KEYWORDS: Resonators, Amplifiers, Signal attenuation, Carbon dioxide, Systems modeling, Gas lasers, Modulation, Mirrors, Laser systems engineering, Astatine
Perturbation exchange processes in two-component active medium such as CO2 : N2 gas mixture were shown to be a
significant factor determined the threshold of self-pulsing oscillations in FFL. Analytical expressions allowed to define
increments and frequencies of the oscillations on the base of stationary lasing parameters were obtained
Numerical simulations of self-pulsing oscillations in fast-flow laser fitted with unstable generator and multipass amplifier were performed. Possibility of the control of the depth of power modulation was shown. A number of governing parameters can be used to vary the regime of lasing in the system. Modulation of output power depending on the pumping rate was observed experimentally in fast-flow CO2 laser.
Numerical simulation indicates that the mechanism of self-pulsing instabilities in fast-flow laser with unstable resonator is connected in many cases with teh rise of relaxation oscillations. Spatial structures, frequencies and increments of the perturbation modes have been calculated in linear approximation. Effects of interaction of relaxation oscillations and flow self-oscillations such as pulling and locking of frequencies were observed. The transformation of relaxation self-oscillations into different saturated regimes of lasing was also investigated. The regimes may be of practical interest due to high pulse repitition rate (up to 104 Hz).
Fast-flow lasers with controllable dynamical regimes were analyzed. Generator-amplifier resonator system considered in the paper was found to possess particular physical mechanism of self-modulated pulsing. The mechanisms lie in the generator and amplifier interaction due to the feedback supplied with the flow. One of the mechanisms is the inversion saturation in the amplifier, which determines the gain of the medium entering the generator. At the same time spatial modulation of the gain profile, as a result of the edge effects in non-stationary optical field, can also affect the regime of lasing. Methods of a regime control based on mechanisms mentioned above are proposed.
New regime of self-pulsing generation in the unstable resonator (UR) of the transverse flow laser was found numerically. The regime is characterized with high pulse repetition rate (Omega) Rapproximately equals 102/(tau) f ((tau) f is the time required for the medium to flow from the edge to the axis of the resonator). It can be considered as relaxation pulsing regime and can be interesting from the point of view of material laser treatment technology. Various regimes of lasing can be easily commuted over.
The dynamics of the lasing of the fast crossflow gas laser with the inhomogeneous steady state pumping in the unstable resonator by means of numerical modeling is investigated. Depending on the system parameters the various dynamical regimes of operation are observed. The detailed investigations of the chaotic lasing features as well as the chaos onset are performed. The possibilities of the control of the laser output characteristics are discussed.
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