光学学报, 2010, 30 (9): 2634, 网络出版: 2014-05-15
折射率线性调制晶体中的稳态倍频研究
Research on Static Frequency Doubling in RefractiveIndex Modulated Crystals
非线性光学 倍频 折射率调制 转换效率 nonlinear optics frequency doubling refractive index modulation conversion efficiency
摘要
从麦克斯韦方程出发,推导了折射率线性调制介质内的平面波倍频耦合波方程,并给出了稳态耦合波方程的小信号解。由菲涅耳函数所描述的小信号解给出了不同于典型sinc函数的失谐函数结构。分析结果表明,折射率线性调制晶体相对于普通非线性晶体具有更大的匹配带宽,从而拥有更大的可接受温度和匹配角以及光谱带宽;然而这种带宽的增加是以牺牲整体的转换效率为代价的。值得关注的是通过选取特定的折射率调制参量可使失谐函数平坦化,这降低了倍频晶体对于由环境温度、机械结构等原因造成的工作点漂移的灵敏度。通过高转换效率下的数值模拟发现,失谐函数特性仍与低转换效率下的基本结论相符,只是在数值上略有不同且依赖于耦合强度。
Abstract
Starting from the Maxwell equations, a set of coupled planewave equations of frequency doubling in the refractiveindex modulated medium is derived, and a solution to the equations is given under the smallsignal approximation. The smallsignal solution, a form composed of Fresnel functions presents a special dephasing structure which is different from the typical sinc function. Analysis shows that the refractiveindex modulated crystal has a larger phase matching bandwidth than that in a normal nonlinear crystal, so possesses larger temperature, phase matching ange and spectral bandwidths; however the total conversion efficiency has to make sacrifice to pay for this enhancement of bandwidths. It should be noted that the dephasing function can be flattened with a suitable modulating parameter, which will lower the sensitivities of the frequency doubling crystal to erratic shifts of working points out of any thermal and mechanical reasons. It is found by a simulation in the high conversion efficiency case, the characteristics of dephasing function are still in accordance with the result from the smallsignal approximation, except rendering a magnitude difference which depends on coupling strength.
黄金哲, 毛蓓丽, 戴菡, 沈涛, 张留洋. 折射率线性调制晶体中的稳态倍频研究[J]. 光学学报, 2010, 30(9): 2634. Huang Jinjer, Mao Beili, Dai Han, Shen Tao, Zhang Liuyang. Research on Static Frequency Doubling in RefractiveIndex Modulated Crystals[J]. Acta Optica Sinica, 2010, 30(9): 2634.