Sub-100 Picoseconds Ultra-narrow Pulse Generation Circuit Based On MOSFET And SRD

With the rapid development of information technology,laser diodes are widely used in various fields,and their optical pulse output characteristics can be directly modulated by the injected electrical pulses.The width,amplitude and frequency of the pulse generator are very important indicators.After investigating the current state of research on pulse generation circuits,it is found that there are relatively few pulse generation circuits that can achieve less than 100 picoseconds,and the high cost and large size of commercially available electric pulse generators make it difficult to be widely used in industry.Pulse generators based on discrete device can overcome these drawbacks and are of great interest as a drive source for laser diodes.The main work of this thesis is as follows:(1)The pulse generation module is implemented based on the switching characteristics of MOSFETs.The equivalent circuit model of MOSFETs is used as a starting point to analyze the factors affecting the switch speed of MOSFETs.By changing the circuit parameters,the effect on the output electric pulse is analyzed under different conditions.After optimizing the pulse generation module with different circuit parameters,it can output a pulse with a pulse width of 1.5 ns and an amplitude of 15.6V at 2 MHz,and a pulse with a pulse width of 1.73 ns and an amplitude of 12.2 V at 10 MHz.(2)The pulse shaping module is implemented based on the step recovery characteristics of the SRD and the transmission characteristics of the microstrip transmission line.Test and analyze the effect of different bias currents and different microstrip line lengths on the shaping performance of the pulse shaping module.With microstrip line length of 3.3 mm and bias current of 30 m A,a 1.5 ns,15.6 V pulse generated by the pre-stage module can be shaped into 9.9 V,80 ps.The shaping ratio is18.75:1.(3)The implemented ultra-narrow pulse generation circuit is used to drive a highbandwidth laser diode prepared in the laboratory.Under different electrical pulse conditions,analyzing the optical pulse characteristics of the semiconductor laser,the laser can finally generate a pulse with a pulse width of 38 ps and a peak power of 6.64 m W.Compared with the related literature published in the current research,this article first uses the switching characteristics of the MOSFET to generate high-amplitude pulses,and then uses the combination of the transmission characteristics of the microstrip line and the step characteristics of the SRD to sharpen the pre-pulse.This thesis realizes a low-cost,compact,high-amplitude,ultra-narrow pulse generator circuit below 100 picoseconds,which is important for promoting the industrialization of integrated systems of ultra-narrow pulse generators and laser diodes.