基于飞秒瞬态反射技术的单晶硅薄膜超快动力学研究

Ultrafast Dynamics Study of Crystalline Silicon Film Based on the Femtosecond Laser Transient Reflection Technique

以飞秒激光放大器作为光源,利用瞬态反射实验技术研究了厚度为1000 nm的单晶硅薄膜瞬态反射率变化过程.实验系统采用激光脉宽为120 fs,泵浦光波长为400 nm,探测光波长为800 nm.实验结果表明:随着泵浦光照射到样品表面后,样品表面的反射率变化在百飞秒内迅速增加到峰值,之后伴随着数皮秒的弛豫过程反射率的变化速率逐渐放缓.利用双e指数函数拟合出不同激光脉冲作用下反射率变化的快弛豫时间.并建立了TTM-Drude模型,分析了飞秒激光与单晶硅薄膜表面相互作用后电子温度和晶格温度的变化过程,得到不同脉冲能量作用下电子-晶格温度变化曲线,并分析了快弛豫过程中发生的物理过程.

As a light source,a femtosecond laser amplifier was used to study the transient reflectance change of a single crystal silicon thin film with a thickness of 1000 nm by a transient reflection experiment technique. The experimental system uses a laser pulse width of 120 fs,a pump light wavelength of 400 nm,and a probe light wavelength of 800 nm. The experimental results show that： after experiencing a sharp decline in the first few picoseconds,the reflectivity starts a relatively slow recovery process to the equilibrium state,and the double e-exponential function is used to fit the fast relaxation times of the reflectivity changes under different laser pulses. The TTM-Drude model was established to analyze the changes of the electron temperature and lattice temperature after interaction between the femtosecond laser and the monocrystalline silicon film. The electron-lattice temperature variation curves under different pulse energies were obtained,and the physical processes occurring during fast relaxation was analyzed.