Modular pump head design of diffused, metal, and hybrid pump geometry for diode-side-pumped high power Nd:YAG laser

In this paper, we present a comparative study on pump heads for a high power diode-side-pumped Nd:YAG laser. The pump head is a modular type, which is in the form of discs, with each disc holding three pump diodes kept at 120° with respect to each other. Unabsorbed pump light from the active medium is reflected by reflectors mounted adjacent to the pump diodes. The performance of a high power pump head made of modular discs mounted with specular or diffused type reflectors was studied. Hybrid pump geometry was also investigated, where the pump head is made up of discs loaded with metal and diffused reflectors, alternately. The discs are loaded around the active medium in such a way that successive discs are rotated by sixty degrees with respect to each other. Fluorescence profiles, thermal lensing, laser output power, and M² values were studied for pump heads made up of metal, diffused, and hybrid type reflectors. All of the pump heads were studied for three different resonator lengths to maximize the output power with the best beam quality. The experimental results show that the diffused reflector-based geometry in a sixty degree rotated configuration produced the maximum output power and best beam quality in terms of the M² value.