Maxim S. Kuznetsov

Electronic changes of refractive index in intensively pumped Nd:YAG laser crystals

Refractive index changes accompanying changes in population of electron levels of Nd/sup 3+/ ions in a Nd:YAG laser crystal under intensive diode and laser pumping have been studied using a highly sensitive polarization interferometer. An electronic change of the index due to population of the /sup 4/F/sub 3/2/ level is measured to be high (comparable with the thermal component) in the crystal under QCW diode-stack pumping (at 808 nm). The electronic component increased dramatically under pumping by an additional laser (at 266 nm) due to population of a higher-lying level /sup 2/F(2)/sub 5/2/. Analytical estimation reveals a predominating contribution of the well-allowed 4f-5d inter-shell transitions in polarizability of the excited levels /sup 4/F/sub 3/2/ and /sup 2/F(2)/sub 5/2/ both at a testing wavelength of 633 nm and at a wavelength of the strongest laser transition 1064.2 nm.

Trends in stimulated Brillouin scattering and optical phase conjugation

An overview on current trends in stimulated Brillouin scattering and optical phase conjugation is given. This report is based on the results of the “Second International Workshop on stimulated Brillouin scattering and phase conjugation” held in Potsdam/Germany in September 2007. The properties of stimulated Brillouin scattering are presented for the compensation of phase distortions in combination with novel laser technology like ceramics materials but also for e.g., phase stabilization, beam combination, and slow light. Photorefractive nonlinear mirrors and resonant refractive index gratings are addressed as phase conjugating mirrors in addition.

Electronic and thermal refractive index changes in Ytterbium-doped fiber amplifiers

We develop a theoretical framework to analyze the mechanism of refractive index changes (RIC) in double-clad Yb³⁺ doped optical fibers under resonant core or clad pumping, and with signal amplification. The model describes and compares thermal and electronic contributions to the phase shifts induced on the amplified signal at 1064 nm and the probe signal at 1550 nm, i.e. located inside and outside of the fiber amplification band, respectively. The ratio between the thermal and electronic phase shifts is evaluated as a function of the pump pulse duration, the gain saturation, the amplified beam power and for a variety of fiber parameters.

Influence of a backward optical signal on mode instability in Yb 3+ -dopedfiber amplifier

Influence of both backward reflections and laser radiation of independent source propagating in backward direction of ytterbium fiber amplifier on mode instability was investigated. Dependences of mode instability threshold on both power and wavelength of the backward signal were measured. In order to explain threshold behavior we took into account backward signal in our theoretical model.

Mode instability in Yb 3+ -doped fiber amplifiers of continuous and pulsed signal

Spatio-temporal instability of fundamental mode in Yb3+-doped large mode area polarization-maintaining fiber amplifiers was analyzed. Limitations of the amplifier output power and gain were investigated depending on the input signal parameters: spectral width, power level and polarization. The influence of backward reflection of the optical waves on the mode-instability threshold was also examined. The traveling electronic and thermal refractive index gratings following the optically-induced population gratings were found to provide the energy transfer from the main mode to the higher-order modes.

Corrections to "Electronic changes of refractive index in intensively pumped Nd:YAG laser crystals"

In the above-named article [ibid., vol. 39, pp. 910?918, July 2003], Fig. 10 was incorrectly represented. The correct version appears here.