Innovative optical control: metamaterials, biomimetic photonic devices

Metamaterials are artificial optical materials with subwavelength structures smaller than the incident wavelength as unit elements, and it is known that various optical responses that do not exist in nature such as negative refractive index can be realized. In Kanamori laboratory, studies on fabrication technologies of metamaterials, mechanical reconfigurable metamaterials, application of metamaterials, and so on have been conducted. In addition, we are developing highly efficient nano-optical devices using biomimetics. In order to realize ultra-low-loss nano-photonic devices, we are developing novel smoothing technology for silicon surfaces.

Biomimetics: structural colors and moth eye structures

The color of the peacock's bright feathers is due to structural color generated by nanolattices. The structural color filters enable a variety of colors. Subwavelength periodic structures are formed on Moth-eyes. By mimicking this structures, reflectance of silicon has been reduced by a factor of 100, and the light extraction efficiency of light-emitting diodes has been improved by about 60%. We have also developed inexpensive manufacturing technology using nanoimprint.

Fig. Anti-reflection structures (Moth-eye structures).
Fig. Structural color filters.

Metamaterials: toward innovative optical control

Metamaterial is a structural artificial optical material, and its unique electromagnetic mode depends on the structure. Therefore, metamaterials enable innovative optical function and electromagnetic wave control on demand. We have developed electromagnetically induced transparency metamaterials, novel metamaterials having Fano resonance, metamaterial absorbers, metamaterial sensors with integrated photodiodes, and mechanical reconfigurable metamaterials.

Fig. Electromagnetically induced transparency metamaterials.

Active control: movable nano-photonic devices

Photonic crystals have fine periodic structures in the order of wavelength of light and function to block and confine light. We have developed a wavelength selective filter that controls the optical coupling efficiency of photonic-crystal’s nano-resonator and a variable reflectance filter that controls the light blocking characteristics by controlling the position of photonic crystals with high accuracy using micro-actuators.

Fig. Switching add/drop filter.
Fig. Variable reflectance filter.

Development of novel surface smoothing technologies

Dry-etched silicon surfaces are rough, causing device characteristics to deteriorate and optical loss. We have developed novel surface smoothing technologies that control ultra-precise surface deformation caused by self-diffusion of silicon surface atoms in a high-temperature hydrogen atmosphere. We realize ultra-low-loss nano/micro optical devices and silicon micromechanical parts with excellent mechanical strength.

The equipment developed based on this technology has been commercialized as a minimal laser hydrogen annealing equipment through joint development with Kanamori Laboratory, Sakaguchi E.H VOC Corp., and AIST.
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