Decentered Gaussian Beam Pumped Highly Efficient Passively Q-Switched Microchip Laser for Controllable High-Order Transverse Modes

Abstract

Versatile controllable high-order transverse laser modes have been generated in a decentered Gaussian beam (DGB) pumped Cr4+:YAG passively Q-switched (PQS) Nd:YAG microchip laser. The DGB has been formed by offsetting collimating lens away from the propagation direction of the pump light. Effects of the collimating lens offset distance on the beam profile and tilting angle of the DGB have been investigated experimentally and theoretically. A highly efficient and high repetition rate Laguerre–Gaussian (LG) mode PQS microchip laser is achieved when the ordinary Gaussian beam is used as the pump source. The Ince–Gaussian (IG) mode and Hermite–Gaussian (HG) mode lasers are obtained when the DGB is applied as the pump source. The IG mode laser is changed to an HG mode laser by increasing the offset distance of the collimating lens. Optical efficiencies above 41% respective to the absorbed pump power have been obtained in the DGB pumped LG and IG mode PQS Nd:YAG microchip laser. The nanosecond pulse width and peak power of over 4 kW has been achieved in DGB pumped PQS Nd:YAG microchip lasers for various high-order transverse modes. Our works on the DGB pumped PQS microchip laser for high-order transverse modes provide an effective and simple method for designing highly efficient, controllable LG, IG, and HG mode solid-state lasers.