Shigeo Kittaka

Ultrasmall demultiplexer by use of one-dimensional photonic crystal

Silica-based one-dimensional photonic crystal (1D-PC) is fabricated by use of a high-spatial-frequency grating with input and output surfaces tilted with respect to its periodic direction. An incident beam is coupled with the first photonic band in the second Brillouin zone of the 1D-PC. The output beam angle changes 3 degrees with a wavelength change of 1%. A prototype of an ultrasmall demultiplexer is demonstrated by use of a silica slab waveguide with 1D-PC.

Limits of DWDM with gratings and Fabry-Perots and alternate solutions

High resolution DWDM devices based on the principles of gratings (planar, Bragg, AWG, etc.) and Fabry-Perots (etalon, Lummer-Gehrke plate, etc.) suffer from inherent limitations due to (i) temporal pulse stretching of data, and (ii) broadening of time integrated spectral (demuxed) fringes. While the relation, dνFdt >1, can account for these limitations, our analysis imply that dnF does not represent real, physical frequencies. We explain the broader implications of this interpretation in designing DWDM devices based on gratings and Fabry-Perots and illustrate how to use prisms, photonic crystals and non-linear devices for very high data rate per channel.

Compact and monolithic coarse wavelength-division multiplexer-demultiplexer fabricated by use of a high-spatial-frequency transmission grating buried in a slab waveguide.

A compact and monolithic four-channel demultiplexer with 20-nm spacing was fabricated by use of a high-spatial-frequency transmission grating buried in a silica waveguide. The grating was successfully buried in a silica slab waveguide by overcladding by plasma-enhanced chemical-vapor deposition. The devices size was approximately 5.1 mm x 9.2 mm. The average insertion loss was 13 dB. The average cross talk was -15 dB for adjacent channels and -19 dB for nonadjacent channels. The polarization-dependent loss was estimated to be as low as 0.7 dB.

Superprism Effect of a Triangular One-Dimensional Photonic Crystal Embedded in a Slab Waveguide of a Ta2O5 Core with SiO2 Cladding

We first embedded a triangular one-dimensional photonic crystal in a slab waveguide of a Ta2O5 core with SiO2 cladding. The change in the output angle was 4.8° with the incident wavelength change of 1% for wavelengths of 1400–1500 nm. This value was 1.7 times larger than that of our previous photonic crystal with a SiO2 core. In addition, the maximum diffraction efficiency of 25% was achieved, which was a considerable improvement over the efficiency of our previous one.

Channel Waveguide of One-Dimensional Photonic Crystal

Channel waveguide of one-dimensional photonic crystal was fabricated and evaluated. Because of high order mode propagation on Brillouin zone boundary, light is strongly confined. Bending loss of right angle was 1.2dB.