As passively modelocked fiber lasers based on Nonlinear Polarization Rotation(NPR) have the problem of low stability and difficulty to selfstart into a modelocking state during operation
an online automatic modelock circuit was designed to adjust the laser in real time to get a stable modelocked output. In the design
the signal from NPR passively modelocked laser was transformed to an electrical pulse signal with a high speed photoelectric detector
and it was amplified and shaped linearly to be received by the Micro Computer Unit(MCU) to count. Then the MCU distinguished the state of the laser based on quick modelock judge algorithm and adjusted the electric controlled polarization controller (PC) on the fiber laser automatically. The experiment results show that for the NPR modelocked fiber laser with a repetition rate of 6.238 MHz
the automatic modelock circuit can distinguish the losing lock in 6 ms
and can find and get into the modelock state in 10.24 s automatically. For NPR passive modelocked fiber lasers with repetition rate lower than 16 MHz
this automatic modelock circuit can get into a stable modelocked state quickly or restart immediately if the modelock state is lost for some reasons,which reaches the design requirements and shows advantages of simple structures
low costs
low powers
and high reliability.
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references
[1]MATSAS V J,NEWSON T P,RICHARDSON D J,et al..Self starting passively modelocked fiber ring soliton laser exploiting nonlinear polarization rotation [J]. Electron. Lett.,1992, 28(15):13911393.[2]DULING I N.Allfiber ring soliton laser mode locked with a nonlinear mirror[J].Opt. Lett., 1991,16(8):539541.[3]ZHAO Y, MIN S, WANG H ,et al.. Highpower figureofeight fiber laser with passive subring loops for repetition rate control[J].Opt. Express,2006,14(22):1047510480. [4]NICHOLSON J W,RAMACHANDRAN S, GHALMI S. A passively modelocked, Ybdoped, figureeight, fiber laser utilizing anomalousdispersion higherordermode fiber[J].Opt.Express,2007,15(11):66236628. [5]KUZIN E A,IBARRAESCAMILLA B,GARCIAGOMEZ D E,et al..Fiber laser mode locked by a Sagnac interferometer with nonlinear polarization rotation [J]. Opt. Lett. ,2001,26(20):15591561.[6]IBARRAESCAMILLA B,POTTIEZ O,HAUS J W,et al..Wavelengthtunable picosecond pulses from a passively modelocked figureeight Erbiumdoped fiber laser with a Sagnac fiber filter [J].J. Eur. Opt. Soc.,2008,3:14.[7]高伟清,许立新,明海,等. 正色散腔被动锁模掺铒光纤激光器的理论分析[J]. 中国激光,2009(1):8286.GAO W Q,XU L X,MIN H,et al..Theoretical analysis of passively modelocked erbiumdoped fiber laser with positive dispersion cavity [J].Chinese Journal of Lasers,2009(1):8286.(in Chinese)[8]张祖兴,戴国星.全正色散耗散孤子掺镱光纤激光器[J]. 光学学报,2011(2):0214005.ZHANG Z X,DAI G X.Allnormaldispersion dissipative soliton ytterbiumdoped fiber laser without additional filter [J]. Acta Optica Sinica. 2011(2): 0214005.(in Chinese)[9]况庆强,桑明煌,聂义友,等. 被动锁模掺铒光纤激光器中的有理数谐波锁模[J]. 光学 精密工程,2009,17(11):27192723.KUANG Q Q,SANG M H,NIE Y Y,et al.. Rational harmonic modelocking of passively modelocked erbiumdoped fiber laser[J]. Opt. Precision Eng.,2009,17(11):27192723. (in Chinese)[10]刘亮, 崔俊伟, 李文景, 等. LD泵浦的准连续输出双包层掺镱光纤激光器[J]. 中国光学, 2012,5(6):663670.LIU L, CUI J W, LI W J, et al.. Yb3+doped doubleclad quasicontinuous wave fiber laser pumped by laser diode[J]. Chinese Optics, 2012,5(6):663670.(in Chinese)[11]TAMURA K, IPPEN E P, HAUS H A, et al.. 77fs pulse generation from a stretchedpulse modelocked allfiber ring laser[J]. Optics Letters, 1993,18(13):10801082.[12]ZHOU X Y, YOSHITOMI D, KOBAYASHI Y, et al.. Generation of 28fs pulses from a modelocked ytterbium fiber oscillator[J]. Optics Express, 2008,16(10): 70557059.[13]阿戈沃.非线性光纤光学原理及应用[M].第二版.北京:电子工业出版社,2010.GOVIND P.Agrawal Nonlinear Fiber Optics,Fourth Edition & Applications of Nonlinear Fiber Optics[M].2nd ed..Beijing: Publishing House of Electronics Industry,2010.(in Chinese)