Engineered quasi-phase-matching in a periodically poled nonlinear crystal has enabled backward optical parametric oscillators, where a pump photon is down-converted to counterpropagating signal and idler photons without an optical cavity. Here, we demonstrate an injection-seeded backward terahertz-wave parametric oscillator (BW-TPO) based on a slant-strip-type periodically poled lithium niobate crystal. A continuous-wave single-frequency laser is used in the BW-TPO pumped by sub-nanosecond 1064.4-nm pulses to provide an injection seed beam for the forward-propagating idler wavelength at 1065.7 nm, resulting in over a 1000-fold enhancement in backward-propagating 0.335-THz output energy, a 63% reduction of the oscillation threshold, and a quantum conversion efficiency as high as 47%. Thanks to the unique advantage of cavity-less oscillation, these improvements and stable operation in the BW-TPO are achieved without any stabilization control of either seed or oscillation modes. Our results show that such an injection-seeded BW-TPO is promising as a compact, efficient, and robust THz-wave source for a wide variety of applications.

中文翻译：

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注入种子反向太赫兹波参量振荡器

在周期性极化的非线性晶体中设计的准相位匹配已使能反向光参量振荡器，其中泵浦光子被下变频为反向传播的信号和空子光子，而没有光腔。在这里，我们演示了基于斜条型周期极化铌酸锂晶体的注入种子反向太赫兹波参数振荡器（BW-TPO）。在亚纳秒1064.4 nm脉冲泵浦的BW-TPO中使用了连续波单频激光器，以为1065.7 nm的正向传播惰轮波长提供注入种子束，从而使倍频增强了1000倍。向后传播的0.335 THz输出能量，振荡阈值降低63％，量子转换效率高达47％。由于无腔振荡的独特优势，这些改进和BW-TPO的稳定运行无需对种子模式或振荡模式进行任何稳定控制即可实现。我们的结果表明，这种注入种子的BW-TPO作为一种紧凑，高效且坚固的太赫兹波源，有望在多种应用中使用。