Research On All-solid-state Q-switched Laser Based On Graphene Capacitor Device

All-solid-state pulsed lasers with small size,low power consumption have a wide application prospect in the fields of remote sensing,communication,medical treatment and military affairs.At present,passive Q-switching/mode-locking based on two-dimensional materials are the main techniques to obtain ultrashort pulse laser.However,it is limited by the constant absorption Coefficient of materials,this kind of laser faces the bottle-neck problems such as high power consumption,slow speed and low efficiency,which can not meet the increasing demand of practical application.In this thesis,a new type of integrated graphene-insulated layer silicon nitride-Indium tin oxide capacitor is proposed with tunable saturable absorption characteristics,it can be applied to all-solid-state CW laser systems to achieve nanosecond-level tunable pulsed laser output.The specific research contents of this thesis are as follows:(1)Graphene thin films with excellent optical properties have been prepared by using Chemical vapor deposition,on the basis of which the structure of capacitor devices has been designed.Then the carrier concentration distribution of the device under different electric field structures was studied,and the annular electrode structure was established,and the vertical structure of graphene capacitor was fabricated by microelectronic printing technology.The morphology and structure of the capacitor were characterized by SEM and Raman Spectra,and the optical and nonlinear absorption properties of the graphene capacitor were measured,the results show that the optical absorption properties of the graphene capacitor vary with the voltage..(2)The working characteristics of frequency doubling crystals are analyzed through theoretical research,PPLN frequency doubling crystals are selected according to the experimental needs and system devices,and the experimental device of 532 nm all-solid-state CW laser is designed by means of intracavity frequency doubling,and its working characteristics are studied.The prepared graphene saturable absorber was applied to this system to realize passively Q-switched pulsed laser output.When the absorbed pump power is increased from 3.12 W to 6.62 W,the pulse width is compressed from 800 ns to 280 ns,and the corresponding repetition rate is increased from 252 k Hz to 0.98 MHz.The shortest pulse width of the Q-switched pulse is 280 ns.(3)An experimental setup of a 532 nm all-solid-state pulsed laser based on graphene capacitor devices was designed,and its working characteristics were studied.When the graphene capacitor device works,the modulation voltage is used to achieve effective regulation of the output performance of the laser.When the pump power is stabilized at 1.78 W,the pulse width can be stably controlled from 1105 ns to 345 ns by voltage,and the corresponding repetition frequency is increased from 110 k Hz to 315 k Hz.Compared with a single graphene saturable absorber,the graphene capacitor device can not only achieve effective regulation of the laser output characteristics at extremely low energy consumption,but also exhibit better Q-switching performance.