Vibrational circular dichroism signal enhancement using self-heterodyning with elliptically polarized laser pulses.

Vibrational circular dichroism (VCD) spectra were recorded using elliptically polarized ultrashort laser pulses, produced with the help of a photoelastic modulator. The short polarization axis of the elliptical light acts as a phase-locked local oscillator field, heterodyning the chiral signal generated by the field along the long polarization axis. This leads to VCD signals that increase linearly with the ellipticity of the probe pulses and enhanced signal to noise, which is expected to improve recently reported transient VCD scans. An analogous scheme allows for vibrational optical rotary dispersion measurements. The techniques are compared with similar approaches using both a linear response picture and the Jones matrix calculus.