近年來，兆赫波長光源的產生不論在學術界或是產業界都引起了相當大的注意與關切。到目前為止雖然已有成熟產生兆赫波長光源的方式，但其建構與運轉經費限制了其普遍性。利用非線性光學的基礎，我們可以轉換光源的波長進而產生兆赫波長的光源。
我們利用波長為1064奈米的Q開關雷射為激發雷射光源於鈮酸鋰波導中成功地產生了高效率轉換的兆赫波光源。藉由非同向性相位匹配的條件，當輸入的激發光源的脈衝能量為2.2毫焦耳、脈衝寬度是6奈秒且激發光源形狀為圓形時，於厚度是780微米的鈮酸鋰波導中產生了脈衝能量50微焦耳、脈衝寬度3.4奈秒的訊號。且訊號的頻譜分佈範圍是1070.5奈米到1072.5奈米，其所相對應的兆赫波長範圍從134微米到175微米。在我們的實驗中，厚度780微米的鈮酸鋰波導的轉換效率高達2.24%。從實驗中觀察發現，當改變鈮酸鋰波導的厚度，厚度越薄時所相對應的轉換效率也越高。因此我們推論高轉換效率是由於波導效應所形成的結果。
除此之外，我們也比較圓與橢圓形狀的激發光源對兆赫波輸出能量的影響。當激發光源強度相同時，橢圓形狀的激發光源所產生的兆赫波能量的確大於圓形激發光源的兆赫波能量輸出。這是由於橢圓形狀的激發光源與兆赫波的有效轉換距離大於圓形激發光源的關希。且用橢圓形狀的激發光源，可以在不破壞晶體的情況輸入更多的激發光源能量產生更高的兆赫波能量輸出。

We report the high-efficiency THz parametric generation in 1064-nm pumped lithium niobate waveguides. By using a non-collinearly phase-matched scheme, the measured output siganl energy is 50 □J under 2.2 mJ pumping energy and the signal spectrum is from 1070.5 nm to 1072.5 nm which corresponding to THz wave with 134 □m ~ 175 □m spectrum. The conversion efficiency is as high as 2.24 % with spherical beam pump configuration in a 780-□m-thick lithium niobate. The high conversion is due to the waveguide enhancement. In addition, we compare a cylindrical-beam pumped configuration with a spherical-beam pumped one. The output terahertz-wave energy with the cylindrical-beam pumped configuration is larger than the spherical-beam pumped one under the same pump intensity. The increased aperture also allowed more pump energy into the lithium niobate crystal without any crystal damage.

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