Parametric amplification based on four-wave parametric processes in two-photon resonance

An investigation is made of parametric amplification processes in tow-photon absorption or stimulated Raman scattering (STRS) of pump radiation in gaseous media. It is shown that efficient amplification occurs when the two-photon absorption cross section of the fields being amplified exceeds the two-photon absorption or STRS cross section of the pump radiation and when substantial two-photon absorption of the pump radiation takes place in the thickness of the nonlinear medium. Investigations are made of the noise characteristics of the corresponding parametric amplifiers. It is shown that the main contribution to the noise power is made by four-photon parametric luminescence processes. Calculations are made of the parametric superradiance power in two-photon absorption or STRS of pump radiation in metal vapors. It is shown that such luminescence may be observed in sodium vapor illuminated by a rhodamine laser. An analysis is made of the conditions for triggering an optical parametric oscillator having a broad tuning range in the infrared and ultraviolet, and utilizing the processes studied in vapors and gases. It is established that high-power laser pulses having durations of 10^–5–10^–6 sec are required to pump such an optical parametric oscillator.