Simulation of a Passively Modelocked AllFiber Joseph Shoer一个被动锁模光纤约瑟夫澡仿真.ppt

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1、Simulation of a Passively Modelocked All-Fiber Laser with Nonlinear Optical Loop Mirror,Joseph Shoer 06Strait Lab,Solitons,Direction of propagation,Left:autocorrelation of sech2 t Propagates without changing shapeCould be used for long-distance data transmission,Intensity,Distance,All Fiber Laser,Li

2、ght from,Nd:YAG,Pump Laser,Output,Nonlinear Optical Loop Mirror,Er/Yb,51.3%,48.7%,90%,10%,PolarizationController,Faraday isolator,PolarizationController,Power Transfer Curves,Transmission Model,Different PTC at each pointContours indicate light transmission through NOLM(value of PTC at zero input)as

3、 a function of NOLM polarization controller settingsBright shading indicates positive PTC slope at low inputModelocking occurs at highest low-power slope,Transmission Model,Different PTC at each pointContours indicate light transmission through NOLM(value of PTC at zero input)as a function of NOLM p

4、olarization controller settingsBright shading indicates positive PTC slope at low inputModelocking occurs at highest low-power slope,Experimental Autocorrelations,Experimental Scope Trace,Simulation Goals,Model all pulse-shaping mechanisms over many round trips of the laser cavityNOLMStandard fiberE

5、r/Yb gain fiberModel polarization dependence of NOLM(duplicate earlier model)Duplicate lab results?,Gain,Fiber,NOLM,Pulse Shaping:Fibers,Time delay,Distance of propagation,Solving Maxwells Equations in optical fibers yields the nonlinear Schrdinger equation(NLSE):The NLSE can be solved numericallyOr

6、dinary first-order solitons maintain their shape as they propagate along a fiberOther input pulses experience variations in shape,Pulse Shaping:Fibers,Time delay,Distance of propagation,Time delay,|E|2,Time delay,|E|2,Pulse Shaping:NOLM,Pulseedge,Pulsepeak,10 round trips,50 round trips,Pulse Shaping

7、:Laser Gain,Pulses gain energy as they pass through the Er/Yb-doped fiberGain must balance loss in steady stateGain saturation:intensity-dependent gain?Not expected to have an effectGain depletion:time-dependent gain?Not expected to have an effectAmplified spontaneous emission(ASE):background lasing

8、?,CalculatePTC,NOLM(apply PTC),Standard Fiber(NLSE),Er/Yb Fiber(NLSE+gain),Inject seed pulse,Output pulse after i round trips,Repeat n times,The Simulator,Adjust gain,Power Transfer Curve is determined by polarization controller settingsAbsorbs nonlinearity of NOLM fiberUses transmission model(Aubry

9、n Murray 05)fit from laboratory data,CalculatePTC,NOLM(apply PTC),Standard Fiber(NLSE),Er/Yb Fiber(NLSE+gain),Inject seed pulse,Output pulse after i round trips,Repeat n times,The Simulator,Adjust gain,In the lab,pulses are initiated by an acoustic noise burstThe model uses E(0,t)=sech(t)a soliton a

10、s a standard input profileThis is for convenience with enough CPU power,we could take any input and it should evolve into the same steady state result,CalculatePTC,NOLM(apply PTC),Standard Fiber(NLSE),Er/Yb Fiber(NLSE+gain),Inject seed pulse,Output pulse after i round trips,Repeat n times,The Simula

11、tor,Adjust gain,2 m of Er/Yb-doped fiber is simulated by solving the Nonlinear Schrdinger Equation with a gain termThe program uses an adaptive algorithm to settle on a working gain parameterDispersion and self-phase modulation are also included hereASE is added here as a constant offset or as rando

12、m noise,CalculatePTC,NOLM(apply PTC),Standard Fiber(NLSE),Er/Yb Fiber(NLSE+gain),Inject seed pulse,Output pulse after i round trips,Repeat n times,The Simulator,Adjust gain,NOLM is simulated by applying the PTC,which tells us what fraction of light is transmitted for a given input intensityThis meth

13、od neglects dispersion in the NOLM fiberFortunately,we use dispersion-shifted fiber in the loop!,CalculatePTC,NOLM(apply PTC),Standard Fiber(NLSE),Er/Yb Fiber(NLSE+gain),Inject seed pulse,Output pulse after i round trips,Repeat n times,The Simulator,Adjust gain,13 m of standard communications fiber

14、is simulated by solving the Nonlinear Schrdinger EquationSoliton shaping mechanisms,dispersion and SPM,come into play hereSteady-state pulse width is the result of NOLM pulse narrowing competing with soliton shaping in fibersAll standard fiber in the cavity is lumped together in the simulator,Calcul

15、atePTC,NOLM(apply PTC),Standard Fiber(NLSE),Er/Yb Fiber(NLSE+gain),Inject seed pulse,Output pulse after i round trips,Repeat n times,The Simulator,Adjust gain,Output pulses from each round trip are stored in an arrayWe can simulate autocorrelations of these pulses individually,or averaged over many

16、round trips to mimic laboratory measurementsUnlike in the experimental system,we get to look at both pulse intensity profiles and autocorrelation traces,CalculatePTC,NOLM(apply PTC),Standard Fiber(NLSE),Er/Yb Fiber(NLSE+gain),Inject seed pulse,Output pulse after i round trips,Repeat n times,The Simu

17、lator,Adjust gain,CalculatePTC,NOLM(apply PTC),Standard Fiber(NLSE),Er/Yb Fiber(NLSE+gain),Inject seed pulse,Output pulse after i round trips,Repeat n times,The Simulator,Adjust gain,Simulation Results,Simulation for 50 round trips results averaged over last 40 round tripsPositive PTC slope at low p

18、owerNo ASE,I(a.u.),t(ps),simulator outputsech(t)2,Simulation Results,Simulation for 50 round trips results averaged over last 20 round tripsNegative PTC slope at low powerNo ASE,I(a.u.),t(ps),Simulation Results,Simulation for 50 round trips results averaged over last 40 round tripsPositive PTC slope

19、 at low powerASE:Random intensity noise added each round trip(max 0.016),I(a.u.),t(ps),Simulation Results,Simulation for 50 round trips results averaged over last 40 round tripsPositive PTC slope at low powerASE:Random intensity noise added each round trip(max 0.016),I(a.u.),t(ps),Simulation Results

20、,Simulation for 50 round trips results averaged over last 40 round tripsPositive PTC slope at low powerASE:Constant intensity background added each round trip(0.016),I(a.u.),t(ps),Simulation Results,Simulation for 50 round trips results averaged over last 40 round tripsPositive PTC slope at low powe

21、rASE:Random intensity noise added each round trip(max 0.009),I(a.u.),t(ps),No ASE,0.016 ASE,Future Work,Obtain a new transmission map so the simulator can make more accurate predictionsProduce quantitative correlations between simulated and experimental pulsesPeak intensity,background intensity,wing

22、 sizeDetermine the quantitative significance of simulation parametersAre adaptive gain and amount of ASE reasonable?,Conclusions,Investigation of each mechanism in the simulator helped us better understand the laserThe simulator can produce qualitative matches for each type of pulse the laser emits

23、near-soliton pulsesThe overall behavior of the simulator matches the experimental system and our theoretical expectationsThe simulator has allowed us to explain autocorrelation backgrounds,wings,and dips as results of amplified spontaneous emissionThe simulator can now be refined and become a standard tool for investigations of our fiber laser,