Nano-glass imprinting technology for next-generation optical devices

Sub-wavelength periodic structures are very attractive for several optical elements with functions such as polarization-independent diffraction, isolation, antireflection, and phase control. In this paper I will review the fabrication of one- and two-dimensional periodic structures upon the surface of oxide glasses using lithograph, etching and glass imprinting. A 4-channel demultiplexer and a superprism demultiplexer were fabricated upon silica plates. The latter exhibited a precise linear relationship between the wavelength and the change of the output angle, which reached 4.8° with the incident wavelength change of 1% for wavelengths of 1400-1500 nm. Fabrication of surface-relief gratings with high spatial frequencies directly on optical glasses was possible using an imprinting process. One-dimensional and two-dimensional periodic structures were formed reproducibly on a phosphate glass surface using thermally durable molds.