Tatsuya Majima

Cavity-resonator-integrated guided-mode resonance filter for aperture miniaturization.

A guided-mode resonance filter integrated in a waveguide cavity resonator constructed by two distributed Bragg reflectors is designed and fabricated for miniaturization of aperture size. Reflection efficiency of >90% and wavelength selectivity of 0.4 nm are predicted in the designed SiO(2)-based filter with 50-μm aperture by a numerical calculation using the finite-difference time-domain method. A maximum reflectance of 67% with 0.5-nm bandwidth is experimentally demonstrated by the fabricated device at around 850-nm wavelength.

Aperture Miniaturization of Guided-Mode Resonance Filter by Cavity Resonator Integration

A small-aperture wavelength filter consisting of a guided-mode resonance grating and a cavity resonator integrated in a SiO2-based waveguide was designed. The operation principle was experimentally confirmed at around 1540-nm wavelength for the first time.

Polarization-independent guided-mode resonance filter with cross-integrated waveguide resonators

A cavity-resonator-integrated guided-mode resonance filter (CRIGF) has been proposed and investigated in order to realize high-efficiency narrowband reflection with a small aperture. The CRIGF consists of a grating coupler integrated in a cavity resonator constructed by a pair of distributed Bragg reflectors on a thin-film waveguide. This time, orthogonally crossed integration of two CRIGFs was demonstrated in order to obtain polarization-independent reflection spectrum. An SiO2-based device with 10 μm aperture was designed and fabricated for around 850 nm wavelength operation, and narrowband polarization-independent reflection was confirmed experimentally.

Guided-mode resonance filter integrated with a resonator of curved DBRs

Narrow-band polarization-dependent high reflection of an optical beam of a small diameter of ~10 μm by a surface dielectric grating structure on a waveguide was demonstrated with guided-mode resonance for the first time.

Small-aperture guided-mode-resonance filter with cavity resonators

A cavity-resonator-integrated guided-mode-resonance filter (CRIGF) consisting of a grating coupler (GC) and a pair of distributed-Bragg-reflectors (DBRs) on a thin film waveguide has been recently proposed and investigated to provide a narrow-band reflection spectrum for an incident wave of a small beam width from the free space. A CRIGF demonstrated so far shows polarization dependence because propagation constants of guided waves excited by GC are different between TE and TM incident waves. In order to construct a polarization-independent guided-mode resonance filter with small aperture, an integration of two CRIGFs crossed each other was proposed and discussed in this paper. A device was designed for a resonance wavelength of 1550 nm and its reflection and transmission spectra were predicted by a newly developed analysis based on the coupled-mode theory. A reflectance of 96 % with 1 nm bandwidth was expected for an incident beam diameter of 10 μm. A test sample working at 846 nm was fabricated and characterized. A Ge:SiO2 guiding core layer was deposited on a SiO2 glass substrate, and GC and DBRs were formed by the electron-beam direct writing lithography. Measured reflection spectra for TE and TM incident beams were well coincident with each other.