Polarization-selective Gratings Research Articles

光栅反射镜作为激光器后腔镜输出径向偏振光

光栅反射镜作为激光器后腔镜输出径向偏振光

Polarization selectivity of two-layer grating sandwiched between two fused-silica substrates

The polarization selectivity is described based on the two-layer grating sandwiched between two fused-silica substrates. The polarization-selective grating can diffract TE polarization with high efficiency and split TM polarization with good uniformity. With the novel structure, the grating can have high efficiency of sandwiched grating and wideband property of two-layer grating. The modal method is applied to analyze the grating, which corresponds well with the results of rigorous coupled-wave analysis. The physical analysis can give the good guideline to optimize the polarization-selective sandwiched two-layer grating effectively. Such a polarization-selective grating can also have merits of high efficiency for TE polarization and wide angular bandwidth for TM polarization based on the two-layer grating sandwiched between two fused-silica substrate. It is easy to clean and protect the grating surface compared with the surface-relief grating.

A mixed metal dielectric sandwiched grating for polarization-selective reflection

A mixed metal dielectric sandwiched grating is described for polarization-selective reflection. The novel grating is composed of substrate, metal slab, two dielectric grating layers, and covering layer. The polarization-selective grating is optimized by using rigorous coupled-wave analysis for the usual duty cycle of 0.5. With the optimized grating parameters, reflective efficiency of 96.49% can be diffracted into the −1st order for TE polarization. And two-port output of 48.26%/48.27% can be diffracted into the 0th and the −1st orders for TM polarization. Polarization-selective reflection with good performance can be obtained by the mixed metal dielectric sandwiched grating. The usual duty cycle of 0.5 makes it easy and simple to be fabricated for practical applications. Moreover, the polarization-selective beam splitter based on the mixed metal dielectric sandwiched grating has advantages of wide incident wavelength range for TE polarization and angular bandwidth for TM polarization.

Photonic crystals for the visible range fabricated by autocloning technique and their application

We fabricate photonic crystals for the visible range by the ‘autocloning’ technique, in which multilayers are stacked by an appropriate combination of sputter deposition and sputter etching. TiO2/SiO2 and Ta2O5/SiO2 are chosen as materials since they are transparent in the range and give a high contrast of refractive indices. The fabrication technique has flexibility regarding materials and size and is very reliable and reproducible even if the pitch is less than 0.2 μm. We also study the application of photonic crystals to birefringent elements such as waveplates and polarization selective gratings and experimentally verify that they are useful for optical pick-up systems.

Phase gratings with subwavelength structures

Polarization-selective gratings are designed by use of rigorous electromagnetic diffraction theory. The polarizing effects are attained by special surface-relief structures. We present a scheme for coding two different optical functions in one diffractive element. It is based on a combination of the scalar diffraction theory and the effective-medium theory. The diffractive element may be regarded as a combination of a phase element and a subwavelength grating.

Gratings in the resonance domain as polarizing beam splitters

Polarization-selective gratings in the resonance domain of diffractive optics are calculated by use of rigorous electromagnetic diffraction theory. The polarizing effects are attained by special surface-relief structures, and the profile of binary surface-relief gratings is optimized with a nonlinear Newton algorithm to design diffractive polarizing beam splitters.