An equiangular spiral photonic crystal fiber has been designed and numerically optimized to obtain its residual chromatic dispersion compensation property in the wavelength range of 1350-1675 nm. The results show that the fiber exhibits an average dispersion of −227 ps/nm-km with a flattened dispersion profile. It is also demonstrated that the fiber shows a high birefringence of 0.0221 at the wavelength 1550 nm. An elliptical air hole is introduced as a defect in the core region and this gives an additional flexibility to tailor the dispersion property. The proposed fiber can be used as an excellent candidate in wavelength-division-multiplexing optical fiber transmission system for residual chromatic dispersion compensation and also for maintaining single polarization.

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A numerical investigation of group birefringence is carried out on a recently reported highly birefringent hollow-core photonic bandgap fiber by use of an efficient vector finite-element method. The hollow fiber core has an area as large as that of approximately four airholes in the cladding region and assumes a rhombic shape with round corners, and the airholes in the cladding region are hexagonal and provide a high air-filling fraction. Numerical results show very high group birefringence of the order of 10(-2) and phase birefringence of the order of 10(-3).

We present here the direct observation of the majority and minority carrier defects generation from wide-band-gap (2.04eV) and thick (2μm) p-AlInGaP diodes and solar cells structures before and after 1MeV electron irradiation by deep level transient spectroscopy (DLTS). One dominant hole-emitting trap H1 (EV+0.37±0.05eV) and two electron-emitting traps, E1 (EC−0.22±0.04eV) and E3 (EC−0.78±0.05eV) have been observed in the temperature range, which we could scan by DLTS. Detailed analysis of the minority carrier injection annealing experiment reveals that the H1 center has shown the same annealing characteristics, which has been previously observed in all phosphide-based materials such as InP, InGaP, and InGaAsP. The annealing property of the radiation-induced defects in p-AlInGaP reveals that multijunction solar cells and other optoelectronic devices such as light-emitting diodes based on this material could be considerably better to Si and GaAs in a radiation environment.

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