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Considering the random fluctuations of the layer thickness, a method of robust design of broadband EUV multilayers based on multi-objective evolutionary algorithm is presented. Owing to the optimization of multi-objective evolutionary algorithm, the optical performance and robust quality of broadband Mo/Si multilayer can be optimized simultaneously, and then a set of robust designs of aperiodic EUV multilayers, which are insensitive to the thickness errors can be obtained in one single simulation run. The robust designs of broadband Mo/Si multilayers could be used to reduce the production risks of EUV mirrors, and this research demonstrates a great potential of application of multi-objective evolutionary algorithm on the design of optical thin film.

The robust designs of broadband extreme ultraviolet multilayers based on the multiobjective genetic algorithm are validated experimentally. In order to reduce the influence of random layer thickness fluctuations on the great deformation of the experimental reflection of extreme ultraviolet multilayer with a wide angular band, the multiobjective genetic algorithm has been improved to optimize the multilayer system composed by the layer thicknesses which can be controlled precisely. The robust designs of broadband Mo/Si multilayers were fabricated, and the experimental results were presented and analyzed, and then the advantage of robust multilayer designs was demonstrated.The robust designs of broadband extreme ultraviolet multilayers based on the multiobjective genetic algorithm are validated experimentally. In order to reduce the influence of random layer thickness fluctuations on the great deformation of the experimental reflection of extreme ultraviolet multilayer with a wide angular band, the multiobjective genetic algorithm has been improved to optimize the multilayer system composed by the layer thicknesses which can be controlled precisely. The robust designs of broadband Mo/Si multilayers were fabricated, and the experimental results were presented and analyzed, and then the advantage of robust multilayer designs was demonstrated.

A blazed gain grating in a four-level atomic system is theoretically demonstrated. This grating is based on the spatial modulation of Raman gain, which is created by an intensity mask in the signal field. Due to the modulo-2 pi phase modulation, the majority of energy in the amplified probe beam can be deflected into the first-order direction, and a diffraction efficiency higher than 100% is predicted. When an intensity mask having two symmetric domains is adopted, this proposal can give a further possibility of all-optical beam splitting. (C) 2012 Optical Society of America

Double photonic bandgaps (PBGs) can simultaneously appear when double dark resonances in uniform cold atoms are spatially modulated by a resonance standing-wave. Theoretical calculations show that variable and efficient coherent optical control of the PBGs can be achieved by modulating the coupling field and standing-wave. The structures of double PBGs induced by the atomic coherence effect are better than those obtained in the photonic crystal heterostructures. We anticipate that this scheme has potential applications in optical networks for dual-channel all-optical switching or a dual-frequency optical Bragg reflector.