ABSTRACT
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.
ABSTRACT
In this paper, we present a modular design configuration to side-pump an Nd:YAG rod of a diode-pumped high-power CW laser. Independent modules in the form of discs are loaded with three-diode linear bar arrays at 120° with respect to each other and are assembled along the length of the rod. By keeping successive discs at three different angular separations (the minimum, intermediate, and maximum), helical, 60° rotated, and linear geometries, respectively, were created. Parameters like thermal lensing, fluorescence profile, laser beam profile, and beam quality factor (M2) were studied to compare the performances of different geometries. The results indicate that the 60° rotated configuration provides the best performance when compared with rest of the schemes. To the best of our knowledge, this is the first time that such novel modular-type pump geometries with a provision for the angular separation of pump diodes have been tried.
