A numerical model is developed to simulate stimulated Brillouin scattering (SBS) in high power single-mode fiber amplifiers. The time dependent model incorporates both laser and Stokes wave amplification and initiates the Brillouin scattering from thermal phonons. A frequency chirped laser is used as the seed to suppress SBS. Experiments with Yb-doped fiber amplifiers show good agreement with the modeling. Using experimentally determined parameters, the model is used to predict chirp requirements for multi-kilowatt amplifiers with tens of meters of delivery fiber. A comparison is made between a chirped seed source and random phase modulation for SBS suppression.

Arseny Vasilyev, Amnon Yariv, "Stimulated Brillouin scattering suppression with a chirped laser seed: comparison of dynamical model to experimental data," ABSTRACT When scaling CW single-mode fiber amplifiers to high power, the first nonlinear limitation that appears for narrowlinewidth seed lasers is stimulated Brillouin scattering (SBS). We present a dynamical simulation of Brillouin scattering in a Yb-doped fiber amplifier that numerically solves the differential equations in z and t describing the laser, Stokes and pump waves, the inversion, and the density fluctuations that seed the scattering process. We compare the model to experimental data, and show that a linearly chirped seed laser is an efficient form of SBS suppression; especially for long delivery fibers. The frequency chirp decreases the interaction length by chirping through the Brillouin resonance in a time that is short compared to the fiber transit time. The seed has a highly linear chirp of 10 14 -10 16 Hz/s at 1064 nm which preserves a well-defined phase relationship in time. This method of SBS suppression retains a long effective coherence length for purposes of coherent combining, while at high chirps appears to the SBS as a large linewidth, increasing the threshold. An increase in fiber length increases the laser bandwidth as seen by the SBS, leading to a fiberlength-independent SBS threshold.

The research considers the aspect of the formation of interior lightning in conditions of extensive expenses on heating. In this regard there is important to study features not only of places and model of lightning, but also generation of heat in order to minimize expenses and find alternative technical solutions for building functioning. The relevance is determined by the fact that the problem of low efficiency of thermal energy used to ensure an appropriate microclimate in buildings is typical for many regions. The purpose of this article is to study features not only of places and model of lighting but also generation of heat to minimize expenses and find alternative technical solutions for building functioning. In the work, the methods of calculation methods and mathematical models such as the exergy model of humans were used. The authors have determined that daylight is only one of the complex solutions of the matter of building energy efficiency. Providing the conditions of heating comfort indoors is not less important in the conditions of increasing requirements to energy conservation. The authors consider the compromise between these two requirements without harming human health the main challenge to the energy conservation specialists. The authors have developed the model, which evaluates not only the achievements of technical parameters, but also orientation toward the model of energy consumption of human. The practical application of the developed methodology allows for forecasting not only building heating based on projected technical indicators but also tailored to individual needs.