Measurement of low-level gain in a visible chemical laser amplifier

Abstract

High precision zero power gain measurements are used to demonstrate that the energy transfer sequence SiO*(b 3 ∏) + Na(3 s 2 S) →SiO(X 1 Σ + ) + Na*(4 d 2 D); Na*(4 d 2 D) → Na(3 p 2 P) + hv(569 nm); Na*(4 d 2 D) + hv(569 nm)→Na(3p 2 P) + 2hv(569 nm) represents a viable visible chemical laser amplifier candidate. Dual beam radiometry is used to advantage in a sensitive and stable measurement system, which provides correction for: 1. source intensity fluctuations, 2. variations in source spectral density, 3. variations in detector spectral response, and 4. gain variations in detector and amplification stages. Experiments are performed to determine the amplification of a probe beam at 569 nm by an extended path length (nominal gain length ∼5 cm) reaction energy transfer zone. For these quantitative gain measurements, the stability of the probe signal sets a limit on the sensitivity of the measurement. Considerable effort was expended to insure equivalent path lengths for probe and reference beams to compensate for source output variations so that the reference signal possesses the same temporal behavior as the probe, and the probe and reference optical systems image the same portion of the source on the detector. A gain coefficient, conservatively estimated as 0.8 to 1.5×10 - 3 cm - 1 , was measured. Based on this result, a Rigrod analysis indicates an expected full laser cavity output power between one and ten watts.