We report a bunch-mode-operated, wavelength-tunable, temperature-insensitive high power, mid-infrared (MIR) laser based on difference frequency generation (DFG) in a periodically poled Magneoisum-oxide doped Lithium Niobate (PPMgLN) chip. Two synchronized fiber lasers each with master oscillator power amplifier (MOPA) structures are utilized as pump and signal sources for the DFG. The pump laser is seeded by a mode-locked Yb fiber laser around 1030 nm with fundamental repetition rate of 16.32 MHz and pulse duration of 8.5 ps. Each pulse of the pump seed is multiplied by a factor of 16, forming the pulse bunch, and then amplified to 27.8 W. A super-luminescent light emitting diode (SLED) around 1580 nm is triggered by the first pulses of the pump bunch and adopted as the signal seed, which is amplified to 4 W afterwards. The pulse duration and spectral bandwidth of the signal are ~ 5 ns and 50 nm, respectively, covering the total duration of the pump bunch in the time domain and signal wavelength tuning range in the spectral domain, respectively, enabling wavelength-tuning DFG with temperature-insensitive power scaling. High power pulse bunch MIR laser can always be realized within the crystal temperature range from 25 to 95 °C with corresponding idler wavelength from 3.03 μm to 2.84 μm. The highest idler power of 4.6 W is achieved at 3.0 μm with pump-to-idler conversion efficiency of ~ 16.5%. It is believed that such a bunch-mode-operated, mid-infrared ps laser source with high output power within the whole temperature-wavelength tuning range are of great value to the evaluation of wavelength dependent laser bio-ablation.

我们报告了基于周期极化极化氧化镁掺杂的铌酸锂（PPMgLN）芯片中基于差频产生（DFG）的束模式操作，波长可调，对温度不敏感的高功率中红外（MIR）激光器。两个同步光纤激光器分别具有主振荡器功率放大器（MOPA）结构，用作DFG的泵浦和信号源。泵浦激光器由锁模Yb光纤激光器在1030 nm附近播种，其基本重复频率为16.32 MHz，脉冲持续时间为8.5 ps。泵浦种子的每个脉冲乘以16的倍数，形成脉冲束，然后放大到27.8W。大约1580 nm的超发光二极管（SLED）由泵浦束的第一个脉冲触发，并且用作信号种子，然后放大到4W。信号的脉冲持续时间和光谱带宽分别为〜5 ns和50 nm，分别覆盖了时域中泵浦束的总持续时间和光谱域中信号波长的调谐范围，从而实现了随温度变化的DFG波长-不敏感的功率缩放。高功率脉冲束MIR激光器始终可以在25至95°C的晶体温度范围内实现，相应的惰轮波长为3.03μm至2.84μm。3.0μm时可实现4.6 W的最高惰轮功率，泵至惰轮的转换效率约为16.5％。可以相信，这种在整个温度-波长调谐范围内具有高输出功率的束模式操作的中红外ps激光源，对于评估与波长相关的激光生物消融具有重要价值。