1.5 μm passively Q-switched self frequency conversion optical parametric oscillator based on Nd3+ doped MgO:PPLN with the multi-focus end-face coupling pumping mode

Abstract

A 1.5 μm passively Q-switched self frequency conversion optical parametric oscillator based on Nd3+ doped MgO:PPLN with the multi-focus end-face coupling pumping mode is reported. The reason for the generation of dual-wavelength fundamental frequency laser is explained by Nd:MgO:PPLN laser characteristics and energy level theory, and a multi-focus pumping thermal model is established to numerically simulate the temperature field distribution under different pumping injection modes. Compared with the traditional single-focus pumping mode, the multi-focus coupling pumping mode effectively disperses the thermal effect of the Nd:MgO:PPLN crystal, the oscillation of the σ-polarized 1093 nm laser is suppressed, the single-wavelength output of the π-polarized 1084 nm laser is realized. Thereby the more efficient 1514 nm signal light is obtained. In the experiment, the 1514 nm signal light with an average output power of 183 mW is obtained when the repetition frequency is 5.4 kHz, the pulse width is 6.8 ns and the pulse energy is 34 μJ in the double-focus pumping mode. In the triple-focus pumping mode, the 1514 nm signal light with an average output power of 165 mW is obtained when the repetition frequency is 5.6 kHz, the pulse width is 7.2 ns and the pulse energy is 30 μJ. Overall evaluation of the experimental effects of the two kinds of pumping modes shows that the double-focus pumping mode is superior to the triple-focus pumping mode.