Inner-cavity generation of mid-infrared optical vortex arrays from an Er:CaF2 laser

Abstract

We demonstrate the inner-cavity generation of mid-infrared optical vortex arrays from an Er:CaF2 laser. By shifting the position of the defect point on the input mirror, multiple transverse modes simultaneously oscillated in the cavity and constituted vortex arrays by transverse mode locking. The maximum output power of TEM00 mode could reach 440 mW with a low threshold of 463 mW. The maximum output powers of LG0,1, the 1 × 2 and the 2 × 2 vortex arrays were 254 mW, 131 mW, and 117 mW, respectively. The chirality of the vortex arrays could be reversed by slightly adjusting the geometric loss of the cavity. The light intensity distribution, interference, and phase distribution were simulated and they were in good accordance with the experimental results. This method provides deep insight into inner-cavity generation of vortex arrays in mid-infrared regime.