Phonon dephasing times determined with time-delayed, broadband CARS

TL;DR

This paper introduces a time-delayed broadband CARS method to accurately measure phonon dephasing times across the full spectrum, overcoming spectral distortions caused by non-resonant backgrounds.

Contribution

The study develops a non-resonant background-free TD-BCARS technique for simultaneous phonon dephasing time measurements in various crystalline materials.

Findings

Measured phonon dephasing times in diamond, KTP, and KTA.

Validated the method on amorphous SiO2 for response characterization.

Achieved accurate, full-spectrum phonon lifetime analysis.

Abstract

Coherent Raman scattering techniques as coherent anti-Stokes Raman scattering (CARS), offer significant advantages in terms of pixel dwell times and speed as compared to spontaneous Raman scattering for investigations of crystalline materials. However, the spectral information in CARS is often hampered by the presence of a non-resonant contribution to the scattering process that shifts and distorts the Raman peaks. In this work, we apply a method to obtain non-resonant background-free spectra based on time-delayed, broadband CARS (TD-BCARS) using an intra-pulse excitation scheme. In particular, this method can measure the phononic dephasing times across the full phonon spectrum at once. We test the methodology on amorphous SiO2 (glass), which is used to characterize the setup-specific and material-independent response times, and then apply TD-BCARS to the analysis of single crystals of diamond and ferroelectrics of potassium titanyl phosphate (KTP) and potassium titanyl arsenate (KTA). For diamond, we determine a dephasing time of t = 7.81 ps for the single sp3 peak.