Research On Response Characteristics Of Semiconductor Lasers And Photodetectors

Wireless optical communication,which uses laser as the information carrier,has the characteristics of high bandwidth,low cost,free from the.restriction of frequency spectrum It has attracted widespread attention in recent years.Semiconductor laser diode(LD)and PIN photodetector(PIN-PD)are important transmitting and receiving devices in wireless optical communication system and high-speed information transmission field.Their working characteristics directly affect the performance of the whole communication system.Therefore,it is of great significance to study the dynamic response characteristics of LD and PIN-PD.The main works of this thesis are as follows:1.Based on the rate equation,the equivalent circuit model of the double heterojunction semiconductor laser(DH-LD)is established,the analytical expression of relaxation oscillation frequency is solved.The modulation response,pulse response and in put-output characteristics of semiconductor lasers are simulated by using PSPICE general,circuit simulation software,and these basic characteristics correctly reflect the actual operation of the device.On this basis,the influence of the relaxation oscillation frequency parameters on the modulation response characteristics and pulse response characteristics of the laser is analyzed,the influence of the resonant circuit composed of package parasitic parameters on the modulation response characteristics of the laser is discussed,the influence of temperature on the input-output characteristics of the laser is studied.2.Based on the carrier rate equation,the various parasitic parameters in the detector are coinsidered in cdetail,an d the equivalent circuit model of the PIN photodetector is establishecd.The pulse response,frequency response and voltage-current characteristics of PIN photodetector are simulated by PSPICE.On this basis,the effects of reverse bias voltage,I-zone width,photosensitive surface,chip parasitic parameters,package parasitic parameters on the pulse response characteristics and frequency response characteristics of PIN photodetectors are discussed,the effect of light intensity on voltage-current characteristics of detector is studied.The results show that:(1)For semiconductor lasers,the pulse waveform distortion can be suppressed and modulation frequency can be increased by increasing the bias current and differential gain factor,reducing the reflectivity and gain saturation factor;the modulation bandwidth can be extended by selecting appropriate package parasitic parameter values;lowering the temperature can reduce the threshold current and increase the external differential quantum efficiency.(2)For PIN photodetectors,the pulse waveform distortion can be suppressed and frequency response bandwidth can be improved by increasing the reverse bias voltage,reducing the photosensitive surface and chip parasitic capacitance and resistance value,selecting the appropriate I-zone width;the frequency response bandwidth can be extended by the resonant effect of the parasitic inductance and reducing the package parasitic capacitance and resistance value;Increasing the light intensity can increase the output photocurrent.High-speed and high-quality information transmission of the entire communication system is achieved by optimizing the response characteristics of the semiconductor laser and the PIN photodetector.