连续运转的太赫兹参量振荡器的实验与理论研究

Teraherz parametric oscillator (TPO) based on stimulated polariton scattering (SPS) could efficiently generate the pulsed, continuous-wave(CW), and quasi-CW terahertz radiation. It has many advantages like operation at room temperature, compactness, good temporal and spatial coherence, continuous tunability. To improve the conversion efficiency and the THz-wave output power of the terahertz parametric source with CW operation, two experimental configurations are researched in this project. One is to place the TPO of the Mg:LiNbO3 crystal within the diode-pumped Nd:YVO4 laser resonator, called the intracavity configuration. The other is the self-TPO configuration based on Nd:MgO:LiNbO3 crystal which combines a gain medium doped Nd3+ and the nonlinear optical frequency conversion of the MgO:LiNbO3 crystal. The self-TPO configuration further shortens the cavity length to improve its conversion efficiency. Besides, the thermal effect of the nonlinear crystal that limits the THz-wave output power would be studied to optimize the parameters of the resonator cavities of the pump and the Stokes lasers. Together with other CW THz-wave sources, the CW-TPO with high conversion efficiency and output power better supports the THz-wave technology and application development. In theory, combining the laser rate equations and the coupled wave equations of the optical nonlinear process, we would build the rate equations describing the CW-TPO with intracavity configuration. The theory would conduct well the design of the CW-TPO.

基于受激电磁耦子散射过程的太赫兹参量振荡器能够有效地产生脉冲、准连续以及连续运转的太赫兹辐射源，具有室温工作、可连续调谐、小型化、时间和空间相干性好等优点。本项目拟将基于MgO:LiNbO3晶体的太赫兹参量振荡器，置于LD泵浦的连续运转激光谐振腔内，获得内腔泵浦的太赫兹参量振荡器结构；基于Nd:MgO:LiNbO3晶体获得自太赫兹参量振荡器，实现小型化，通过实验研究非线性晶体材料的热效应，对泵浦激光和STOKES激光谐振腔参数进行最优化设计，最终获得高转换效率、高输出功率、连续运转的太赫兹辐射源，与其他类型连续运转的太赫兹辐射源形成优势互补。在理论上，结合描述激光运转的速率方程和太赫兹参量过程的耦合波方程，建立包含泵浦激光、STOKES激光和太赫兹波空间分布的速率方程组来描述内腔泵浦的连续太赫兹参量振荡器的运转过程，为该类太赫兹源的设计提供规律性依据。

基于受激电磁耦子散射过程的太赫兹参量振荡器能够有效地产生脉冲、准连续以及连续运转的太赫兹辐射源，具有室温工作、可连续调谐、小型化、时间和空间相干性好等优点。本项目基于MgO:LiNbO3晶体的太赫兹参量振荡器，置于LD泵浦的连续运转激光谐振腔内，获得内腔泵浦的太赫兹参量振荡器结构；通过对泵浦激光和STOKES激光谐振腔参数进行最优化设计，最终获得高转换效率、高输出功率、准连续或者连续运转的太赫兹辐射源。端面泵浦的准连续太赫兹参量振荡源的输出功率约为8.2 μW，光光转化效率为1.17×10-6，调谐范围为1.31 THz到2.70 THz；侧面泵浦的准连续太赫兹参量振荡源的输出功率约为123 μW，光光转化效率为1.255×10-6，调谐范围为1.3 THz至2.8 THz；侧面泵浦的连续太赫兹参量振荡源的输出功率约为51 μW，光光转化效率为0.52×10-6，与其他类型连续运转的太赫兹辐射源形成优势互补。在理论上，结合描述激光运转的速率方程和太赫兹参量过程的耦合波方程，建立包含泵浦激光、STOKES激光和太赫兹波空间分布的速率方程组来描述内腔泵浦的连续太赫兹参量振荡器的运转过程，为该类太赫兹源的设计提供规律性依据。