Sabaeian Mohammad, Motazedian Alireza, Mohammad Rezaee Mostafa, Jalil-Abadi Fatemeh Sedaghat
Appl Opt. 2014 Nov 10;53(32):7691-6. doi: 10.1364/AO.53.007691.
In this work, a three-dimensional and time-dependent nonlinear wave model to describe the generation of pulsed Bessel-Gauss second-harmonic waves (SHWs) is presented. Three coupled equations, two for ordinary and extraordinary fundamental waves and one for extraordinary SHWs, describing type II second-harmonic generation (SHG) in a KTiOPO (KTP) crystal were solved by considering the depletion of fundamental waves (FWs). The results examined the validity of nondepleted wave approximation against the energy of pulses, beam spot size, and interaction length. It was shown that for pulses with spot sizes of ω=80 μm and energy of 0.8j, the nonlinear interaction was accomplished over a distance of ∼5 mm. Therefore, for KTP crystals with lengths longer than 5 mm, the nondepleted wave approximation can no longer be valid. To be valid, the crystal must be shorter than the interaction length, i.e., 5 mm.
在这项工作中，提出了一个三维且与时间相关的非线性波动模型，用于描述脉冲贝塞尔 - 高斯二次谐波（SHW）的产生。通过考虑基波（FW）的耗尽，求解了描述KTiOPO（KTP）晶体中II型二次谐波产生（SHG）的三个耦合方程，其中两个用于寻常和非寻常基波，一个用于非寻常二次谐波。结果针对脉冲能量、束斑尺寸和相互作用长度检验了非耗尽波近似的有效性。结果表明，对于光斑尺寸为ω = 80μm且能量为0.8j的脉冲，非线性相互作用在约5mm的距离上完成。因此，对于长度超过5mm的KTP晶体，非耗尽波近似不再有效。要使其有效，晶体必须短于相互作用长度，即5mm。
