同步脉冲诱导的高功率中红外差频产生技术(特邀)

High-power mid-infrared difference-frequency generation based on synchronous pulse induction(Invited)

提出并实验探究了基于同步脉冲诱导的中红外差频产生技术,利用高速光电探测器将泵浦光脉冲转换为超短电信号,使其驱动宽带的幅度调制器,作用于可调谐连续激光器上,从而实现双色脉冲的稳定时域同步。利用了同步脉冲诱导的非线性差频过程,有效降低了光参量下转换的泵浦阈值,能够获得瓦量级的中红外超短脉冲输出,最大泵浦光转换效率达60%,且中心波长在3 000~3 175 nm范围内可调谐。得益于全保偏光纤架构,平均功率的不稳定度(STD/MEAN)在1 h内低至0.07%,展现了优异的长期稳定性。此外,该方案利用光-电-光高速调制实现高精度脉冲同步,免除了复杂的反馈电路,具有结构简单、即插即用、鲁棒性强的特点,为拓展中红外光源在野外的应用奠定了基础。

A mid-infrared(MIR) difference-frequency generation(DFG) technique based on the synchronous pulse induction was proposed and implemented, where a high-speed photodiode detector was used to convert the pump optical pulse into an ultrashort electrical signal for driving a high-bandwidth amplitude modulator on a tunable continuous-wave laser, thus leading to the stable timing synchronization between the dual-color pulses.The nonlinear DFG process with synchronous pulse induction was utilized to effectively reduce the pump threshold for the optical parametric down-conversion. Consequently, watt-level MIR ultrashort pulses could be generated with a maximum pump conversion efficiency up to 60%. The central wavelength could be tuned from 3 000 to 3 175 nm. Thanks to the all-polarization-maintaining fiber architecture, the instability(STD/MEAN) of the average power was as low as 0.07% in one hour, exhibiting a superior long-term stability. Additionally, the optical-electrical-optical conversion was used to implement the high-precision pulse synchronization with the presented scheme, which eliminated the requirement for the complex feedback circuit. The system was thus featured with simple structure, plug-in operation, and strong robustness, which would pave the way to promoting the MIR light source in field applications.