Chemical laser power spectral performance: a coupled fluid dynamic, kinetic, and physical optics model

Abstract

The simplified chemical fluid dynamic model employed by Sentman in his study of rotational nonequilibrium in cw chemical lasers has been coupled to a 1-D physical optics model of the cavity. Calculations have been performed for both rotational equilibrium and nonequilibrium cases for an unstable resonator with 50% geometric outcoupling. For the rotational equilibrium case, the solution resulted in most of the power being contained in one line (84% in J = 8, 10% in J = 9, and 6% in J = 4). For the rotational nonequilibrium case, 98% of the power is distributed over eleven lines, and the Fabry-Perot and unstable resonator power spectral distributions are almost identical, the major difference being that all lines whose saturated gain region does not extend into the central portion of the unstable resonator are cut off. Comparison of the results for the rotational equilibrium and nonequilibrium kinetic models shows that, for both resonators, the rotational nonequilibrium power is 30% less than the equilibrium case, whereas, for a given kinetic model, the unstable resonator produces only about 6% less power than the Fabry-Perot resonator. For the rotational nonequilibrium case, fluctuations in cw power are shown to occur on lines whose saturated gain zone does not fill the unstable resonator. The amplitude of the fluctuation is determined by the fraction of the resonator filled by the saturated gain zone of the oscillating line, and the frequency of the fluctuation is determined by the location of the intensity peak of the oscillating line.

A simplified model for HF chemical laser amplifier

“…It's a time-consuming task to solve the coupled equations, and there are a number of difficulties to solve this set of equations [9] , such as the stability of solutions associated with the great number of differential equations. Many simplified rate equations, based on different assumptions, are presented for the chemical HF lasers oscillator [10][11][12][13] , and some result are accordance with the experimental results.…”

Modeling of cw Chemical Laser with Annular Unstable Resonator

“…The eigenvalues X of Eq. (B2) is negative and thus the \ a solution is the larger, and let\=M and \ = (B5)where M is the geometric magnification of the resonator.Combining the above results we have l/f 0 t eq =-(M-l)2 /2M (B6)Thus, the distance between edge ray and the annular optical axis Wis(Bll) 2mThis gives the required condition on the magnification of the axicon a M+l m= W~~2~(B12) The virtual source for the feedback ray being launched into the resonator is determined from . Bl Sequence of elements.…”

“…(A2) and (A3) can be combined with Eqs. (2)(3)(4) to provide three ordinary differential equations for d V, dT, and dp. In this manner, the flowfield variation along the streamlines in the mixing zone and the isentropic streamtubes is solved in a coupled fashion.…”

“…2 Both of these studies employed a linear gain volume as opposed to annular laser. These models vary significantly in their ability to model optical performance of cw chemical lasers in a manner that approximates the actual physical mechanism.…”

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

“…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-…”