Study of a double resonant network filter for embedded spectroscopy

The aim of this work is to fabricate a high quality factor (20000) spectral filter simultaneously polarization independent and wavelength tunable. Such a device would meet many needs, especially in spectroscopic imaging. For the realization of such a device, resonant gratings are perfectly fitted. Indeed, the position of the resonant peak is naturally tunable by varying the angle of incidence, and quality factors of 10000 are usually attained. However, in general, the spectral response of resonant gratings depends on the polarization, which limits to applications where polarization is known. To solve this problem, we adopt an original approach through an innovative structure consisting of two crossed 1D gratings. Then, we give an example of a polarization independent, reflection filter tunable over 100 nm at a rate of 8.5 nm/° and with a quality factor of 13000. For an application in the near infrared, we propose materials and techniques from the silicon-based microelectronics and we show that it is thus possible to fabricate these structures with the required precision.