PPLN晶体中不同非共线结构光参量放大过程的带宽与增益特性

Bandwidth and Gain of PPLN based Optical Parametric Amplification with Different Noncollinear Geometries

利用非共线相位匹配方法,研究了不同极化周期和不同非共线结构下周期极化铌酸锂晶体(PPLN)中的光参量放大(OPA)带宽与增益特性。光谱带宽和增益通过对相位失配进行泰勒级数展开并保留到二阶级数项得到,在计算过程中考虑到了晶体极化周期、非共线入射结构、PPLN晶体长度以及抽运光强度的影响。计算结果表明,参量带宽和增益带宽具有相似的特性,而且PPLN晶体的周期和非共线入射结构会对光参量放大的光谱带宽产生一定的影响,在同一波长处,通过调节晶体周期或非共线结构可以获得更大的带宽。在对增益的研究过程中发现,与增加抽运光强度相比,增加晶体的长度能更有效地增强参量增益,但是PPLN晶体的周期和非共线入射结构对增益几乎没有什么影响。

The spectral bandwidth and gain of PPLN based optical parametric amplification （OPA） with different noncollinear geometries have been investigated. The spectral bandwidth and gain is determined by expanding the wave-vector mismatch in a Taylor series and retaining terms through second order. The calculation takes into account the effects of grating period, noncollinear amplification geometry, crystal＇s length and pump intensity. The results show the grating period of PPLN and the noncollinear geometry has effects on the spectral bandwidth. The characteristics of gain bandwidth are similar to those of parametric bandwidth; they are all greatly enhanced on the condition of broadband amplification. Compared with the increase of pump intensity, the gain can be effectively improved by increasing crystal＇s length, while the grating period and the noncollinear amplification geometry almost have no effect on the gain.