Two-tint pump-probe measurements using a femtosecond laser oscillator and sharp-edged optical filters

We describe a simple approach for rejecting unwanted scattered light in two types of time-resolved pump-probe measurements, time-domain thermoreflectance (TDTR) and time-resolved incoherent anti-Stokes Raman scattering (TRIARS). Sharp edged optical filters are used to create spectrally distinct pump and probe beams from the broad spectral output of a femtosecond Ti:sapphire laser oscillator. For TDTR, the diffusely scattered pump light is then blocked by a third optical filter. For TRIARS, depolarized scattering created by the pump is shifted in frequency by ≈250 cm-1 relative to the polarized scattering created by the probe; therefore, spectral features created by the pump and probe scattering can be easily distinguished.