Direct generation of orthogonally polarized dual-wavelength orbital Poincaré modes at 639 nm and 721 nm in a blue-diode pumped Pr:YLF laser

Abstract

We report on the first, to the best of our knowledge, direct generation of orthogonally polarized dual-wavelength laser with orbital Poincaré (OP) modes at 639 nm and 721 nm in a blue-diode pumped Pr:YLF laser. Beyond the single-wavelength emission, dual-wavelength laser can be approached by adjusting the tilt angle of the output mirror in the critical cavity. In addition, either monochromatic or bi-chromatic orbital Poincaré modes, including Hermite-Gaussian (HG) modes, Laguerre-Gaussian (LG) modes and Hermite-Laguerre Gaussian (HLG) modes can be directly generated by simple off-axis pump scheme and displacement of the output mirror. Moreover, hybrid eigenmodes with S-shape beam profile resulting from dual singularities at the wavefront are observed, as well as the mode switching along with the increase of the pump power. Meanwhile, these composite modes are replicated by simulations using the coherent superposition of higher order HG modes. This work may shed new light on the dual-wavelength laser at visible regime with various modes for potential applications.