In-line interferometric femtosecond stimulated Raman scattering spectroscopy

Abstract

We present in-line interferometric femtosecond stimulated Raman scattering (II-FSRS), a new method to measure the spectral Raman intensity and phase over a broad spectral range, potentially in a single shot. An analytic model is developed, that excellently reproduces the measured spectra. Additionally, the performance of II-FSRS is directly compared in experiments to two established techniques, namely femtosecond stimulated Raman scattering and femtosecond Raman induced Kerr-effect spectroscopy.

Femtosecond Stimulated Raman Spectroscopy

“…who use a 200‐kHz Yb‐fiber laser, Gilch and co‐workers who use a 75‐MHz Ti:Sa oscillator and Yb‐fiber amplifier combination, Beier et al . who use an 80‐MHz Ti:Sa oscillator, Dobner et al . who use a homebuilt 1‐MHz Yb‐fiber amplifier, and the ULTRA instrument operating at 10 kHz, respectively.…”

“…Therefore, the most common approach is direct supercontinuum generation in transparent dielectrics based on the Kerr effect. Examples include solids like sapphire,, CaF2 and YAG crystals for Yb‐based laser systems, as well as liquids in flow cells, like water and CCl 4 . Liquids, in principle, allow higher fluences, but solids are much easier to use and produce more stable continua.…”

“…Furthermore, the sensitivity of the detection system is significantly increased compared to regular FSRS, making FRIKES attractive for high‐repetition‐rate laser systems with lower pulse energy . For example, Dobner et al . could increase the signal‐to‐noise ratio from 40:1 for regular FSRS to 615:1 by using FRIKES and accordingly increased integration times to fully exploit the available dynamic range of the detector.…”

“…A technique closely related to FRIKES is the so‐called inline interferometric FSRS (II‐FSRS), which has been pioneered by Fallnich and co‐workers . The main idea is to use two identical probe pulses sharing a common path but separated by polarization.…”

In-line femtosecond common-path interferometer in reflection mode

“…This in-line interferometer is extremely stable and easy to align, leading to a high fringe contrast. Following this pioneering work, other groups have developed similar interferometers [7,18]. Sarpe et al have proposed to use additional birefringent crystals after the sample to reduce the delay between reference and probe pulses down to 200 fs before recording interferences in the spectral domain [7].…”