Spectrometer including metasurface
A spectrometer includes a transparent substrate including a first surface and a second surface that face each other and are substantially parallel to each other; a slit provided on the first surface and through which light is incident onto the transparent substrate; a spectrum optical system including metasurface including a plurality of nanostructures that are two-dimensionally arranged and satisfy a sub-wavelength scattering condition, wherein the metasurface includes a focusing metasurface which includes first nanostructures of the plurality of nanostructures, and is configured to reflect, disperse, and focus the light incident thereon through the slit, at different angles based on respective wavelengths; and a sensor configured to receive the light from the focusing metasurface. When L is a total length of an optical path from the slit to the sensor and D is a thickness of the transparent substrate, L and D satisfy the following inequality: L/D>3.
1. A spectrometer comprising:
a transparent substrate comprising a first surface and a second surface that face each other and are substantially parallel to each other;
a slit provided on the first surface and through which light is incident onto the transparent substrate;
a spectrum optical system comprising at least one metasurface comprising a plurality of nanostructures that are two-dimensionally arranged and satisfy a sub-wavelength scattering condition, wherein the at least one metasurface comprises:
a focusing metasurface which includes first nanostructures of the plurality of nanostructures, and is configured to reflect, disperse, and focus the light incident thereon through the slit, at different angles based on respective wavelengths, the focusing metasurface provided on the first surface or the second surface;
a collimating metasurface provided on the same surface as the focusing metasurface; and
a grating metasurface provided on a surface opposite to the focusing metasurface; and
an aberration control metasurface provided on the surface opposite to the focusing metasurface; and
a sensor configured to receive the light from the focusing metasurface,
wherein an optical path from the slit to the sensor comprises a path from the slit, to the collimating metasurface, to the grating metasurface, to the focusing metasurface, to the aberration control metasurface, and to the sensor, and
wherein, when L is a total length of the optical path and D is a thickness of the transparent substrate, L and D satisfy the following inequality:
L/D> 3.
2. The spectrometer of claim 1 , wherein the collimating metasurface comprises second nanostructures of the plurality of nanostructures, the second nanostructures being two-dimensionally arranged to have a collimating function.
3. The spectrometer of claim 2 , wherein the collimating metasurface is located on the optical path between the slit and the focusing metasurface.
4. The spectrometer of claim 2 , wherein the grating metasurface comprises third nanostructures of the plurality of nanostructures, the third nanostructures being two-dimensionally arranged to have a chromatic dispersion function.
5. The spectrometer of claim 4 , wherein the grating metasurface is located on the optical path between the collimating metasurface and the focusing metasurface.
6. The spectrometer of claim 4 , wherein the grating metasurface and the sensor are provided on the first surface, and
the collimating metasurface and the focusing metasurface are provided on the second surface.
7. The spectrometer of claim 5 , wherein the grating metasurface, the collimating metasurface, the focusing metasurface, and the sensor are two-dimensionally arranged, as seen in a plan view parallel to the first surface and the second surface.
8. The spectrometer of claim 1 ,
wherein the grating metasurface comprises a pattern comprising third nanostructures of the plurality of nanostructures, the third nanostructures being arranged apart from each other in a second direction, and
wherein the pattern is cyclically repeated in a first direction perpendicular to the second direction.
9. The spectrometer of claim 1 , wherein the spectrum optical system further comprises a surrounding structure which surrounds the plurality of nanostructures and comprises at least one among silicon dioxide (SiO2), a glass, and a polymer.
10. The spectrometer of claim 1 , wherein the transparent substrate comprises at least one among silicon dioxide (SiO2), a glass, and a polymer.
11. The spectrometer of claim 1 , wherein the plurality of nanostructures comprise at least one among crystalline silicon (c-Si), amorphous silicon (a-Si), poly silicon (p-Si), gallium phosphide (GaP), gallium arsenide (GaAs), silicon carbide (SiC), titanium dioxide (TiO2), silicon nitride (SiN), and gallium nitride (GaN).
12. The spectrometer of claim 11 , wherein the first nanostructures include a material having a higher refractive index than a material of a surrounding structure.
13. The spectrometer of claim 1 , wherein the focusing metasurface makes the focused light be incident onto different locations of the sensor based on the respective wavelengths, and
wherein the focusing metasurface is disposed at the first surface or the second surface of the transparent substrate and the sensor is disposed at the second surface or the first surface of the transparent substrate, respectively.