We have been using the principles of injection-seeded terahertz parametric generation (TPG) to develop the terahertz parametric amplifier (TPA) since 2014. Although we previously achieved amplification of 55 dB at 1.6 THz, amplification of low-frequency terahertz waves (≤1 THz) or ultraweak inputs was difficult, because broadband terahertz waves (spontaneous TPG) were generated and interfered with amplification. Thus, we herein present a new technique that divides terahertz-wave amplification into two steps: preamplification and main amplification. In this configuration, the terahertz wave is upconverted to a near-infrared (NIR) beam. Then, the noise is removed under the NIR condition and converted again to terahertz waves by the main amplifier. This two-stage TPA affords an extremely high amplification factor (up to six-billion-fold; 98 dB) for an ultraweak input of 500 zJ (zJ = 10−21 J). This is the first amplifier that has such a high gain for sub-aJ order input in the terahertz region.

中文翻译：

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通过两级太赫兹参量放大器实现 60 亿倍放大

自 2014 年以来，我们一直利用注入种子太赫兹参数生成 (TPG) 的原理开发太赫兹参数放大器 (TPA)。虽然我们之前在 1.6 THz 下实现了 55 dB 的放大，但低频太赫兹波（≤太赫兹）或超弱输入是困难的，因为宽带太赫兹波（自发 TPG）会产生并干扰放大。因此，我们在此提出一种新技术，将太赫兹波放大分为两个步骤：前置放大和主放大。在这种配置中，太赫兹波被上变频为近红外 (NIR) 光束。然后，噪声在近红外条件下被去除，并由主放大器再次转换为太赫兹波。这种两级 TPA 提供了极高的放大系数（高达 60 亿倍；98 dB) 对于 500 zJ (zJ = 10−21 J) 的超弱输入。这是第一个在太赫兹区域对亚 aJ 阶输入具有如此高增益的放大器。