Qualitative Modelling and Simulation of Free Running Semiconductor Laser.


The thesis presents the modelling and simulation of free running semiconductor laser.

The rate equations which were derived on the basis of the fact that there must be a balance between carriers that undergo transition and the  photons generated and annihilated were simulated to examine what laser looks like when ran without positive optical feedback nor any optical injection.

The result shows the photons get amplified due to stimulated emission but no  oscillation of  the output is obtained. Such a set up is therefore seen as an optical amplifier.


Title page                       i

Acknowledgement                    ii

Abstract                                    iii

Table of Content            iv



  • Introduction 1
  • Aims of the Thesis 2
  • Overview of the Thesis 3


Physics of Semiconductor Laser

  • Spontaneous Emission 4
  • Stimulated Emission 6
  • Photon Absorption 7
  • Population Inversion 9
  • Maser and Laser Amplifier 11
  • Threshold Condition for Lasing 11
  • Pumping 13
  • Operation Principle of Semiconductor Laser 15
  • Homojunction Semiconductor Laser 17
  • Double-heterostructure Semiconductor Laser 20
  • Brief Review of Rate Equations and Semicunductor Lasers 22

CHAPTER THREE Modelling and Simulation

  • The Rate Equations 24
  • Modelling of The Rate Equations 25
  • MATLAB Simulation of The Rate Equations 31

CHAPTER FOUR Results and Discussions

  • The Plots of the Dynamics 34
  • The Carrier Density 35
  • The Photon Density 36
  • Discussions of Results 37
  • Conclusion 39

Reference                 40


The word laser is an acronym for the most significant feature of laser action: Light Amplification by Stimulated Emission of Radiation3. The basic component of laser is the material with ability to amplify radiation. Such materials are referred to as active medium.

The amplification  process results from the phenomenon known as the stimulated emission (this will be explained in chapter two) which was discovered by Albert Einstein in 1916. The first laser was constructed by T. H. Maiman in 1960 and different types have been invented ever since.

Common among the different types of laser are the solid state lasers, gas lasers, dye lasers, chemical lasers and semiconductor lasers.

Semiconductor lasers were first demonstrated in 1962 by two US groups led by Rober N. Hall at the General Electrical Research Centre and by Marshall Nathan at the IBM T. J. Watson Research Center1.


“Laser Diode”, http://en.wikipedia.org/wiki/laser_diodes, [Online]

Svelto, “Principles of Lasers”, Plenum Press, New York, 1998 http://wikipedia.org/wiki/laser_diode_rate-equations,[Onlne]

N. Hall et al, “Coherent light emission from GaAs junctions”, phys. Rev. Lett., vol.9, pp.366-367,1962

I. Nathan et al, “Stimulated emission of radiaton from GaAs p-n junctions”, Appl. Phys. Lett., vol.1, pp. 62-63, 1962

Holanyak Jr and A. F. Bevacqul, “Coherent (visible) light emission for GasAsP junctions”, App. Phys. Lett., vol.1, pp. 82-83, 1962

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