耗散孤子光参量振荡器研究

Mid-infrared ultrashort and ultra-intense laser have attracted wide interest of researchers in recent years due to their tremendous prospect of application. Synchronously-pumped optical parametric oscillator is one of the universe techniques for generating mid-infrared ultrashort pulses, however, traditional optical parametric oscillator only possesses the functionality of frequency conversion and it cannot significantly promote the performance of mid-infrared ultrashort pulses (pulse duration, peak power, etc). In this project we propose a synchronously-pumped dissipative soliton optical parametric oscillator technique. Through controlling the intracavity dispersion, nonlinearity, and gain, the dissipative soliton optical parametric oscillator can generate giant linear-chirped mid-infrared pulses under pumping of high-energy picosecond pulses, and then mid-infrared femtosecond pulses and even few-cycle mid-infrared pulses can be obtained by compensating for the dispersion outside of the cavity, which largely shortens the pulse duration and promotes the peak power of mid-infrared pulses. The proposed technique provides a novel ways for generation of high-repetition-rate, high-peak-power, ultrashort mid-infrared pulses, and it can significantly promote the performance of current ultrashort pulse optical parametric oscillator, and will open new applications of mid-infrared ultrashort and ultra-intense laser.

中红外超短超强激光由于巨大的应用前景近年来吸引了科研人员的广泛兴趣。同步泵浦的光参量振荡器是产生中红外超短脉冲的通用技术之一，然而传统的光参量振荡器只有频率转换功能，难于显著提升中红外超短脉冲的性能（脉宽、峰值功率等）。该项目我们提出了一种同步泵浦的耗散孤子光参量振荡器技术，通过控制腔内色散、非线性以及增益大小，在高能皮秒脉冲泵浦下该耗散孤子光参量振荡器可产生巨线性啁啾的中红外脉冲，通过腔外色散补偿就可得到超短的中红外飞秒脉冲甚至周期量级中红外飞秒脉冲，可大幅度缩短脉宽和提升中红外脉冲峰值功率。提出的技术为产生高重频、高峰值功率、极短脉宽的中红外激光提供了一条全新的技术途径，可显著提升现有超短脉冲光参量振荡器的性能，将可能打开新的中红外超短超强激光的应用。

中红外超短脉冲激光由于在光谱学、非线性显微成像、强场物理等方面的重大应用前景而受到广泛关注。同步泵浦的光参量振荡器是产生中红外超短脉冲的通用技术，然而传统的光参量振荡器只有频率转换功能，难于显著提升中红外超短脉冲的性能（脉宽、峰值功率等）。本项目我们提出了一种可大幅提升中红外超短脉冲性能的新型光参量振荡器——耗散孤子光参量振荡器。通过控制光参量振荡器中色散、非线性相移、增益和非线性损耗之间的平衡，该类光参量振荡器可以产生宽带的近线性啁啾脉冲，通过腔外色散补偿可以实现超短的中红外脉宽和超高的峰值功率。我们建立了该类耗散孤子光参量振荡器的理论模型和数值模拟程序，揭示了泵浦脉冲的时间滤波效应是耗散孤子形成的关键。我们实验演示了在800fs近红外脉冲同步泵浦的光参量振荡器中，产生了近200nm带宽的1.11ps稳定耗散孤子，通过腔外色散补偿实现了88fs的2.3μm中红外飞秒脉冲产生，演示了相比传统光参量振荡器技术超过一个量级的中红外峰值功率提升。另外，我们揭示了非线性相移和色散同号是光参量振荡器中耗散孤子形成的基本条件，通过级联非线性提供符号可控的非线性相移，我们在正色散和负色散腔中分别实现了耗散孤子，首次将耗散孤子产生拓展到负色散区域。特别是，我们探索了耗散孤子光参量振荡器技术产生少周期中红外脉冲的可行性，理论证实通过ZnGeP2耗散孤子光参量振荡器和腔外色散补偿在10μm波长可以产生1.5个光周期的极短长波中红外脉冲。本项目提出和验证的耗散孤子光参量振荡器技术为高重频、极短脉宽、超高峰值功率中红外脉冲产生提供了一条全新的技术途径，将推动中红外超短脉冲激光源的发展，使得中红外光谱学、中红外频率梳、中红外强场物理等应用领域受益。