Polarization-insensitive optical filter
The invention consists in a tunable optical filter that has resonant gratings and is adjustable according to the incidence angle. Moreover, the filter has been designed to be insensitive to the polarization of the incident wave. This results in independent behavior between the shape of the filter, spectral width, spectral balance, and maximum transmission.
Principle: Two identical waveguides opposed and superposed, consisting of a stack of layers of different materials having different indices (dielectric and glass). Filtering is performed by excitation of the optical mode of the wavelength to be filtered. Optical parameters include refractive index, thickness of the layers, angle of incidence, grating pitch.
Parameters: are determined based on need, depending on the wavelength of interest. The filtering will then depend only on the angle of incidence, independent of the polarization.
Fabrication: uses traditional industrial methods for microelectronics:
- Optical lithography
- Wet etching
Innovations & Advantages
? High spectral resolution of the order of 15 000. For example: 0.1nm spectral width when centered at 1500 nm.
? Spectrally tunable over a range of 50 nm as a function of the angle of incidence
? Processes derived from the microelectronics industry
Current and Potential Domains of Application