Sherif F. Hanna

Electronic-resonance-enhanced coherent anti-Stokes Raman spectroscopy of nitric oxide

A dual-pump, electronic-resonance-enhanced coherent anti-Stokes Raman spectroscopy (CARS) technique for the measurement of minor species concentrations has been demonstrated. The frequency difference between a visible Raman pump beam and Stokes beam is tuned to a vibrational Q-branch Raman resonance of nitric oxide (NO) to create a Raman polarization in the medium. The second pump beam is tuned into resonance with rotational transitions in the (1,0) band of the A2Σ+–X2Π electronic transition at 236 nm, and the CARS signal is thus resonant with transitions in the (0,0) band. We observe significant resonant enhancement of the NO CARS signal and have obtained good agreement between calculated and experimental spectra.A dual-pump, electronic-resonance-enhanced coherent anti-Stokes Raman spectroscopy (CARS) technique for the measurement of minor species concentrations has been demonstrated. The frequency difference between a visible Raman pump beam and Stokes beam is tuned to a vibrational Q-branch Raman resonance of nitric oxide (NO) to create a Raman polarization in the medium. The second pump beam is tuned into resonance with rotational transitions in the (1,0) band of the A2Σ+–X2Π electronic transition at 236 nm, and the CARS signal is thus resonant with transitions in the (0,0) band. We observe significant resonant enhancement of the NO CARS signal and have obtained good agreement between calculated and experimental spectra.

Observation of coherent anti-Stokes Raman scattering in the phase-mismatched direction

We have experimentally demonstrated coherent anti-Stokes Raman scattering in both forward and backward directions from thin samples of dipicolinic acid crystalline. The signal observed in the backscattered, phased-mismatched direction is 3 orders of magnitude stronger than would be expected without scattering from the crystals inhomogeneities. We present a theoretical explanation of these results, based on the theory of random diffraction gratings and discuss possible applications.

Observation of coherent anti-Stokes Raman scattering in phase-mismatched direction

We have experimentally demonstrated CARS scattering in the forward and backward directions. The signal observed in the backscattered is of the orders of magnitude stronger than would be expected.