  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.
