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On-chip optical filters with designable characteristics based on an interferometer with embedded silicon photonic structures

We demonstrate chip-scale flat-top filters at near-infrared wavelengths using negative index photonic crystal based Mach Zehnder interferometers. Supported by full three-dimensional numerical simulations, we experimentally demonstrate a new approach for engineering high-pass, low-pass, band-pass, and band-reject filters, based on designing the photonic band diagram both within the band-gap frequency region and away from it. We further show that our approach can be used to design filters that have tunable multi-level response for different sections of the spectrum and for different polarizations. This configuration enables deterministic control of the bandwidth and the rejection ratio of filters for integrated photonic circuits.