 800 nm,” Optics

Letters, vol. 32, no. 5, pp. 454 456, 2007. [18] V. Fortin, M. Bernier, D. Faucher, J. Carrier, and R. Vallee,

“3.7 W fluoride glass Raman fiber laser operating at 2231 nm,” Optics Express, vol. 20, no. 17, pp. 19412 19419, 2012.

[19] P. A. Thielen, L. B. Shaw, P. C. Pureza, V. Q. Nguyen, J. S. Sanghera, and L. D. Aggarwal, “Small-core As-Se fiber for Raman amplification,” Optics Letters, vol. 28, no. 16, pp. 1406 1408, 2003.

[20] S. D. Jackson and G. Sanchez, “A chalcogenide glass Raman fiber laser,” Applied Physics Letters, vol. 88, pp. 221106 221109, May 2006.

[21] M. Bernier, M. El-Amraoui, J. F. Couillard, Y. Messaddeq, and R. Vallee, “Writing of Bragg gratings through the polymer jacket of low-loss As2S3 fibers using femtosecond pulses at 800 nm,” Optics Letters, vol. 37, no. 18, pp. 3900 3902, 2012.

[22] M. Bernier, M. Fortin, N.Caron, M. El-Amraoui, Y. Messaddeq, and R. Vallee, “Mid-infrared chalcogenide glass Raman fiber laser,” Optics Letters, vol. 38, no. 2, pp. 127 129, 2013.

[23] M. Bernier, V. Fortin, M. El-Amraoui, Y. Messaddeq, and R. Vallee, “3.77 μm fiber laser based on cascaded Raman gain in a chalcogenide glass fiber,” Optics Letters, vol. 39, no. 7, pp. 2052 2055, 2014.

[24] G. Qin, S. Huang, H. Feng, A. Shirakawa, M. Musha, and K. I. Ueda, “Power scaling of Tm3+-doped ZBLAN blue up- conversion fiber lasers modeling and experiments,” Applied Physics, vol. 82, no. 1, pp. 65 70, 2006.

[25] J. Li, Y. Chen, M. Chen, et al., “Theoretical analysis and heat dissipation of mid-infrared chalcogenide fiber Raman laser,” Optics Communications, vol. 284, no.5, pp. 1278 1283, 2011.

[26] J. Li, Z. Ou, Z. Dai, Z. Peng, L. Zhang, and Y. Liu, “Theoretical analysis and design of Mid-infrared ZBLAN Raman fiber laser,” Infrared and Laser Engineering, vol. 40, no. 8, pp. 1432 1437, 2011 (in Chinese).

[27] H.-Y. Luo, J.-F. Li, J. Li, Y.-L. He, and Y. Liu, “Numerical modeling and optimization of mid-infrared fluoride glass Raman fiber lasers pumped by Tm3+-doped fiber laser,” IEEE Photonics Journal, vol. 5, no. 2, pp. 2700211, 2013.

[28] Y. Wang, Z. Q. Luo, F. Xiong, Z. P. Cai, and H. Y. Xu, “Numerical optimization of 3-5 μm mid-infrared ZBLAN fiber Raman lasers,” Laser & Optoelectronics Progress, vol. 51, pp. 061405, Mar. 2014 (in Chinese).

Cong Liu was born in Hubei province, China in 1990. He received the B.S. degree from University of Electronic Science and Technology of China (UESTC), Chengdu in 2013 in electronic science and technology. He is currently pursuing the M.S. degree with UESTC in optical engineering. His research interests include mid-infrared fiber lasers and nonlinear fiber optics.

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Han Zhang was born in Sichuan province, China in 1987. He received the B.S. degree in applied physics from UESTC in 2009, and the M.S. and Ph.D. degrees in optical sciences from the University of Arizona in 2011 and 2014, respectively. Since 2010, He has worked with the College of Optical Sciences, University of Arizona for four years as a research assistant and

a research associate, focusing on the super resolution microscopy study. He received the TRIF (The Technology and Research Initiative Fund) Imaging Fellowship in 2013. In 2014, he joined Douglas Scientific LLC as a senior optics engineer, leading the commercial biomedical device development. He has contributed to more than 5 commercial products worldwide. He is also the member of SPIE, OSA, and AACC. His research interests include nonlinear optics, super resolution microscopy, and gene sequencing.

Chen Wei was born in Shandong province, China in 1987. She received the B.S. degree in applied physics and the Ph.D. degree in photonics and technology from Nankai University, Tianjin in 2009 and 2014, respectively. In 2011, she joined the College of Optical Sciences, University of Arizona as a two-year visiting student. In 2014, she joined the

School of Optoelectronic Information, UESTC, where she became a lecturer in 2014. Her current research interests include mid-infrared fiber lasers and nonlinear fiber optics.

Yong Liu was born in Sichuan province, China in 1970. He received the M.S. degree from UESTC in 1994, and the Ph.D. degree from the Eindhoven University of Technology in 2004. Since 2007, he has been a professor with UESTC. He has authored and co-authored more than 180 journal and conference papers. These publications have been cited more than 1000

times (Web of Science). His research interests include optical signal processing and optical fiber technology.