Design and fabrication of multichannel photonic crystal wavelength filters to suppress crosstalk of arrayed waveguide grating

Multichannel photonic crystal (PC) wavelength filters have three-dimensional (3D) PCs consisting of Ta₂O₅/SiO ₂ multilayer thin films fabricated by the autocloning method. The PC filters have the unique feature that their transmission wavelengths can be altered by changes not only in refractive indices or thicknesses of the constituent films but also in the in-plane lattice constants. In this study, we focused on connecting an array of PC filters to an arrayed waveguide grating (AWG) to suppress the crosstalk of the AWG. In this application, the transmission wavelength shift that depends on the in-plane lattice constants should be larger than about +40 nm, and the spectrum of the PC filters should be the flat-top type. To satisfy the former requirement, we improved the design of the PC filters and fabricated PC filters having a transmission wavelength shift of +36 nm. For the latter requirement, we applied a two-cavity PC filter and obtained the 3 dB bandwidth of 5.0nm. Finally, we fabricated a module consisting of PC filters and an AWG. The crosstalk of the module was reduced to -20 dB lower than that of the AWG.