Abstract

It can be quite difficult to probe the harsh and potentially nonequilibrium environment of atmospheric pressure Plasma-Assisted Chemical Vapor Deposition (PACVD) reactors [1]. Sensitive measurement of temperature and trace radical concentrations within the reacting substrate boundary layer is a challenging problem in atmospheric pressure reactors due to the highly luminous environment, small spatial scales, and steep thermal and concentration gradients. It is in this environment where the application of sensitive, nonlinear, laser based diagnostic techniques can complement the abilities of more conventional diagnostic techniques such as optical emission spectroscopy (OES) and laser-induced fluorescence (LIF), and allow the detailed measurement of temperature and trace radical concentrations to be made, and compared to models of the deposition environment. The application of a powerful nonlinear laser spectroscopy, degenerate four wave mixing (DFWM), as a gas-phase optical diagnostic has opened the door for significant advancement in the area of atmospheric pressure plasma chemistry, since it can provide high sensitivity and spatial resolution with a coherent, phase conjugate signal which can be readily discriminated against the plasma luminosity [2],

© 1996 Optical Society of America