Search

Experimental results are presented on selection of high-order modes in broad aperture laser diode coupled with digital planar hologram (DPH). Computer-generated hologram DPH fabricated on SiO2Gex waveguide core determines the spectrum and field distribution at the laser output. The technology allows a temperature-stable spectral narrowing down to 0.6 nm and a decrease of the far-field distribution width from 6.5° to 2°. These results open a novel route for increasing the brightness and wavelength temperature stabilization of high-power laser diodes by coupling with planar photonic circuit.

Amplification of incoherent light pulses in a relatively short active fiber is treated. Spectral broadening due to the self-phase modulation effect at negligibly small dispersion has been studied theoretically. The expression for the shape of the output spectrum has been obtained for input pulses of arbitrary temporal and spectral shape at various gain coefficients. The expression is found to be simplified in case of a hyperbolic secant temporal shape. The calculated shapes have been compared with the experimentally measured spectra for Q-switched fiber laser nanosecond pulses amplified in Yb-doped fiber, demonstrating excellent agreement of theory and experiment. The spectrum of the output pulse is shown to be composed of two different-scale structures: a narrow central part copying the initial shape and broad exponential tails that grow with increasing output power.

In this paper, the stability of the analytical solutions of the cubic–quintic Ginzburg–Landau equation (CQGLE) in the high-chirp approximation has been studied numerically. The existence domain for the stable solution in the CQGLE parameter set has been found. A temporal and spectral shape of the stable solution as dependent of the cavity parameters has been analyzed. Direct comparison of the spectra with numerical calculations has been performed, demonstrating 10−2–10−4 accuracy of the analytical solution for chirp parameter f>10. The stable solutions represent the dissipative soliton family with only one composite parameter. Inside this family, the pulse shape in the time domain evolves from the conventional soliton shape, sech−2, to a rectangular one in the opposite limit with a parabolic shape as an intermediate one. The obtained theoretical results make it possible to classify experimentally observed highly chirped pulses and to optimize experimental schemes with an all-normal-dispersion cavity.

A Raman gain spectral profile has been measured in a phosphosilicate fiber at high pump and Stokes (signal) wave powers by a coherent anti-Stokes Raman scattering (CARS) technique. It has been shown that the profile saturates homogeneously. The main saturation mechanism is proved to be the pump depletion; i.e., the Raman gain coefficient gR does not depend on the pump and signal wave power of several watts. The possible influence of stimulated Brillouin scattering and four-wave mixing is discussed. In addition, a transient regime of the CARS signal has been experimentally observed and theoretically explained.