Simulation of semiconductor laser using circuit level modeling

Tan , Chee Leong (2007) Simulation of semiconductor laser using circuit level modeling. Masters thesis, Universiti Malaysia Sabah.

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Abstract

Semiconductor laser is an important optical source used in various applications. A model of laser is required to simulate its performance before fabrication. In the past few decades, many laser models are developed using different types of modeling techniques. Analyses of these lasers are normally carried out by numerically solving the rate equations. Circuit simulation is one of the tools for the design and analysis of the relatively complex circuits such as semiconductor laser, which can include the parasitic and driver Circuitry. In this thesis four different types of laser structures, namely double heterostructure (DH), quantum well (QW), vertical cavity (VC) and hybrid bistable laser are developed. These circuit models are analyzed using PSPICE circuit Simulator. large and small signal circuit models for double heterostructure laser diodes are developed from the rate equations. The models include both single and multi mode operations of the DH laser. The effects of coupling coefficient, parasitics circuit, driver circuit and gain compression are studied in detail. The l-I curve, transient response and frequency response analysis are studied and it shows good agreement with the experimental results. A circuit model of quantum well laser based on the 3 level rate equations is also developed. The temperature effect on the laser behaviour is studied by incorporating equivalent thermal circuit model into the laser model. The effects of temperature, leakage current and heat dissipation are also considered in the equivalent thermal model. The effect of bias current on the transient behaviour of QW laser at various temperatures is studied. It is found that the laser performance is a function of separate confinement heterostructure (SCH) region length. It is observed that the modulation response of QW laser with shorter separate confinement heterostructure length is more sensitive to the temperature variation. The effect of temperature on multimode and frequency response of the QW laser is also simulated. An increase in temperature reduces the operating frequency and resonance peak shift to higher frequency. The vertical cavity surface emitting (VCSEL) laser model is developed. The rate equations included the carrier density flow in the SCH region of VCSEL and the logarithm gain is used as the gain constant. Optical output increases with input current up to 11mA and decreases afterward at 300K. This turn over is varies with temperature. It is found that the VCSEL is sensitive to the temperature due to the Distributed Bragg Reflectors (DBR) structures. DBR structure also causes loss such as leakage current increases exponentially with input current. The turn on delay behaves oppositely due to the dynamic increase in leakage current at higher temperature. A hybrid bistable semiconductor laser (HBSL) device is proposed to overcome the temperature sensitivity problem of VCSEL. The quantum well laser is used as the gain element of the bistable laser and VCSEL is used as the absorber element. The equivalent circuit model is developed based on the rate equations derived. The hybrid semiconductor laser consisting of edge emitting QWL and VCSEL exhibits bistability. The hysterisis width and threshold current can be controlled by source resistance as well as by the device dimensions. Symmetrical self-pulsation is also observed in HBSL by fine-tuning the load resistance value to 100 ohm, the VCSEL region is biased at 55 mA within the bistable region and a positive pulse of 10mA height and 25ns width is applied to the QWL

Item Type:Thesis (Masters)
Uncontrolled Keywords:simulation, semiconducor laser, hybryd bistable semiconductor laser (HBSL), vertical cavity surface enitting laser (VCSEL), separate confinement heterostructure (SCH)
Subjects:T Technology > TA Engineering (General). Civil engineering (General)
Divisions:SCHOOL > School of Engineering and Information Technology
ID Code:6446
Deposited By:IR Admin
Deposited On:28 Jun 2013 10:17
Last Modified:28 Jun 2013 10:17

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