优化级联光学参量振荡产生高功率太赫兹波的研究(特邀)

High Power Terahertz Wave Generated by Optimizing Cascaded Optical Parametric Oscillation(Invited)

提出了一种在光学参量振荡器中基于级联光学差频在周期极化铌酸锂晶体中产生高效太赫兹(THz)波的方法。通过优化谐振腔参数,各阶级联Stokes光子在谐振腔内往返振荡,而各阶anti-Stokes光子只能在谐振腔内穿过一次。结合优化差频技术,各阶Stokes光子在谐振腔内每循环一次,级联光的能量向高阶Stokes光子转移一次,经多次重复转移,绝大部分泵浦光子被转移到高阶Stokes光,达到在增强级联Stokes过程的同时抑制级联anti-Stokes过程的效果。在工作温度为100 K,泵浦光强度为10 MW/cm^(2)、信号光强度为0.01 MW/cm^(2)时,THz波的能量转换效率达到21.2%。该转换效率超过了Manley-Rowe关系限制,为产生高效率的脉冲、准连续、连续THz波提供了优化方案。

A scheme to generate high-efficiency terahertz(THz) wave based on cascaded difference frequency generated in a periodic polarized lithium niobate(PPLN) crystal with an optical parametric oscillator is presented.By optimizing the reflectivity of the resonator mirror, Stokes photons oscillate in the cavity, while anti Stokes photons pass through the cavity only once. All the Stokes photons propagate from the left side of the cavity to the right, which ensures that all the Stokes photons pass through the PPLN crystal in one direction. Every time the Stokes photons oscillate in the cavity, the photons of the pump waves are transferred to the Stokes photons. The Stokes processes are enhanced and the anti-Stokes processes are depressed simultaneously. The energy conversion efficiency from pump wave to THz wave reaches 21.2% with pump wave intensity of 10 MW/cm^(2) and signal wave intensity of 0.01 MW/cm^(2) at 100 K operation temperature. The above efficiency exceeds the Manley-Rowe relation,which provides an optimal scheme for generation of high efficient pulse, quasi-continuous, continuous THz waves.