Wide bandwidth and high resolution planar filter array based on DBR-metasurface-DBR structures

TL;DR

This paper presents a novel planar filter array using DBR-metasurface-DBR structures that offers wide bandwidth, high resolution, and independent wavelength control, suitable for on-chip spectrometers.

Contribution

It introduces a new design of optical filter array with independently tunable center wavelengths using metasurfaces within a DBR-based Fabry-Pérot resonator.

Findings

Array covers 250 nm wavelength range around 1550 nm

Quality factors exceed 700

Filters can be integrated with photodetectors for on-chip spectrometry

Abstract

We propose and experimentally demonstrate a planar array of optical bandpass filters composed of low loss dielectric metasurface layers sandwiched between two distributed Bragg reflectors (DBRs). The two DBRs form a Fabry-P\'erot resonator whose center wavelength is controlled by the design of the transmissive metasurface layer which functions as a phase shifting element. We demonstrate an array of bandpass filters with spatially varying center wavelengths covering a wide range of operation wavelengths of 250 nm around {\lambda} = 1550 nm ({\Delta}{\lambda}/{\lambda} = 16%). The center wavelengths of each filter are independently controlled only by changing the in-plane geometry of the sandwiched metasurfaces, and the experimentally measured quality factors are larger than 700. The demonstrated filter array can be directly integrated on top of photodetector arrays to realize on-chip high-resolution spectrometers with free-space coupling.