title: Long-range parametric amplification of THz wave with absorption loss exceeding parametric gain.
abstract: Optical parametric mixing is a popular scheme to generate an idler wave at THz frequencies, although the THz wave is often absorbing in the nonlinear optical material. It is widely suggested that the useful material length for co-directional parametric mixing with strong THz-wave absorption is comparable to the THz-wave absorption length in the material. Here we show that, even in the limit of the absorption loss exceeding parametric gain, the THz idler wave can grows monotonically from optical parametric amplification over a much longer distance in a nonlinear optical material until pump depletion. The coherent production of the non-absorbing signal wave can assist the growth of the highly absorbing idler wave. We also show that, for the case of an equal input pump and signal in difference frequency generation, the quick saturation of the THz idler wave predicted from a much simplified and yet popular plane-wave model fails when fast diffraction of the THz wave from the co-propagating optical mixing waves is considered.
authors: HOPE Laboratory, Institute of Photonics Technologies, Hsinchu, Taiwan.
authors: Tsong-Dong
authors: TD
authors: Wang
authors: Yen-Chieh
authors: YC
authors: Huang
authors: Ming-Yun
authors: MY
authors: Chuang
authors: Yen-Hou
authors: YH
authors: Lin
authors: Ching-Han
authors: CH
authors: Lee
authors: Yen-Yin
authors: YY
authors: Lin
authors: Fan-Yi
authors: FY
authors: Lin
authors: Galiya Kh
authors: GKh
authors: Kitaeva
mesh_terms: D000042:Absorption; D000669:Amplifiers, Electronic; D004735:Energy Transfer; D004867:Equipment Design; D019544:Equipment Failure Analysis; D055053:Terahertz Radiation