# Laser physics simulation program Lionel Canioni University Bordeaux I France.

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Laser physics simulation program Lionel Canioni University Bordeaux I France

The Mode program  Goal: visualization of laser dynamics and operating types.  Interacting program working on a tabletop computer  Useful for Graduate and undergraduate student in lasers courses  Illustration of the different laser operations principle

Principle of working  The program:  Solve the laser master equation in an infinite time loop  Display continuously the physical parameters of the laser  Calculation at each point of the cavity and for all time: number of photon by mode and the population difference versus frequency

Physical model E1 E2     Interaction media EM wave Relaxation, pumping Population evolution: Population evolution: D=N2-N1 Intensity evolution: Intensity evolution: J Cavity loss, abs Laser Gain D eq  Population equilibrium

Simulations  Master equation are solve for each cavity mode with wave propagation equation  All the parameters let us study a large amount of laser type  Cw laser, threshold, pulsed laser, CW mode locked laser, QSwitch, mode beating etc…

Laser Dialog Box  Cavity parameters  Length  Number of resonant optical frequency  Optical gain media  Frequency  Emission abs cross section  Spectral width  Spectroscopic model  Optical Pumping  CW or Pulsed pump  Loss  Pump Power  Display Control  Continuous or step by step display  Choose between several representation  Pulse propagation parameters  Non linear coefficient and dispersion

Cavity parameters  Length in µm of the laser:  The cavity length match the gain media length  Small cavity for visual mode representation  Number of resonant optical frequency  One can choose between 1 (single mode laser) and 41 optical frequencies allowed in the cavity  FP filter equivalent

Optical gain media  Frequency  Selection of the central frequency by the resonant frequency of the cavity. Change with cavity length change wavelength  Spectral width  Gain media width( arbitrary unit)  Emission abs cross section  Low gain or high gain laser  Spectroscopic model  Homogenous or Inhomogenous model example gas laser or Nd Yag laser

Optical Pumping  Loss  Accumulated during laser propagation  CW or Pulsed pump  CW Pumping and flashed pump allowed Qswith simulation. Flash duration and repetition rate available  Pump Power  Control the efficiency between pump power and optical transfer

Pulse propagation parameters  Effective parameters for fs propagation  Second order dispersion: useful for pulse stretched  Nonlinear coefficient: SPM mod locking : scattering of energy between modes

Display Control Choose between several representation:  Frequency domain: mod representation, spectrum representation  Time domain: Difference population, output power, pulse inside the laser rod  Standard value: pulse width, power, intensity, wavelength Continuous or step by step display:  Multithread application allowed permanent tuning and adjustment while display

Demonstration

Threshold Threshold study: 1. Study of spontaneous emission Starting the laser with Ds=Deq Starting parameters: pump=0.5, Loss=0.2 Increase pump until threshold 2. Laser starting with Ds<Deq Starting parameters: pump=3, Loss=0.2 Observation of the oscillating behavior before steady state

Power versus loss Threshold study: 1. Study of spontaneous emission Starting the laser with Ds=Deq Starting parameters: pump=0.5, Loss=0.2 Increase pump until threshold 2. Laser starting with Ds<Deq Starting parameters: pump=3, Loss=0.2 Observation of the oscillating behavior before steady state

Homogenous Inhomogenous Laser Spectral study: 1. Study of inhomogenous laser Starting the laser with spectra and population window 2. Homogenous Laser Observation of the spectral narrowing

Pump pulsed: relaxation Oscillating relaxation: 1. Study of laser relaxation Starting the laser with inhomogenous media Starting parameters: pump=10, Loss=0.5 Pump duration 300 fs

Pump pulsed QSwitch 1. Study of Qswitch laser Starting the laser with homogenous media Starting parameters: pump=2.5, Loss=0.5 Pump duration 100 fs check uncheck Qswitch button

CW Mode Locking Pulse duration study: 1. Long Pulse Starting parameters: pump=3.5, Loss=0.1 Increase N2 for shorter pulse, Dispersion =0 N2*10 -10

CW Mode Locking Dispersion effect: 1. Short Pulse Starting parameters: pump=3.5, Loss=0.1 N2 =0.6, Dispersion between 29 and 39

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