A simplified quasi‐two‐dimensional model for gain optimization in carbon dioxide gasdynamic lasers (GDL)

Abstract

SUMMARYIn this paper a simpliÿed quasi-two-dimensional model for small signal gain optimization in gasdynamic laser is introduced. In order to obtain a homogeneous medium with maximum optical gain in the active medium, by nozzle shape formation, the shock occurrence position is controlled and is postponed to some point behind the laser active medium. Then the method of calculus of variation is used to ÿnd the supersonic part of the nozzle of a gasdynamic laser with maximum gain in the active medium. The interesting result is that the supersonic part of such a nozzle consists of a wedge as the accelerating part of the nozzle, a smooth surface for the uniformization, and ÿnally a channel for the relaxation of the medium. (The middle section is characterized as the geometrical locus of points whose characteristic curves are concurrent at a certain point.) It is also shown that, overlooking a minor di erence in the gain, the nozzle can be chosen to be a shock free one with the ultimate optical uniformity.

Power extraction problem in the externally pumped 16 m gasdynamic lasers: modelling and optimization

“…A change in the density, after the shock wave, results in a change in the refraction index of the medium, and the final spatial distribution of the refraction index will be non-uniform which means we have a low-quality cavity. On the other hand, rises in the pressure and temperature, in a few centimetres, destroy the population inversion and the gain coefficient [40]. Through the relaxation processes, all of the population densities follow the rise in the translational temperature and the state of the gas mixture approaches the state in the combustion chamber.…”

“…For solving the equations, we use the finite-difference method with a non-uniform mesh along the z-axis [45]. The temporal and spatial behaviour of the GDL is simulated by using generalized co-ordinates [45].…”

“…For solving the equations, we use the finite-difference method with a non-uniform mesh along the z-axis [45]. The temporal and spatial behaviour of the GDL is simulated by using generalized co-ordinates [45]. By simulating the system numerically, the gain coefficient, the output intensity, and the temporal and spatial variations of the system variables are determined.…”