Generation of controllable Ince – Gaussian modes in a passively Q-switched microchip laser under truncated decentred Gaussian beam pumping

Abstract

We report a passively Q-switched (PQS) Nd : YAG/Cr4+: YAG microchip laser pumped by a truncated decentred Gaussian beam for controllable Ince – Gaussian (IG) mode generation. IGe(n, n) modes (n = 0, …, 4) are obtained experimentally by choosing the appropriate truncation parameter, which is defined as a ratio of the radius of the aperture to the beam waist. The IGe(4, 4) mode is produced in the PQS Nd : YAG/Cr4+: YAG microchip laser under decentred Gaussian beam pumping at a pump power of 2.6 W, the mode selection being achieved by reducing the truncation parameter. The threshold pump powers for different IGe(n, n) modes are theoretically calculated to illustrate the mode selection process. The pulsed IGe(n, n) (n ≥ 1) mode generation with a peak power exceeding 1 kW and a nanosecond pulse width is obtained in the PQS microchip laser, which is a potential laser source for forming flexible vortex arrays for optical tweezers.