The frequency degeneracy range of transverse mode in an off-axis end-pumped solid-state lasers

Abstract The degenerate phenomena of transverse modal frequency in an off-axis end-pumped solid-state lasers was researched based on a semi-confocal cavity. Experimental results showed that at the large off-axis distance the transverse mode pattern changed from the Hermite-Gaussian mode to the geometric mode and finally back to the Hermite-Gaussian mode as cavity length varied. At the large off-axis distance, the degeneracy range of transverse mode patterns was a cavity length to mirrors radius ratio from 0.4958 to 0.5092 and the frequency degeneracy range was a cavity length to mirrors radius ratio from 0.4974 to 0.5025. The degeneracy range by observing beating frequency changes was more accurate and more useful than the method by comparing the transverse pattern changes. Furthermore, it was found that the off-axis pumping did not significantly alter the degeneracy position and range.