Q-switched quasi-concentric laser resonator with line-shaped end-pumping profile: power-insensitive operating point and symmetrized TEM00 output

Abstract

We put forward a quasi-concentric laser resonator configuration employing a line-shaped end-pumping profile (QRLE). A thermal lensing modeling of the QRLE is developed, including the quartic phase deformation and the dependence of the thermal focal power on the TEM₀₀ mode size at the thermal lens. Based on the calculation, we found that the dynamic operating point of the QRLE depends on both the resonator condition and the thermal effect condition. Furthermore, we predicted that the operating point in the subcritical region is insensitive to power fluctuation, i.e., the QRLE with extremely short cavity length is capable of stable operation. The validity of our prediction was well confirmed by theoretical modeling and experimental realization. Compared to conventional resonator designs, the QRLE resonator design produces the fundamental mode output with an LD bar instead of the fiber-coupled pump source and realizes good stability with short cavity length, demonstrating a clear advantage of both low cost and compactness. Based on the QRLE configuration, we produced >12 W pulsed TEM₀₀ output, with the repetition rate of 30 kHz and optical-optical efficiency of 27%. The laser output mode is elaborately symmetrized in two directions in terms of beam quality, waist radius, and waist position.