Steady State Simulation of Semiconductor Optical

Amplifier

byMr. Abdulrahman Alosaimi

Outline

• Introduction

• Basic Descriptions of Optical amplifier

• Types of Semiconductor Optical Amplifiers

• Optical Amplifications Principles

• Physical Structure of Semiconductor Optical Amplifier

• Numerical Simulation and Algorithms

• Travelling Wave Equations for Signal Fields

• Travelling Wave Equations for Spontaneous Emission

• Carrier Density Rate Equation

• Steady State Numerical Algorithm• Results

IntroductionBasic Descriptions of Optical amplifier

• An SOA is an optoelectronic device that under suitable operating conditions can amplify an input light signal.

• A schematic diagram of a basic SOA is shown in Fig. (A).• The active region in the device imparts gain to an input signal. • An external electric current provides the energy source that enables

gain to take place.

Types of Semiconductor Optical Amplifiers

• The Fabry Perot SOA (FP-SOA) where reflections from the end facets are significant (i.e. the signal undergoes many passes through the amplifier).

• The travelling-wave SOA (TW-SOA) where reflections are negligible (i.e. the signal undergoes a single-pass of the amplifier). Anti-reflection coatings can be used to create SOAs with facet reflectivities The TW-SOA is not as sensitive as the FP-SOA to fluctuations in bias current, temperature and signal polarization.

Optical Amplifications Principles

Physical Structure of Semiconductor Optical Amplifier

Fig. : Double-heterostructure (DH) semiconductor Optical Amplifiers

Numerical Simulation and Algorithms• The model is based on a set of coupled differential

equations that describe the interaction between the internal variables of the amplifier

• Travelling Wave Equations for Signal Fields• Travelling Wave Equations for Spontaneous Emission• Carrier Density Rate Equation

Travelling Wave Equations for Signal Fields

Es+ and Es- propagating in the positive and negative z directions respectively, z lies along the amplifier axis with its origin at the input facet.where and α is the material loss coefficientГ is optical confinement factorβ signal propagation coefficientgm(ѵ,n) material gain coefficient

Travelling Wave Equations for Spontaneous Emission

N+, N- are defined as the spontaneous emission photon rates (1/sec)Rsp represents the spontaneously emitted noise coupled into N+, N-

Carrier Density Rate Equation

The carrier density n(z) obeys the rate equation

I is the amplifier bias currente is the electronic charged is SOA thicknessL is SOA active region lengthW is SOA active region widthR(n) contain the radiative and nonradiative carrier recombination rate

Steady State Numerical Algorithm

• The amplifier is split into a number of sections. The signal fields and spontaneous emission photon rates are estimated at the section interfaces. The carrier density is estimated at the centre of each section.

Results

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Optical spectrum analyser display of SOA output. Resolution bandwidth = 0.1 nm

Predicted SOA output spectrum versus wavelength

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Wavelength (nm)

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Optical spectrum analyser display of SOA output. Resolution bandwidth = 0.1 nm

predicted gain profile with input signals

• Predicted forward and backward signal propagation as a function of spatial distribution