Laser physics simulation Laser physics simulation programprogram Lionel CanioniLionel Canioni

University Bordeaux I FranceUniversity Bordeaux I France

The Mode programThe Mode program

Goal: visualization of laser dynamics and Goal: visualization of laser dynamics and operating types. operating types.

Interacting program working on a tabletop Interacting program working on a tabletop computercomputer

Useful for Graduate and undergraduate Useful for Graduate and undergraduate student in lasers coursesstudent in lasers courses

Illustration of the different laser operations Illustration of the different laser operations principleprinciple

Principle of workingPrinciple of working

The program:The program: Solve the laser master equation in an infinite time Solve the laser master equation in an infinite time

looploop Display continuously the physical parameters of Display continuously the physical parameters of

the laserthe laser

Calculation at each point of the cavity and for all Calculation at each point of the cavity and for all time: number of photon by mode and the time: number of photon by mode and the population difference versus frequencypopulation difference versus frequency

Physical modelPhysical model

DJDDD eq 2 dt

d

DJ JJ cdt

d 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

DeqPopulation equilibrium

SimulationsSimulations

Master equation are solve for each cavity Master equation are solve for each cavity mode with wave propagation equationmode with wave propagation equation

All the parameters let us study a large All the parameters let us study a large amount of laser typeamount of laser type

Cw laser , threshold, pulsed laser, CW Cw laser , threshold, pulsed laser, CW mode locked laser, QSwitch, mode mode locked laser, QSwitch, mode beating etc…beating etc…

Laser Dialog BoxLaser Dialog Box Cavity parametersCavity parameters

LengthLength Number of resonant optical Number of resonant optical

frequencyfrequency Optical gain mediaOptical gain media

FrequencyFrequency Emission abs cross sectionEmission abs cross section Spectral widthSpectral width Spectroscopic modelSpectroscopic model

Optical PumpingOptical Pumping CW or Pulsed pumpCW or Pulsed pump LossLoss Pump PowerPump Power

Display ControlDisplay Control Continuous or step by step Continuous or step by step

displaydisplay Choose between several Choose between several

representationrepresentation Pulse propagation parametersPulse propagation parameters

Non linear coefficient and Non linear coefficient and dispersiondispersion

Cavity parametersCavity parameters

Length in µm of the laser: Length in µm of the laser: The cavity length match The cavity length match

the gain media lengththe gain media length Small cavity for visual Small cavity for visual

mode representationmode representation

Number of resonant Number of resonant optical frequencyoptical frequency

One can choose between One can choose between 1 (single mode laser) and 1 (single mode laser) and 41 optical frequencies 41 optical frequencies allowed in the cavityallowed in the cavity

FP filter equivalentFP filter equivalent

Optical gain mediaOptical gain media FrequencyFrequency

Selection of the central Selection of the central frequency by the resonant frequency by the resonant frequency of the cavity. frequency of the cavity. Change with cavity length Change with cavity length change wavelengthchange wavelength

Spectral widthSpectral width Gain media width( arbitrary Gain media width( arbitrary

unit)unit)

Emission abs cross sectionEmission abs cross section Low gain or high gain laserLow gain or high gain laser

Spectroscopic modelSpectroscopic model Homogenous or Homogenous or

Inhomogenous model Inhomogenous model example gas laser or Nd Yag example gas laser or Nd Yag laserlaser w

Optical PumpingOptical Pumping

LossLoss Accumulated during Accumulated during

laser propagation laser propagation

CW or Pulsed pumpCW or Pulsed pump CW Pumping and CW Pumping and

flashed pump allowed flashed pump allowed Qswith simulation. Qswith simulation. Flash duration and Flash duration and repetition rate repetition rate availableavailable

Pump PowerPump Power Control the efficiency Control the efficiency

between pump power between pump power and optical transferand optical transfer

Pulse propagation parametersPulse propagation parameters

Effective parameters Effective parameters for fs propagationfor fs propagation

Second order Second order dispersion: useful for dispersion: useful for pulse stretchedpulse stretched

Nonlinear coefficient: Nonlinear coefficient: SPM mod locking : SPM mod locking : scattering of energy scattering of energy between modesbetween modes

Display ControlDisplay Control

Choose between several representation:Choose between several representation: Frequency domain: mod representation, spectrum Frequency domain: mod representation, spectrum

representationrepresentation Time domain: Difference population, output power, pulse Time domain: Difference population, output power, pulse

inside the laser rodinside the laser rod Standard value: pulse width, power, intensity, Standard value: pulse width, power, intensity,

wavelengthwavelength

Continuous or step by step display:Continuous or step by step display: Multithread application allowed permanent tuning and Multithread application allowed permanent tuning and

adjustment while displayadjustment while display

DemonstrationDemonstration

Application

ThresholdThreshold

Threshold study:Threshold study:1.1. Study of spontaneous emissionStudy of spontaneous emission

Starting the laser with Ds=DeqStarting the laser with Ds=Deq

Starting parameters: pump=0.5, Loss=0.2Starting parameters: pump=0.5, Loss=0.2

Increase pump until thresholdIncrease pump until threshold

2.2. Laser starting with Ds<DeqLaser starting with Ds<DeqStarting parameters: pump=3, Loss=0.2Starting parameters: pump=3, Loss=0.2

Observation of the oscillating behavior before steady stateObservation of the oscillating behavior before steady state

Application

Power versus lossPower versus loss

Threshold study:Threshold study:1.1. Study of spontaneous emissionStudy of spontaneous emission

Starting the laser with Ds=DeqStarting the laser with Ds=Deq

Starting parameters: pump=0.5, Loss=0.2Starting parameters: pump=0.5, Loss=0.2

Increase pump until thresholdIncrease pump until threshold

2.2. Laser starting with Ds<DeqLaser starting with Ds<DeqStarting parameters: pump=3, Loss=0.2Starting parameters: pump=3, Loss=0.2

Observation of the oscillating behavior before steady stateObservation of the oscillating behavior before steady state

Application

Homogenous Inhomogenous LaserHomogenous Inhomogenous Laser

Spectral study:Spectral study:1.1. Study of inhomogenous laserStudy of inhomogenous laser

Starting the laser with spectra and population windowStarting the laser with spectra and population window

2.2. Homogenous LaserHomogenous LaserObservation of the spectral narrowing Observation of the spectral narrowing

Application

Pump pulsed: relaxationPump pulsed: relaxation

Oscillating relaxation:Oscillating relaxation:1.1. Study of laser relaxationStudy of laser relaxation

Starting the laser with inhomogenous mediaStarting the laser with inhomogenous media

Starting parameters: pump=10, Loss=0.5Starting parameters: pump=10, Loss=0.5

Pump duration 300 fsPump duration 300 fs

Application

Pump pulsed QSwitchPump pulsed QSwitch

1.1. Study of Qswitch laserStudy of Qswitch laserStarting the laser with homogenous mediaStarting the laser with homogenous media

Starting parameters: pump=2.5, Loss=0.5Starting parameters: pump=2.5, Loss=0.5

Pump duration 100 fs check uncheck Qswitch buttonPump duration 100 fs check uncheck Qswitch button

Application

CW Mode LockingCW Mode Locking

0

50

100

0.1 0.3 0.5

Pulseduration

Intensity

Application

Pulse duration study:Pulse duration study:1.1. Long PulseLong Pulse

Starting parameters: pump=3.5, Loss=0.1Starting parameters: pump=3.5, Loss=0.1

Increase N2 for shorter pulse, Dispersion =0Increase N2 for shorter pulse, Dispersion =0

N2*10-10

CW Mode LockingCW Mode Locking

Prism tuning

0

20

40

60

80

100

29 32 35 38 Chirp

Pu

lse D

ura

tio

n

Application

Dispersion effect:Dispersion effect:1.1. Short PulseShort Pulse

Starting parameters: pump=3.5, Loss=0.1Starting parameters: pump=3.5, Loss=0.1

N2 =0.6, Dispersion between 29 and 39N2 =0.6, Dispersion between 29 and 39