Wang M, Wada O, Koga R
Appl Opt. 1996 Jul 1;35(19):3459-65. doi: 10.1364/AO.35.003459.
Parabolic mirror optics to collimate the crescent-shaped blue laser beam that radiates from Čerenkov second-harmonic generation (SHG) in a channel waveguide configuration is proposed. Mirror collimation optics has a large tolerance to the variations of SHG element parameters, such as the laser source wavelength, as well as to mirror displacement. The anisotropy of a nonlinear crystal in which the waveguide is fabricated has been taken into account. The optimum mirror alignment to obtain a collimated blue laser beam is evaluated in terms of Marechal's criterion. The minimum wave-front aberration with beam intensity weighted is 0.054 λSH. The convergence of the collimated beam is less than 1.6 mrad, and, by using an objective lens, the collimated beam can be focused to a diameter of less than 1 µm, which is 1.27 times the diffraction-limited focusing point.
提出了一种抛物面镜光学系统，用于准直在通道波导配置中由切伦科夫二次谐波产生（SHG）辐射出的月牙形蓝色激光束。镜准直光学系统对SHG元件参数的变化（如激光源波长）以及镜位移具有很大的容差。已考虑到制造波导的非线性晶体的各向异性。根据马雷夏尔准则评估获得准直蓝色激光束的最佳镜对准。光束强度加权后的最小波前像差为0.054λSH。准直光束的会聚角小于1.6毫弧度，并且通过使用物镜，准直光束可以聚焦到直径小于1微米，这是衍射极限聚焦点的1.27倍。
