ABSTRACT
Even though the basic spontaneous parametric process is a purely quantized-field effect, the optical parametric amplification process, or the stimulated parametric process, can be understood within the context of classical electromagnetic theory without invoking any quantum field theory concepts. The repeated-difference-frequency generation process can be used as a model for analyzing the parametric amplification process. Once the phase-matching condition is satisfied, the parametric interaction process will add coherently spatially. The basic tuning characteristics of the parametric process are completely determined by these conditions. As pointed out before, the tunability of the optical parametric process comes from the fact that, when one fixed high-frequency photon breaks down and converts into two lower-frequency photons, the resulting frequencies satisfying the energy-conservation condition are not unique. The bandwidth of the optical parametric process is determined through the energy-conservation and phase-matching conditions primarily by the linewidth of the pump laser, the angular divergence of the pump wave, and the crystal length.
