104 research outputs found
Wide bandwidth and high resolution planar filter array based on DBR-metasurface-DBR structures
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
Multiwavelength polarization insensitive lenses based on dielectric metasurfaces with meta-molecules
Metasurfaces are nano-structured devices composed of arrays of subwavelength
scatterers (or meta-atoms) that manipulate the wavefront, polarization, or
intensity of light. Like other diffractive optical devices, metasurfaces suffer
from significant chromatic aberrations that limit their bandwidth. Here, we
present a method for designing multiwavelength metasurfaces using unit cells
with multiple meta-atoms, or meta-molecules. Transmissive lenses with
efficiencies as high as 72% and numerical apertures as high as 0.46
simultaneously operating at 915 nm and 1550 nm are demonstrated. With proper
scaling, these devices can be used in applications where operation at distinct
known wavelengths is required, like various fluorescence microscopy techniques
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