Ultrafast mid-infrared spectroscopy by chirped pulse upconversion in 1800-1000cm^−1 region

Jingyi Zhu,John T.M Kennis,Tilo Mathes,Marie Louise Groot,Andreas D Stahl

doi:10.1364/oe.20.010562

Abstract

Broadband femtosecond mid-infrared pulses can be converted into the visible spectral region by chirped pulse upconversion. We report here the upconversion of pump probe transient signals in the frequency region below 1800cm(-1), using the nonlinear optical crystal AgGaGeS4, realizing an important expansion of the application range of this method. Experiments were demonstrated with a slab of GaAs, in which the upconverted signals cover a window of 120cm(-1), with 1.5cm(-1) resolution. In experiments on the BLUF photoreceptor Slr1694, signals below 1 milliOD were well resolved after baseline correction. Possibilities for further optimization of the method are discussed. We conclude that this method is an attractive alternative for the traditional MCT arrays used in most mid-infrared pump probe experiments.

Highlights

The midinfrared spectrum from 1000cm−1 to 3000cm−1 is a region with rich vibrational information relating directly to molecular structures of most organic molecules
Broadband femtosecond mid-infrared pulses can be converted into the visible spectral region by chirped pulse upconversion
We report here the upconversion of pump probe transient signals in the frequency region below 1800cm−1, using the nonlinear optical crystal AgGaGeS4, realizing an important expansion of the application range of this method

Summary

Introduction

The midinfrared (mid-IR) spectrum from 1000cm−1 to 3000cm−1 is a region with rich vibrational information relating directly to molecular structures of most organic molecules. Femtosecond time-resolved UV/Vis pump mid-IR probe spectroscopy is a powerful tool for investigating photo-induced molecular structural and conformational dynamics in fundamental processes in physical chemistry and biology. To realize high time and spectral resolution simultaneously, sensitive multichannel IR array detectors are used which can cover a broad spectral region. Traditional detector array elements for mid-IR are typically based upon liquid nitrogen cooled photocurrent semiconductors of MCT, InSb, or PbSe [11,12]. Ultrafast IR spectroscopy is performed using 1D

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Results

Conclusion