Study On Photorefractive Effect Of Response Material AlGaAs In All-optical Solid-state Framing Camera

High-speed optical photography is an important means of detection and recording in industrial production and scientific research,and it is particularly important in the field of microscopic research.Most of today's cutting-edge scientific research,such as high-energy density physics research,biochemical process research,etc.,have high requirements for the space-time resolution of detection equipment.In order to further improve the performance index of ultra-fast 2D imaging equipment,an all-optical framing camera is proposed.In this system,the core key is its signal light response module,in which the response material is the research focus of this topic.III-V ternary compound aluminum gallium arsenide(AlxGa1-xAs)semiconductor is mature in preparation process,energy band can be adjusted,and response time is short.In all-optical solid framing camera,all-optical solid stripe camera,all-optical modulator,all-optical switch,etc.Widely used in devices.Among them,the photorefractive effect of AlxGa1-xAs materials is the physical basis of these devices,which will directly affect the physical limits of the key indicators of these devices.The physical time resolution limit of the all-optical solid framing camera is determined by the photorefractive time of the responsive material AlxGa1-xAs,and the response sensitivity is determined by the refractive index change of the photorefractive change of AlxGa1-xAs.To improve the performance index of all-optical solid framing camera,theoretical analysis and experimental research on the photorefractive effect of AlxGa1-xAs are needed to obtain the key factors affecting the photorefractive effect,and analyze which factors can be artificially controlled to better design.And preparing a response material.In this paper,the photorefractive effects of AlxGa1-xAs materials are studied from two aspects:theoretical model and experimental verification.Semiconductor photorefractive effect refers to the process in which a photoexcited semiconductor generates a large number of unbalanced carriers,thereby changing the optical properties such as the optical absorption coefficient,refractive index,and reflectivity of the semiconductor.The duration of the process will be determined by the lifetime of the unbalanced carriers.Therefore,the theoretical modeling part will be divided into two parts,the refractive index changes with the carrier concentration and the carrier concentration evolution law.In the experimental part,the femtosecond time-resolved pump detection experiment was used to record the refractive index change process of the AlxGa1-xAs photorefractive effect.The specific research contents are as follows:1.Calculation of the relationship between the refractive index of AlxGa1-xAs and the concentration of unbalanced carriers.The semiconductor generates a large number of unbalanced carriers after being excited by light,and generates physical mechanisms such as band-filling,band gap renormalization,and free carrier absorption to change the energy band of the semiconductor,thereby changing optical properties such as refractive index.Based on the basic properties of AlxGa1-xAs,this paper calculates the relevant parameters of the refractive index change.2.Research on the non-equilibrium carrier decay process of AlxGa1-xAs.The unbalanced carriers generated by the semiconductor after being excited by light will be degraded by the recombination process,which includes direct recombination and indirect recombination.This paper focuses on the effects of direct and indirect composites on carrier lifetime and analyzes the causes of indirect recombination.3.Preparation and experiment of AlxGa1-xAs materials.AlxGa1-xAs was grown by molecular beam epitaxy and monitored by high-resolution X-ray diffractometer.At different growth temperatures,AlxGa1-xAs has different defect concentrations.The lower the growth temperature,the higher the defect concentration.A pump detection platform was built to test AlxGa1-xAs,and the refractive index evolution of AlxGa1-xAs under pumping light excitation at different growth temperatures was observed and recorded.The results reveal the physical mechanism of the ultrafast photorefractive effect of the compound semiconductor AlxGa1-xAs.Based on this theory,a semiconductor response material with a refractive index change time of less than 5 ps is prepared.