Theory of energy gain in a laser-amplifier based on a photon-branched chain reaction: Auto-wave amplification mode under the condition of input signal focusing

Abstract

Huge energy gain is detected theoretically in a pulsed chemical laser amplifier based on a photon-branched chain reaction initiating in a gaseous disperse medium composed of H2-F2-O2-He and Al particles by focused external infrared radiation. It is shown that this effect is observed due to the possibility of the ignition of the laser–chemical reaction into an initial small focal volume of an active medium. It then spreads out of this minimal volume spontaneously in the auto-wave regime without external power sources and subsequently fills the whole volume of the laser cavity with a high intensive electromagnetic field as self-supporting cylindrical photon-branching zones formed by the paths of the rays inside the unstable telescopic cavity. Calculations show that the ignition of an auto-wave photon-branched chain reaction under the condition of external signal focusing strongly reduces the input pulse energy necessary for initiation up to ∼10−8 J, and thereby allows a huge value of the energy gain of ∼1011. The observed effect of this huge laser energy gain makes it possible to construct a self-contained laser with kilojoule output energy, which can be initiated by a very weak source signal.

Giant energy gain in a pulsed HF laser based on a photon-branched chain reaction

“…duration of the input signal, τ in ,was selected so that the enclosed energy in the focal volume, V f ~ 10 -7 cm 3 , was enough for the evaporation of particles of aluminum, for the initiation of the PBCR and, in the end, for deriving the generation of the laser. Calculations 6,7 show that at a given intensity in the field at the focal point, the threshold value τ in for a master oscillator generating radiation is 250 ns for the selected composition of the active laser mixture containing dispersed Al particles.…”

“…[2][3][4][5][6][7][8] We have considered the case of a confocal telescopic cavity with spherical mirrors (Fig. 1).…”

“…The factors of screens passage P 1,2 (r) are approximated by exponential functions. [2][3][4][5][6][7][8] The optimal laser variant was found 2-8 to have a four-pass unstable telescopic cavity of length L = 49.5 cm, when the diameter of the first mirror is d 1 = 14 cm and that of the second mirror d 2 = 5.98 cm, and the focal length of the second mirror is F = 53 cm. In our calculation we assumed that the cavity is filled with a high-energy-capacity working mixture, with composition H 2 :F 2 :O 2 :He = 166:334:40:210 torr, containing fine passivated aluminum particles of radius r 0 = 0.2 µm and concentration N 0 = 1.3×10 8 cm 3 .…”

Laser-Induced Photon-Branched Chain Reaction in a Chemically-Active Gas-Dispersed Medium

“…Theoretical investigations [1][2][3][4][5][6][7][8][9] have been carried out for the problem of photon branching in a two-phase (consisting of a gas and disperse particles) chemically active media. It has been shown that the introduction of a certain concentration of ultradisperse particles into the active medium of a chemical laser based on a chain reaction, and further their (particles) evaporation by external infrared (IR) radiation, can result in the generation of coherent radiation of energy considerably higher than the energy of an initiating input pulse at same frequency.…”

“…We have developed a relatively simple HF laser kinetic model [1,2] which includes the most important physical-chemical kinetics features under the assumption of rotational-translational nonequilibrium, 2 Laser Chemistry making it possible to calculate the specific energy of the coherent radiation, the pulse duration, the effective chain length of the reaction between fluorine and hydrogen, and the chemical and engineering efficiencies of the laser. This model was supplemented with an electrodynamical model [2][3][4][5][6][7][8][9] of the pulsed laser based on a solution of the wave equation. The wave approach for the description of a pulsed chemical HF laser amplifier based on a PBCR in an unstable telescopic cavity enables the detection of interesting optical effects in an active two-phase medium of H 2 -F 2 -O 2 -He and Al particles and also of the new properties of the laser.…”