Al-Attili Abdelrahman Zaher, Burt Daniel, Li Zuo, Higashitarumizu Naoki, Gardes Frederic, Ishikawa Yasuhiko, Saito Shinichi
Sustainable Electronic Technologies, Electronics and Computer Science, University of Southampton, Southampton, SO17 1BJ, UK.
Electrical Engineering Department, School of Engineering Technology, Al Hussein Technical University, 11831, Amman, Jordan.
Sci Rep. 2022 May 6;12(1):7465. doi: 10.1038/s41598-022-11245-1.
Group IV light sources with vertical emission and non-zero orbital-angular momentum (OAM) promise to unlock many novel applications. In this report, we demonstrate cylindrically symmetrical germanium micro-gear cavities, fabricated by etching a grating around the circumference of standard micro-disks, with periods ranging from 14 to 22. Photoluminescence (PL) measurements were done to identify the confined whispering-gallery modes (WGM). Finite-difference time-domain (FDTD) simulations were conducted to map the resonant modes to their modal profiles and characteristics. Vertical emission of WGMs with non-zero OAM was demonstrated, with a clear dependence of the OAM order ([Formula: see text]) on the WGM azimuthal order and the number of micro-gear grating periods. As the chirality, or the direction of rotation, is not controlled in a symmetrical cavity, we propose introducing staircase or triangular-shaped gear periods resulting in an asymmetry. By choosing the diameter, number of periods, and the asymmetrical direction of the gear-teeth, it is possible to generate OAM signals with certain wavelength, OAM order and chirality.
具有垂直发射和非零轨道角动量（OAM）的IV族光源有望开启许多新颖的应用。在本报告中，我们展示了通过在标准微盘的圆周周围蚀刻光栅制造的圆柱形对称锗微齿轮腔，其周期范围为14至22。进行了光致发光（PL）测量以识别受限的回音壁模式（WGM）。进行了有限差分时域（FDTD）模拟，以将共振模式映射到其模式轮廓和特性。展示了具有非零OAM的WGM的垂直发射，OAM阶数（[公式：见正文]）明显依赖于WGM方位角阶数和微齿轮光栅周期数。由于在对称腔中未控制手性或旋转方向，我们建议引入阶梯形或三角形齿轮周期以产生不对称性。通过选择直径、周期数和齿轮齿的不对称方向，可以生成具有特定波长、OAM阶数和手性的OAM信号。
