波長可調且窄頻的兆赫波可以用於化學指紋分子識別相關的光學量測，兆赫波參量放大器可以在室溫下產生窄頻的兆赫波。本論文主要探討在進行兆赫波參量放大器時所需設備之原理及增強兆赫波之方法。本實驗使用波長為1064 nm、脈衝寬度為10皮秒且重覆率為54 MHz的鎖模雷射進行放大，經過Nd:YAG再生放大器放大後得到重覆率為10 Hz且具有700 μJ能量的脈衝，這些高能量的脈衝便成為兆赫波參量放大器的泵浦光源。本實驗使用厚度1 mm的KTP作為非線性波長轉換晶體，在兆赫波參量產生的狀況下，由於受激電磁耦子散射，會產生1086 nm波段的Stokes訊號。為了達到波長可調與窄頻的目的，我們架設了波長可調的外腔二極體雷射作為種子光源。此外，還使用了波前傾斜技術來增加轉換效率。最終產生了脈衝能量78 μJ的一階Stokes波和34 μJ的二階Stokes波。

It is generally believed that a wavelength-tunable and narrow-band terahertz wave can perform optical inspections such as chemical fingerprint detections. A terahertz parametric amplifier can generate a narrow-band terahertz wave at room temperature. My thesis will firstly discuss how a terahertz parametric amplifier (TPA) is driven by a wavefront-tilted pump laser. A mode-locked laser, which has a 1064-nm wavelength, 10-ps pulsewidth, and 54-MHz repetition rate, is first amplified by a regenerative amplifier. The amplified pulse has 700 μJ energy, and repeats at a 10-Hz rate. The high energy pulse is a pump source for TPA. The crystal used is KTP with a thickness of 1 mm. When performing terahertz parametric generation via stimulated polariton scattering, a Stokes wave with 1086 nm wavelength will be generated. To achieve narrow band and tunable wavelength, an external cavity diode laser was built as a seed source for TPA. Additionally, the wavefront of the pump wave was tilted so as to achieve group velocity matching and therefore improve the efficiency. As the result indicates, the first-order Stokes wave with 78 μJ energy can be generated and second-order Stokes waves with 36 μJ energy from the TPA crystal.

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