非線性混頻技術已經成為一個有效低能量高同調兆赫波的產生方式，週期性極化晶格反轉鈮酸鋰晶體提供補償波向量使可達成同向性的相位匹配，因此成為大多數非線性混頻技術的核心產生物質。在這篇論文之中，我們主要以共線相位匹配方式的兆赫波參數產生器作為核心探討課題。首先，我們藉由能量為150微焦耳、波長為532奈米的主動Q調制雷射和能量為60微焦耳、波長為1064奈米的被動Q調制雷射，激發近6公分長、780微米厚的週期性極化晶格反轉鈮酸鋰波導，在準相位匹配的條件下，我們成功地建立高轉換效率同相性相位匹配機制的兆赫波參數產生器。在此同向兆赫波參數產生器中，我們所使用的週期性極化晶格反轉晶體的晶格週期分別是71.5毫米跟67毫米，而它們分別對應到使用532奈米和1064奈米雷射激發，而我們量測到對應的兆赫波波長分別為80微米和330微米。因同向性的相位匹配有較長的有效增益長度，以及此780微米厚鈮酸鋰晶體中之兆赫波波導效應，使用能量為100微焦耳、波長為532奈米的雷射激發所產生的80微米兆赫波，可以使用壓電偵測器量得，其能量可以達到次奈米焦耳。更進一步地，由成功建立正向兆赫產生器的經驗，我們嘗試地完成約四十年未完成的實驗—背向光參數震盪器。藉由波長為532奈米和能量為250微焦耳的主動Q調制雷射激發近4公分長、780微米厚、44和32微米晶格週期的週期性極化晶格反轉鈮酸鋰波導。目前由觀測閒置波的能量，我們得到背向參數震盪器的門檻能量約為30微焦耳。在同樣的實驗架構之下，我們同時藉由激發波長為1064奈米的雷射進入厚度為500微米跟1000微米的週期性極化晶格反轉鈮酸鋰晶體中，我們從觀察閒置波的光譜確定了在此些厚度的鈮酸鋰晶體中兆赫波波導的特性。

Terahertz (THz)-wave’s generation and detection have gained increasing interests from fundamental and applied perspectives. Nonlinear wavelength mixing has been one of the most effective techniques to generate low-power coherent THz radiations. Recently, periodically poled lithium niobate (PPLN) has become the nonlinear-optical material of the choice, which provides the compensating wave-vector to achieve the collinear phase-matching condition.

We first report high-efficiency, collinearly phase-matched terahertz-wave parametric generation (TPG) in a 6-cm long, 780-□m thick PPLN waveguides pumped by a ~150 □J/pulse actively Q-switched laser at 532-nm wavelength and by a ~60 □J/pulse passively Q-switched Nd:YAG laser at 1064-nm wavelength. We measured 80-□m and 330-□m terahertz wavelengths from the 532-nm and 1064-nm pumped PPLN crystals with domain periods of 71.5 □m and 67 □m, respectively. Due to the long gain length and the waveguide-mode confinement, sub-nJ terahertz radiation at 80-□m wavelength was detected by a pyrodetector with 100-□J pump energy at the 532-nm wavelength. Furthermore, we try to accomplish the experiment of backward terahertz-wave parametric oscillation (TPO) in a 4-cm long and 780-□m thick PPLN waveguides having a domain inversion period of 44-□m and 32-□m pumped by a ~250 □J/pulse actively Q-switched laser at a 532-nm wavelength. From the observed signal output, the threshold energy of the backward oscillation was ~30 □J. The waveguide confinement of the THz wave was confirmed by comparing the signal spectrum of 1064-nm pumped PPLN crystals with 500-□m and 1000-□m thickness.

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