Rectangular Beam Pumped Raman Microchip Laser for Generating Multiwavelength High‐Order Hermite–Gaussian Lasers and Vortex Lasers

Abstract High‐order Hermite–Gaussian (HG) lasers oscillating at multiple wavelengths are extensively needed for generating vortex lasers carrying orbital angular momentum (OAM), which have wide applications on optical communication, high capacity storage, and high resolution imaging. Off‐axis pumping or off‐axis resonator has been used to generate high‐order HG 0,n lasers, however, low optical efficiency limits practical applications of these lasers. Here, direct generation of multiple wavelength high‐order HG 0,n lasers in a rectangular beam pumped Raman microchip laser constructed with Yb 3+ :Y 3 Al 5 O 12 (Yb:YAG) and yttrium vanadate (YVO 4 ) crystals is demonstrated. The order n of HG 0,n mode lasers can be tuned from 1 to 9. HG 0,n ( n > 3) mode Raman lasers oscillate at multiple wavelengths and shift to longer wavelength with n . The output power is 137 mW for multiwavelength HG 0,9 mode Raman laser when the input pump power is 2.7 W. The optical conversion efficiency is as high as 5.1%. Excellent beam quality with M y 2 close to theoretical values ( M y 2 = 2 n +1) for high‐order HG 0,n lasers has been achieved. Topological charge tunable Laguerre–Gaussian (LG) vortex lasers with high beam quality are generated from HG 0,n mode lasers with an astigmatic mode converter. This work demonstrates that rectangular beam pumping is an effective method for developing efficient multiwavelength high‐order HG 0,n mode Raman lasers.