We report on the design and performance of a time-resolved Coherent Raman spectroscopy system with time resolution of better than 120 fs. The coherent transients can be traced with more than 75 dB dynamic range while accessing and probing Raman active modes across a 250–2400 cm−1 frequency. The system delivers an equivalent spectral resolution of better than 0.1 cm−1 regarding line bandwidth parameters for probed Raman resonances.
Decays of coherent phonons have been traced with 120 fs resolution in technologically important perovskites of BaSnO
3
and SrTiO
3
. The phonon decay rates of 1.23-1.82 ps
-1
are explained within the framework of anharmonic potential theory.
Time-domain coherent Raman spectroscopy technique with excellent time (<120 fs) and equivalent spectral resolutions (up to ∼0.1 cm −1 ) has been applied to selectively measure ultrafast decay rates of optical phonons in technologically important wide-bandgap materials. The decays of intrinsic vibrations have been traced in time within multiple orders and phonon decay times varied broadly within 0.45−1.7 ps range. Primary decay routes via third-and fourth-order parametric phonon interactions have been analyzed to provide important estimates for zero-temperature decay rates and line widths for the main Raman active vibrations.
We detail a lab-built femtosecond pulse solid-state source of laser-light with continuous tuning from 1030-1350 nm and resultant time-domain CARS measurements on KTP crystal with spectral resolution (<0.1 cm-1) and nearly 80 dB dynamic range.
The decay of multiple Raman active vibrations has been directly traced, in time, in technologically important wide bandgap semiconduction oxides such as BaSnO3 (BSO), STiO3 (STO), and KTiOPO4 (KTP) crystal, which have important applications in laser frequency conversion. A time-domain coherent Raman technique, with excellent time (~120 fs) and spectral resolutions, has been applied to measure the ultrafast decay rates of optical phonons with 350–1500 cm−1 frequencies. Phonon decay mechanisms via phonon energy loss due to second- and third-order parametric processes have been discussed. The correspondingly high equivalent spectral resolution allowed for the determination of the phonon line bandwidths to be within 7.2–8.3 cm−1 (BSO), 8.5–9.7 cm−1 (STO), and 6.2–18.6 cm−1 (KTP).
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