Compact folded metasurface spectrometer

Abstract

An optical design space that can highly benefit from the recent developments in metasurfaces is the folded optics architecture where light is confined between reflective surfaces, and the wavefront is controlled at the reflective interfaces. In this manuscript, we introduce the concept of folded metasurface optics by demonstrating a compact spectrometer made from a 1-mm-thick glass slab with a volume of 7 cubic millimeters. The spectrometer has a resolution of ~1.2 nm, resolving more than 80 spectral points from 760 to 860 nm. The device is composed of three reflective dielectric metasurfaces, all fabricated in a single lithographic step on one side of a substrate, which simultaneously acts as the propagation space for light. The folded metasystem design can be applied to many optical systems, such as optical signal processors, interferometers, hyperspectral imagers, and computational optical systems, significantly reducing their sizes and increasing their mechanical robustness and potential for integration.

Progresses in the practical metasurface for holography and lens

“…Ultimately, this metaspectrometer is encouraging because it was made very compact compared with the existing spectrometer. Figure 8C is a compact and folded metasurface spectrometer recently introduced by the Faraon group [146]. This spectrometer is also characterized by its extremely compact design like the previous study.…”

“…The metalens has been expected to contribute to the miniaturization of the optical instruments as it can contain much more information than conventional lenses or optic components [99,133,[138][139][140][141][142][143][144][145][146][147][148][149][150]. Figure 8A shows an example of metalens that used the property of the PB phase: The sign of the PB phase is reversed according to the handedness of the incident light [122,144].…”

“…Metalenses can contribute to compact optical systems because they contain characteristics that are not provided by conventional lenses. Figure 8B and C shows the results of the metalens spectrometer using the dispersive nature of the metasurface [133,145,146]. The spectroscopy through the metalens introduced in the Capasso group is implemented through a combination of commercial complementary metal-oxide-semiconductor camera and metalens that has a phase profile in the off-axis focal points [145].…”

Nanostructure-modulated planar high spectral resolution spectro-polarimeter

“…A metasurface is a two-dimensional nanostructure array, which enables control of amplitude, phase, and polarization of the incident light [7]. It has been successfully used in the realizations of polarimeters [8][9][10][11][12], spectral filters and spectrometers [13][14][15][16][17][18], and even spectro-polarimeters [19][20][21][22]. However, there are still several obstacles to overcome and challenges to be addressed.…”

Analog Optical Spatial Differentiators Based on Dielectric Metasurfaces

“…Metamaterials composed of artificial subwavelength structures have exhibited flexible modulation on phase, amplitude, and polarization of electromagnetic waves Metasurfaces, usually regarded as the 2D version of metamaterials, are also of the strong capabilities to manipulate waves and have already generated a great number of promising optical functionalities such as imaging, holography, spectroscopy, and even quantum entanglement . Its monolithic design will afford the special convenience to build optical computational devices.…”