We present two laser systems to monitor plasma conditions in a plasma-enhanced chemical vapor deposition chamber. The first optical system is a high-resolution quantum cascade laser-based infrared absorption spectrometer designed to measure the input silane depletion fraction (dissociation efficiency) and to determine the amorphous-to-microcrystalline silicon transition regime. The second optical system is a compact and low-cost laser light scattering device designed to detect the formation of powder particles. In the absence of such particles, the silane depletion fraction provides an in-situ measurement of the film growth rate.