Several optical elements with subwavelength structured (SWS) surfaces have been developed. The SWS has optical features of artificial refractive index, form birefringence, resonance and band-gap effects. This paper describes some applications of form birefringent optical elements and a resonant reflection element. A form-birefringent quarter-wave plate was realized by sputtering the high refractive-index thin film on a SWS substrate. The wavelength dispersion of form birefringence restrains the phase retardance from depending on the wavelength of light. An array of form-birefringent wave-plates is useful for the real-time imaging polarimetry. We developed a real-time polarization imaging system for the visible light. A guided-mode resonant grating with a PLZT wave-guide was designed for optical switches. The PLZT is ferroelectric material with an electro-optic (EO) effect. We made a feasibility study on the optical switching by numerical simulations.
In this presentation we propose the multi-layer subwavelength structures to realize the polarization-sensitive optical elements. The multi-layer structures are fabricated on such consideration that a periodic relief subwavelength structure (we call the base structure later) with depth D1 is first prepared in a substrate with refractive index n1 , then a dielectric material with a refractive index n2 is directionally coated on it with thickness D2 . With the above fabrication process the
coated dielectric material alternatively covers on the ridges or fills in the grooves of base structure to form the multi-layer
structures. The characteristics of the effective indices and the form-birefringence behaved in such structures were investigated. The form-birefringent wave plates and the blazed-binary polarization-selective diffractive optical elements for normal incidence were synthesized with the proposed structures. The optical behaviors included the phase
retardation, diffraction efficiencies, and the polarization contrasts were numerically analyzed with rigorous electromagnetic algorithm. A quarter-wave plate for the operating wavelength of He-Ne laser (λ=632.8 nm) was fabricated and the significant optical performances was obtained.
We have developed several kinds of diffractive optical elements with subwavelength structures for optical information and transmission system. This paper describes the optical elements and fabrication technique, such as antireflection structured surface, a high efficiency computer generated hologram, a non-polarizing resonant grating filter, and a micro retarder array for the real-time polarimeter.