二次晶体中准相位匹配孤子的激发与传输

Excitation and Transmission of Quasi-Phase-Matched Solitons in Quadratic Crystals

采用分步积分法,研究了形状为双曲正割平方的光束在线性和非线性极化率均被调制的一维准相位匹配(QPM)二次晶体中的传输特性。数值计算表明.在仅有基波(FW)注入的情况下,基波迅速激发出基态孤子,并呈现出固有的振荡态,二次谐波(SHW)虽然激发出谐波孤子,但相应的色散波现象比较明显;在同时注入基波与二次谐波的情况下,当它们的振幅和光束宽度满足一定条件时,两者均能够激发出稳定的孤子态,并且基态孤子的振荡更具周期性,二次谐波的色散波现象显著减弱。同时,注入的二次谐波的振幅存在一个临界值,可使激发的二次谐波孤子达到最佳孤子态。

In one-dimensional quadratic crystals with modulation of both the linear and nonlinear susceptibilities, the transmission properties of the beam, whose wave form is the square of hyperbolic secant, are investigated by split- step integral approach. Numerical calculations indicate that fundamental soliton is rapidly excited when only fundamental wave （FW） is launched, and it presents inherent oscillation. The second harmonic wave （SHW） excites soliton, but the corresponding dispersive wave is obvious. However, while both FW and SHW are launched, and their amplitudes and beam widths are appropriate, both excited solitons are stable. The periodicity of fundamental soliton oscillation is move evident, and the dispersive wave of SHW is extremely weak. Moreover, there is a critical value of the launched SHW amplitude for the excited soliton to reach the optimum state.