Structured Light Fields with 2D Tunable Indices Generated in a Raman Microchip Laser

Abstract

Structured light fields in the form of Hermite-Gaussian modes with 2D tunable indices of m and n (HG_m,n), and optical vortices in the form of Laguerre-Gaussian modes with radial index p and azimuthal index l (LG_p,l) are extremely needed for applications on optical communications, optical trapping, and quantum information processing. Here, high-order HG_m,n modes and LG_p,l optical vortices with 2D tunable indices are generated in a gain-manipulated Yb:YAG/YVO₄ Raman microchip laser (RML). The gain distribution is manipulated by controlling the separation between Yb:YAG crystal and the focus spot of the y-axis of the laser diode (Δz). HG_m,n modes with 2D tunable indices of m up to 14 and n up to 2 are generated in Yb:YAG/YVO₄ RML by setting Δz = −0.5, −4.1, and −6.6 mm. The power of HG_14,0, HG_7,1, and HG_6,2 mode lasers are 0.49, 0.31, and 0.34 W under pump power of 3.1 W, and corresponding optical efficiencies are 11%, 7%, and 7.7%. LG_p,l optical vortices with p = 0, 1, 2, and l up to 14 are converted from HG_m,n mode lasers with a conversion efficiency of over 90%. High beam quality HG_m,n modes, and LG_p,l optical vortices with 2D tunable indices oscillating at Stokes wavelengths dramatically extend their applications.