Research On Quenched Gaas Photoconductive S Emiconductoh Switch By Low Light Of Nano Joule Magnitude

Terahertz(THz)radiation has important scientific value and broad application prospects,where the key of technology is the generation of terahertz wave.Currently the most widely used method is through the photoconductive,using GaAs PCSS(Photoconductive semiconductor switch)antenna as terahertz radiation triggered by femtosecond laser,bring about terahertz waves in the terahertz time-domain spectroscopy system(THz-TDS).Due to the current photoconductive antenna applied to the international terahertz time-domain spectroscopy system is working in linear mode.Radiated power and efficiency of the terahertz wave is too low in this method,although the spectrum of radiated terahertz is wide enough.The path of get high power,high energy and high efficiency terahertz radiation has become an urgent problem.We know ultrafast electrical pulse power GaAs photoconductive switch output under the avalanche multiplication mode can be much greater than under the linear mode of operation.However,using GaAs photoconductive swi,tches with avalanche multiplication mechanism as a radiation source for generating THz radiation has not found in the international so far.We must solve the two core issues:Firstly avalanche multiplication effect for carrier in the GaAs PCA must meet in the trigger energy threshold and bias field threshold condition.This means it can generate photo-activated charge domain that when the bias field in GaAs PCA is over Gunn electric field threshold and trigger light carrier concentration meet to the conditions of forming the charge domain to form avalanche impact ionization of carriers;second GaAs PCA can not work at high repetition frequency state caused by "lock-in effect"(known as lock-on effect)of the current waveform,even realize femtosecond laser trigger GaAs PCA photoconductive aval anche mode.This paper discusses the possibility and progress of use GaAs photoconductive switches in the avalanche multiplication operation quenching mode as a photoconductive antenna to generate THz radiation.Through theoretical analysis and experimental inquiry,we realized experimentally:the first an nJ magnitude femtosecond laser pulse has triggered GaAs photoconductive switch into the avalanche multiplication mode,with 6 nJ femtosecond laser fired successfully,which is the minimum energy value reported in the current international.The second the delay time of carrier avalanche multiplication is reduced to 1.23 ns,when GaAs photoconductive switch realized avalanche multiplication quenching mode.It can operate at 80 MHz repetition rate and will not break down.This result laid the experimental foundation for use GaAs photoconductive switch in high power avalanche multiplication mechanism as GaAs photoconductive antennas to generate THz radiation.