Dual-wavelengths filter operating at visible wavelength region using subwavelength grating on waveguide structure

A dual-wavelength filter was experimentally demonstrated using subwavelength grating (SWG)/waveguide structure. We designed the structural parameters of the SWG and the waveguide to find the reflection peaks in the visible wavelength region. To investigate the optical response of the designed SWG/waveguide structure, finite-difference time-domain (FDTD) numerical calculations were performed for electromagnetic field distribution. The dual reflection peaks from our proposed structure were predicted in visible wavelength regions by the FDTD calculation. The calculated electromagnetic field distribution also revealed that the reflection peaks were associated with resonances in the SWG and waveguides. We fabricated the SWG/waveguide with typical electron-beam lithography techniques, and two reflection peaks were observed at wavelengths of 486 nm and 590 nm with bandwidths of 45 nm and 58 nm, respectively. These experimental results indicate that dual-wavelength filters can be successfully realized without complex fabrication processes.

This is a post-peer-review, pre-copyedit version of an article published in Optical Review. The final authenticated version is available online at: https://doi.org/10.1007/s10043-019-00541-3.