Yoshiaki Kanamori

We fabricated a two-dimensional subwavelength structured (SWS) surface upon a crystal silicon substrate. The SWS surface was patterned by electron beam lithography and etched by an SF(6) fast atom beam. The SWS grating had a conical profile, the period was 150 nm, and the groove was approximately 350 nm deep. The reflectivity was examined at 2002500-nm wavelengths. At 400 nm the reflectivity decreased to 0.5% from the 54.7% of the silicon substrate. We also used HeNe laser light to examine the r

An ordered anodic porous alumina membrane has been used as a lithographic mask of SF6 fast atom beam etching to generate a 100 nm period antireflection structure on a silicon substrate. The antireflection structure consists of a deep hexagonal grating with 100 nm period and aspect ratio of 12, which is a fine two-dimensional antireflection structure. In the wavelength region from 400 to 800 nm, the reflectivity of the silicon surface decreases from around 40% to less than 1.6%. The measured resu

We investigate theoretically and experimentally transmission color filters using silicon subwavelength gratings on quartz substrates. Each grating area is 120 mum-square, which is suitable pixel size for displays and multichannel detectors. In the fabrication, electron beam lithography and fast atom beam etching are used. The grating periods are 400, 350, and 440 nm for the red, green, and blue filters, respectively. The transmission spectrum obtained from a coupling between an incident light an

A two-dimensional subwavelength grating (SWG) has been fabricated on a GaAlAs light-emitting diode (LED). The SWG is patterned by electron beam lithography and etched by fast atom beam with Cl/sub 2/ and SF/sub 6/ gases. The fabricated grating has 200 nm period and the tapered grating shape with aspect ratio of 1.38 to prevent reflection in the spectral region including 850 nm light emission. The emission is increased by 21.6% at the normal emission angle. The total emittance is increased by 60%

A wavelength-selective variable-reflection filter is proposed, in which a guided resonance in a photonic crystal (PC) slab is controlled by microelectronic mechanical actuators. A narrow wavelength response is generated by the guided resonance of PC slab, and the variable optical response at the wavelength is caused by evanescent-wave coupling to a substrate. The coupling is controlled by microelectromechanical actuators. The proposed filter has been fabricated by silicon micromachining and the

We fabricated a two-dimensional subwavelength-structured (SWS) surface on a glass substrate. The SWS surface was patterned by electron-beam lithography and etched by an SF 6 fast atom beam. The SWS surface consisted of tapered gratings with a 150 nm period and a 150 nm deep groove. The reflectivity at wavelengths from 400 nm to 2000 nm was measured and compared with the results calculated on the basis of rigorous coupled-wave analysis. At wavelengths from 400 nm to 800 nm, the reflectivity of th

Antireflection (AR) layers at the tips of optical fibers are indispensable in high efficiency and low noise applications. We realized the AR structures with two-dimensional binary subwavelength gratings (SWGs) at the tips of optical fibers by using a dedicated UV nanoimprint machine. Using this technique, ideal AR structures with desired refractive indices can be realized at low cost in principle. The SWG with the period of 700 nm was fabricated at the tip of a single-mode optical fiber for opti

We fabricated a two-dimensional subwavelength grating (SWG) on a GaSb substrate. The SWG was patterned by electron-beam lithography and etched by a fast atom beam with SF6 and Cl2 gases. The SWG consisted of tapered gratings with a 350-nm-period and a 1280-nm-deep groove. The reflectivity at wavelengths from 500 nm to 2300 nm was measured and compared with the results calculated on the basis of rigorous coupled-wave analysis (RCWA). At wavelengths from 500 nm to 2000 nm, the SWG decreased the re

Metamaterials have attracted a great deal of attention as artificial electromagnetic materials having unique optical characteristics, and various innovative optical applications have been expected. Micro electromechanical systems (MEMS)-based reconfigurable metamaterials are candidate technologies for active optical control. In this paper, we focus on MEMS-based reconfigurable metamaterials operated in the optical region between visible and near-infrared wavelengths. A brief overview of static o

We investigate structural color filters theoretically and experimentally using polymer-based guided-mode resonant gratings fabricated by nanoimprint lithography. Each grating area is 200×200 µm2, which is a suitable pixel size for displays and multichannel detectors. In the mold fabrication, electron beam lithography and fast atom beam etching are used. The grating periods are 600, 350, and 300 nm for the red, green, and blue filters, respectively. Reflectivity is measured as a function of wavel

We propose pitch-variable guided resonance filters for continuous resonant-wavelength tuning at telecom frequencies. Since the optical response is affected by not only the grating period but also the filling factor, in consideration of these parameters, the filter is designed to be tuned smoothly to a selective wavelength by using comb-drive actuators. The grating with the initial period of 860 nm is fabricated with high accuracy. When the grating is expanded, the resonant wavelength shifts to l

We propose a guided-mode resonant grating (GMRG) filter using silicon-on-insulator wafer. In the fabrication, electron beam lithography and fast atom beam etching are used. The periods of the three filters are 680, 700, and 720 nm, respectively. The reflectivity is measured to be nearly 100% at the wavelength of 1502 nm for the 700 nm period GMRG filter with a fill factor of 0.760. The optical properties of the filters are analyzed using a rigorous coupled-wave analysis (RCWA).

We fabricated reflection color filters of the three primary colors with wide viewing angles using silicon two-dimensional subwavelength gratings on the same quartz substrate. The grating periods were 400, 340, and 300 nm for red, green, and blue filters, respectively. All of the color filters had the same grating thickness of 100 nm, which enabled simple fabrication of a color filter array. Reflected colors from the red, green, and blue filters under s-polarized white-light irradiation appeared