Carbery William P, Bizimana Laurie A, Barclay Matthew S, Wright Nicholas D, Davis Paul H, Knowlton William B, Pensack Ryan D, Arpin Paul C, Turner Daniel B
Department of Chemistry, New York University, New York, New York 10003, USA.
Micron School for Materials Science and Engineering, Boise State University, Boise, Idaho 83725, USA.
Rev Sci Instrum. 2024 Mar 1;95(3). doi: 10.1063/5.0187338.
A noncollinear optical parametric amplifier (NOPA) can produce few-cycle femtosecond laser pulses that are ideally suited for time-resolved optical spectroscopy measurements. However, the nonlinear-optical process giving rise to ultrabroadband pulses is susceptible to spatiotemporal dispersion problems. Here, we detail refinements, including chirped-pulse amplification (CPA) and pulse-front matching (PFM), that minimize spatiotemporal dispersion and thereby improve the properties of ultrabroadband pulses produced by a NOPA. The description includes a rationale behind the choices of optical and optomechanical components, as well as assessment protocols. We demonstrate these techniques using a 1 kHz, second-harmonic Ti:sapphire pump configuration, which produces ∼5-fs duration pulses that span from about 500 to 800 nm with a bandwidth of about 200 THz. To demonstrate the utility of the CPA-PFM-NOPA, we measure vibrational quantum beats in the transient-absorption spectrum of methylene blue, a dye molecule that serves as a reference standard.
非共线光学参量放大器（NOPA）能够产生少周期飞秒激光脉冲，非常适合用于时间分辨光谱测量。然而，产生超宽带脉冲的非线性光学过程容易受到时空色散问题的影响。在此，我们详细介绍了包括啁啾脉冲放大（CPA）和脉冲前沿匹配（PFM）在内的改进方法，这些方法可将时空色散降至最低，从而改善NOPA产生的超宽带脉冲的特性。描述内容包括光学和光机械组件选择背后的原理以及评估方案。我们使用1kHz的二次谐波钛宝石泵浦配置展示了这些技术，该配置可产生持续时间约为5飞秒、波长范围约为500至800nm、带宽约为200太赫兹的脉冲。为了证明CPA-PFM-NOPA的实用性，我们测量了亚甲基蓝（一种用作参考标准的染料分子）瞬态吸收光谱中的振动量子拍。
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