Mechanism for time-dependent oscillations in a CW HF chemical laser unstable resonator

Experimental Study of Time-Dependent Oscillations in a cw HF Chemical Laser Confocal Unstable Resonator

“…The amplitude, frequency, and Fresnel number dependence of the time-dependent oscillations which were predicted to occur on lines whose saturated gain does not fill the confocal unstable resonator were measured experimentally. 3,4 These experiments were performed on the Helios CLI, 15 cm gain length, and CLII, 30 cm gain length, subsonic chemical lasers. The time-dependent oscillations had a period of ~40 ns independent of flow rates.…”

“…7 In response to these experiments, numerical simulations were performed and a mechanism was proposed. 5,6 The time-dependent oscillations of the laser power result from a competition between chemical pumping and radiative deactivation due to lasing. The rate of chemical pumping must be less than the rate of radiative deactivation.…”

“…The oscillations do not occur if the medium is strongly coupled to the optical fields diffractively or geometrically. 5,6 To test this mechanism, calculations were performed to model the CLII laser and vary the coupling of the medium to the optical field both diffractively and geometrically.…”

“…HE objective of this study was to experimentally measure the frequency and amplitude of the time-dependent oscillations that may occur in cw HF chemical lasers that use confocal unstable resonators to extract power. Previous numerical 1,2 and experimental studies 3,4 of these time-dependent oscillations resulted in a proposed mechanism that may be responsible for these oscillations. According to the proposed mechanism, 5,6 the time-…”

“…Previous numerical 1,2 and experimental studies 3,4 of these time-dependent oscillations resulted in a proposed mechanism that may be responsible for these oscillations. According to the proposed mechanism, 5,6 the time-…”