Sharma Varun, Kumar S Chaitanya, Aadhi A, Ye H, Samanta G K, Ebrahim-Zadeh M
Photonic Sciences Lab., Physical Research Laboratory, Navarangpura, Ahmedabad, 380009, Gujarat, India.
Indian Institute of Technology-Gandhinagar, Ahmedabad, 382424, Gujarat, India.
Sci Rep. 2019 Jul 3;9(1):9578. doi: 10.1038/s41598-019-46016-y.
Vector-vortex beams, having both phase and polarization singularities, are of great interest for a variety of applications. Generally, such beams are produced through systematic control of phase and polarization of the laser beam, typically external to the source. However, efforts have been made to generate vector-vortex beams directly from the laser source. Given the operation of the laser at discrete wavelengths, vector-vortices are generated with limited or no wavelength tunability. Here, we report an experimental scheme for the direct generation of vector-vortex beams. Exploiting the orbital angular momentum conservation and the broad wavelength versatility of an optical parametric oscillator, we systematically control the polarization of the resonant beam using a pair of intracavity quarter-wave plates to generate coherent vector-vortex beam tunable across 964-990 nm, with output states represented on the higher-order Poincaré sphere. The generic experimental scheme paves the way for new sources of structured beams in any wavelength range across the optical spectrum and in all time-scales from continuous-wave to ultrafast regime.
矢量涡旋光束同时具有相位奇点和偏振奇点，在各种应用中备受关注。通常，此类光束是通过对激光束的相位和偏振进行系统控制产生的，这通常在光源外部进行。然而，人们一直在努力直接从激光源产生矢量涡旋光束。鉴于激光在离散波长下运行，所产生的矢量涡旋具有有限的波长可调性或根本没有波长可调性。在此，我们报告一种直接产生矢量涡旋光束的实验方案。利用光学参量振荡器的轨道角动量守恒和宽波长通用性，我们使用一对腔内四分之一波片系统地控制谐振光束的偏振，以产生在964 - 990纳米范围内可调谐的相干矢量涡旋光束，其输出状态由高阶庞加莱球表示。这一通用实验方案为在整个光谱的任何波长范围内以及从连续波到超快 regime 的所有时间尺度上产生新型结构化光束源铺平了道路。
