飞秒脉冲激光在铁电体中的冲击受激拉曼散射

Impulsive Stimulated Raman Scattering of Femtosecond Pulse Laser in Ferroelectrics

将冲击受激拉曼散射应用于某些铁电体中 ,在时间域内分析物质晶格振动。τωα <2π是应用冲击受激拉曼散射的必要条件。使用钛宝石激光再生放大系统作为激发源 ,在LiTaO3 晶体内获得了声子电磁激元振荡模。将同种方法用于KDP ,在其铁电体相位转换点以上 5 0K的温度范围内 ,仅发现了波矢 q =6848cm- 1 ,弛豫时间常数τ0 =1 33× 10 - 1 3 s的弛豫振动软模 ,显示出KDP铁电体相位转换的弛豫特性。

Impulsive stimulated Raman scattering (ISRS) was applied to some ferroelectric crystal to analyze the vibration of the crystal lattice in time domain. For significant phonon excitation to occur, the excitation pulse duration τa. Using Ti: sapphire regenerative amplifier system as a light source, phono-polariton oscillatory modes in LiTaO3 could be observed. The method was applied to KH2PO4. Only relaxing was observed within 50 K from the ferroelectric phase transition point. The relaxation time constant τ0 is 1.33×10-13s in the wave vector q=6848 cm-1. It shows a relaxational character of the ferroelectric phase transition KH2PO4.