2008 SEP 15 - (VerticalNews.com) -- "A real-valued genetic algorithm is used for the realization of higher-order stop-bands in two-dimensional photonic crystals with a square lattice. In this procedure, a number of square rods are arranged in the unit cell of the crystal," scientists in Iran report.

  "Using a genetic algorithm, we determine the dimensions and centers of the rods for a maximum stop-band. In this algorithm, the dimensions and positions of the square rods are represented as real number chromosomes. Some linear decimal crossovers without crossover sites are used. The plane-wave expansion method is used for calculating the photonic band structure corresponding to each chromosome. Four optimized photonic crystal structures are presented," wrote S. Zarei and colleagues ...read more

  2008 SEP 1 - (VerticalNews.com) -- "An optimization technique determining the configuration of optical components in a spatial light modulator is proposed. We study a spatial light modulator composed of a twisted nematic liquid crystal, a polarization state generator, and a polarization state detector," scientists in Seoul, South Korea report.

  "To obtain the desired phase and amplitude modulations, four parameters of the polarization state generator and detector should be optimized. A genetic algorithm is applied in searching the configurations suitable to a given twisted nematic liquid crystal," wrote J. Hahn and colleagues, Seoul National University ...read more

  2008 AUG 18 - (VerticalNews.com) -- According to recent research from Changsha, People's Republic of China, "Numerical analysis of the effects of aberrations on coherently combined fiber laser beams is presented. We prove that traditional beam quality criteria, such as the M-2 factor and the Strehl ratio, do not consider necessary information to evaluate the quality of a coherently combined laser beam."

  "The beam propagation factor (BPF) is introduced and studied as a proper beam quality factor for the coherently combined beam. Two main categories of aberrations, geometry and nongeometry factors, are numerically studied to investigate their effect on beam quality by using the BPF criterion. For a ring-distributed fiber laser array with certain vacancy factor and a RMS value of tilt error, we obtain a semianalytical equation to evaluate their effect on beam quality. We present a brief discussion of those aberrations at the end of this paper," wrote P. Zhou and colleagues ...read more