飛秒光參數放大器及其特性研究

Abstract

利用在晶體內產生的二階非線性機制(光參數放大, OPA)去架設一套波長可調的雷射，並且利用頻率解析光時閘(FROG)的技術去量測脈衝的特性。藉由調整BBO的角度，滿足相位匹配的波長就會被放大，而範圍從1141到1524奈米；而同時另一道因滿足能量守恆的波長也會被產生出來，範圍從1684到2677奈米。輸出光源的平均功率大約有數十個mW，而脈衝寬度大約50飛秒。

另一部份，我們參考利用多道光源去做光參數放大以及非共線光參數放大，另外還引進single-shot的幾何結構去做超寬頻的光參數放大。為了了解這些變數在這樣的過程中有著怎樣的影響，就去做了一連串相關的實驗去了解到這些參數在這非線性過程中會有怎樣的影響。藉由這一連串的實驗，具有300奈米頻寬的脈衝可以藉由這樣簡單的技術被放大產生出來。倘若這個脈衝經由適當的元件去壓縮，他的脈衝寬度期望可以到達2.4飛秒的等級。

We construct and characterize a femtosecond (fs) 800nm pumped BBO type II collinear optical parametric amplifier (OPA) nonlinear crystal. By tuning the phase matching angle of the BBO crystal, we could obtain the output from 1141 to 1524 nm for the signal beam. The idler tuning range is expected to be 1684 to 2677 nm. The characterizations of this system were that the average output power could be several tens of mW and the pulse duration was estimated to be around 50fs.

Additionally, we employ the multi-beam pump, noncollinear optical parametric amplification and the single-shot geometric scheme to generate the amplified light with ultra-broad bandwidth. To understand the mechanism about this process, we attempt to know what the effect of each variable is. From these results, the pulses with bandwidth over 300 nm are generated by this simple technique and the duration of 2.4 fs is expected after the suitable compressor.