Relevance of a midinfrared cavity ring-down diagnostic in the study of a dusty SiH/sub 4/ plasma

We know that cavity ring-down spectroscopy (CRDS) can be of particular relevance in the study of the optical absorption of dust particles in a radio-frequency silane plasma. Although CRDS has historically primarily made use of pulsed lasers as light sources, the experimental design described here is based on 0.1 mW continuous wave multimode lead-salt laser diodes emitting in the midinfrared wavelength range. In order to interrupt the laser beam and reach similar effects to pulsed light sources, we propose a new method called "mode tuning," based on a small detuning of the incoming laser wavelength. This work shows that CRDS has the potential to measure the dynamics of all radicals relevant in the particle nucleation process.