We have investigated theoretically and by computer simulation the formation of ultra-short pulses in our laser system using the idea of description of ultra-short coherent optical pulses as temporal Gaussian beams analogous to complex Ermit-Gaussian beams. We have analyzed the laser system with Kerr lens feedback in the phase trajectory of five-dimensional space: the pulse intensity, the width of the pulse, the 'chirp' of the pulse, the phase-front radius of curvature, and the beam size. The investigation of the structure of the phase space transformation shows that the transformation possess an asymptotically stable stationary point and more complicated structure. The analysis of the solutions in our model reveals that chaotic instabilities can be reached through increasing of nonlinear interaction temporal and spatial Gaussian beam.
In this paper we report our investigation of mode-locked and Q-switched regime in Cr<SUP>4+</SUP>:Y<SUB>3</SUB>Al<SUB>5</SUB>O<SUB>12</SUB> laser with synchronous pumping by Nd:YAG laser. We have obtained mode-locked generation of tunable radiation in the range from 1,350 to 1,500 nm. In our investigation we have found position in the stability area where the laser operates on mode-locked or Q-switch regime. In the edge of stability we observe a Q-switch regime of laser operation with rectangular output pulses. We have analyzed the properties of the main optical elements in our laser systems to find out to which extent these elements could be considered as temporal Gaussian systems, and simulated on a computer the ultra-short pulse evolution in the laser resonator for the investigation of the structure of the transformation phase space. The presence of aberration being a source of the ultra-short pulses distortion could drastically complicate a phenomenon.
Tunable, single longitudinal mode output has been obtained from a grazing-incidence grating- tuned Nd:YVO<SUB>4</SUB> slab laser pumped by a quasi-cw diode laser bar. In order to compensate for the very high output coupling losses, a side pumping scheme using a single high angle of incidence reflection at the flat pump face is used to produce very high gain in the laser material. A pulse energy of up to 1 mJ in 200 microsecond(s) has been obtained for a 12 mJ pump pulse. The almost TEM<SUB>00</SUB> output remained single longitudinal mode for periods of several minutes without active stabilization and could be tuned over a wavelength range of greater than 1 nm.