| Ultrafast spectroscopy has very broad application prospects in all aspects of scientific research,because it can provide ultra-high time resolution,can observe the microscopic processes in the material,and allow us to recognize scatter electrons and electrons inside semiconductors and other materials.There is a clear understanding of dynamic processes such as migration.At present,we have not studied the microscopic process of carrier dynamics when materials are excited by light.We often use some simple tools to study the electro-optic properties of materials.Ultrafast terahertz spectroscopy can be used to study the non-equilibrium carrier lifetime of semiconductors and other materials,the influencing factors of carrier relaxation process,and the photoelectric conductivity.These studies not only provide a deeper understanding of the photoelectric properties of these materials when they are excited by light,but also provide experimental evidence for the development of new devices based on these materials.The main research contents of this article are as follows:（1）Systematic research on optically pumped terahertz detection spectroscopy technology,including:generation and detection of terahertz waves,principles of optically pumped detection,carrier dynamics theory,data based on optically pumped terahertz detection spectroscopy Processing methods and experimental research.（2）Silicon（Si）,gallium arsenide（GaAs）,and low-temperature growth gallium arsenide（LT-GaAs）are widely used in many fields,but the carrier mobility and carrier concentration of these materials under light excitation Such changes are not particularly clear.The photo-induced electrical conductivity of these typical semiconductor materials was fitted by the Drude-Smith model,and the factors affecting the photo-induced electrical conductivity of the semiconductor materials were studied.（3）The exponential model formula was used to fit the process of the free carrier recovery from the excited state to the equilibrium state under light excitation,and the factors affecting the life of the carrier were studied.Studies have shown that properly increasing the defect concentration in GaAs and other materials can greatly reduce the life of the carrier,which can be explained according to the physical model;under different wavelength excitation conditions,the same material exhibits different relaxation processes,which is different from The energy level structure of the material is related.（4）Finally,taking the bismuth selenide（Bi2Se3）film as an example,the optical and electrical properties of the topological insulator material are explored and studied. |
