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A structure of a solar concentrating reflector is designed in this paper to improve the usage of solar energy. For the dark image which is the result of the secondary mirror in the new type of the Cassegrain solar concentrating system, a double pyramid system is used to improve this phenomenon. By eliminating the dark image, the system enhanced the concentration ratio and the working efficiency. Meanwhile, both the primary and secondary mirrors are shaped into a square section in order to get a better match with a square photovoltaic receiver. While the length of the primary mirror is 89 m and the block ratio is 20%, the concentration ratio is equal to 118.86. [ABSTRACT FROM AUTHOR]

The optical model of a Cassegrain optical antenna with a confocal double-parabolic reflector structure has been designed, and the propagation characteristics of a hollow laser beam, which could avoid the loss of energy caused by the subreflector center reflection in the optical antenna, has been researched in this paper. By detailed analysis and numerical calculations of a receiving Cassegrain antenna with different deflection angles, the coupling efficiency curve and 3-D distributions of the receiving light intensity for different inclined angles have been obtained. [ABSTRACT FROM AUTHOR]

A new design of a guiding-index photonic crystal fiber which possesses a beam shaping effect and flexible control of dispersion has been proposed in this paper. It can shape a Gaussian beam into a circular hollow beam with certain dimension, which can be used in optical communication systems with a Cassegrain antenna to improve transmission efficiency by avoiding the loss of energy caused by the subreflector center reflection. In addition, its dispersion and confinement loss can be changed in a broad range by slightly adjusting structural parameters under condition that the hollow beam dimension remains about the same. Fairly practical properties, zero dispersion or flattened dispersion, can be obtained when structural parameters are set appropriately. A series of models with different parameters are analyzed and compared. Results of numerical simulation show that the ultra-low dispersion of 1.802 ps/km/nm can be obtained when λ= 1.31 μm. Several modest design parameters are given as well. [ABSTRACT FROM AUTHOR]

The negative refractions are discussed in detail to demonstrate two different two-dimensional photonic crystal structures that undergo negative refractions associated with the backward-wave and forward-wave phenomenon, respectively. The presentation of the left-handed property of effective negative index photonic crystal is followed by a discussion of a backward flowing phase and causality. The forward-wave negative refraction occurs in photonic crystals as a result of anisotropy. This paper is based on the theoretical analysis and is illustrated with the results of finite element method simulations. [ABSTRACT FROM AUTHOR]

In this paper, a one-to-three beam splitter and a T-shaped one-to-two beam splitter are proposed by introducing a V-shaped air gap into a self-collimating photonic crystal (PC). By adjusting the width of the introduced air gap to proper values, the incident beam can be divided into two or three sub-beams. The plane wave expansion method is employed to obtain the equifrequency contours and the band diagram of the PC. The splitting ratios between the sub-beams as a function of the width of the air gap are calculated by using the finite-difference time-domain method. Meanwhile, the field distributions of the light propagation in the structure are presented. [ABSTRACT FROM AUTHOR]