In this study, the bending losses of chalcogenide glass channel optical waveguides consisting of an As2Se3 core and an As2S3 lower cladding layer were numerically evaluated across the astronomical N-band, which is the mid-infrared spectral range between the 8 µm and 12 µm wavelengths. The results reveal the design rules for bent waveguides in mid-infrared astrophotonic devices.

In this study, we conduct guided mode analyses for chalcogenide glass channel waveguides using As2Se3 core and As2S3 lower cladding to determine their single-mode conditions across the astronomical N-band (8-12µm). The results reveal that a single-mode operation over the band can be achieved by choosing a suitable core-thickness.

We examined a Ti-diffused optical waveguide formed on a thin X-cut LiNbO3 substrate for a lower-drive-voltage modulator. Under the single-mode condition, optical mode-size decreases with LiNbO3 substrate thickness below 10 µm. A thin-sheet LiNbO3 modulator could achieve a low-drive-voltage of 1.3 V with a bandwidth of 15 GHz by adopting a narrow electrode-gap.

The add/drop wavelength filter is an essential component in the new-generation photonic network. Microring resonator filters using high index contrast (HIC) optical waveguides are recently attracting attention as add/drop filters owing to their compactness, functionality such as dispersion compensation, and ease of filter synthesis. In particular, the vertically coupled microring resonator (VCMRR) filter is highly suited for the dense, large-scale integration of filter circuits. In this review, the fundamental characteristics advantageous to the add/drop filter nodes are introduced, and the recent progress in the development of vertically coupled microring resonator filters achieved mainly by the author's group is described.

12 on/off power splitters at λ=0.63µm have been produced in LiNbO3 substrates using strain-induced channel waveguides formed by magnetron deposition of surface metal films and lift-off technology. The static strain resulting from thermal expansion mismatch between the substrate and the metal films induces a localized increase in the refractive index via the strain-optic effect. On/off voltage of about 25V has been demonstrated.

The field profile and effective index of a rib waveguide are calculated using an improved semivectorial beam-propagation method using the imaginary-distance procedure. Convergence behavior of the effective index is compared with that obtained by the conventional Crank-Nicholson scheme and with that derived from a Bierwirth-type formula, demonstrating the effectiveness of the present method. Field discontinuities at the interface between different materials are clearly displayed.

Pure bend loss of a fiber with a trench section is calculated by the alternating-direction implicit finite-difference method. The dependence of the loss on the trench location is evaluated. The mechanism of the oscillatory behavior of the loss is discussed in terms of a modal approach in a dielectric slab waveguide.