Grating reflector

Patent metadata

Field	Value
Publication number	US-12486160-B2
Application number	US-202217682433-A
Country	US
Kind code	B2
Filing date	Feb 28, 2022
Priority date	Feb 28, 2022
Publication date	Dec 2, 2025
Grant date	Dec 2, 2025

Abstract

A grating reflector. The grating reflector includes a mesh structure defining a mesh plane and having a thickness normal thereto. The mesh structure includes parallel bars and parallel crossbars, which extend along a direction orthogonal to the bars. The bars and crossbars define a 2D grid of elongated holes, each extending through the mesh structure perpendicular to the mesh plane. The holes are elongated along a direction parallel to the bars and have a substantially rectangular shape with rounded corners. The 2D grid is defined by a cross-shaped unit cell having a bar section and an intersecting crossbar section. The grating reflector has a reflectivity in a bandwidth around a center wavelength higher than 0.99. A ratio between the unit cell volume and the center wavelength in the mesh material cubed is between 1.35 and 1.55.

First claim

The invention claimed is:

1 . A grating reflector, comprising:
a mesh structure of a mesh material, the mesh structure defining a mesh plane and having a thickness normal to the mesh plane, the mesh structure comprising a plurality of parallel bars and a plurality of parallel crossbars, the crossbars extending along a direction orthogonal to the bars, the bars and crossbars defining a two-dimensional grid of elongated holes, each hole extending through the mesh structure in a direction normal to the mesh plane, each hole being defined between two adjacent bars and two adjacent crossbars, the holes being elongated along a direction parallel to the bars, the holes having a substantially rectangular shape with rounded corners, the two dimensional grid being defined by a plurality of cross-shaped unit cells, each of the cross-shaped unit cells comprising a bar section and a crossbar section intersecting the bar section to form the cross shape that includes four interior corners, each of the four interior corners being rounded and having a radius of curvature, the bar section having a bar width and a bar section length, the crossbar section having a crossbar width and a crossbar section length; wherein each of the cross-shaped unit cells having a unit cell volume defined by the thickness of the mesh structure, the bar section length, the bar width, the crossbar section length, the crossbar width and by the radii of curvature of the four interior rounded corners; wherein the grating reflector has a reflectivity in a bandwidth around a center wavelength higher than 0.99, and wherein a ratio between the unit cell volume and the center wavelength in the mesh material cubed is between 1.35 and 1.55.

2 . The grating reflector according to claim 1 , wherein the mesh material has a mesh refractive index and wherein the grating reflector comprises a first layer of a first low refractive index material having a first refractive index lower than the mesh refractive index, the first layer extending on a first side of the mesh structure.

3 . The grating reflector according to claim 2 , wherein the first low refractive index material is air.

4 . The grating reflector according to claim 2 , wherein the first layer of the first low refractive index material extends into the holes.

5 . The grating reflector according to claim 2 , comprising a second layer of a second low refractive index material having a second refractive index lower than the mesh refractive index, the second layer extending on a second side of the mesh structure, opposite the first side.

6 . The grating reflector according to claim 5 , wherein the first low refractive index material is air.

7 . The grating reflector according to claim 6 , wherein the first low refractive index material is the same material as the second low refractive index material.

8 . The grating reflector according to claim 1 , wherein the mesh material has a refractive index of at least 3.

9 . The grating reflector according to claim 1 , wherein the mesh material is chosen from GaAs, Silicon, Germanium, In0.49Ga0.51P, InP, AlxGa(1−x) As, AlxGa(1−x)Sb.

10 . The grating reflector according to claim 9 , wherein the mesh material is GaAs.

11 . The grating reflector according to claim 1 , wherein the ratio between the unit cell volume and the center wavelength in the mesh material cubed is between 321913 m −1 *λ c,m +1.27 and 655279 m −1 *λ c,m +1.24, where λ c,m denotes the center wavelength in the mesh material.

12 . The grating reflector according to claim 1 , wherein the bandwidth is at least 10% of the center wavelength.

13 . The grating reflector according to claim 1 , wherein the thickness of the mesh structure, the bar section length, the bar width, the crossbar section length, the crossbar width and the radius of curvature are chosen such that the reflectivity in the bandwidth around the center wavelength is higher than a threshold reflectivity.

14 . The grating reflector according to claim 13 , wherein the threshold reflectivity is at least 0.994.

15 . The grating reflector according to claim 1 , wherein the center wavelength in the mesh material is between 200 nm and 500 nm, such as between 250 nm and 450 nm.

16 . The grating reflector according to claim 1 , wherein the reflectivity is polarization-dependent.

17 . A wavelength tunable or wavelength sweepable vertical cavity surface emitting laser, comprising:
a movable grating reflector comprising a mesh structure of a mesh material, the mesh structure defining a mesh plane and having a thickness normal to the mesh plane and comprising a plurality of parallel bars and a plurality of parallel crossbars, the crossbars extending along a direction orthogonal to the bars, the bars and crossbars defining a two-dimensional grid of elongated holes, each hole extending through the mesh structure in a direction normal to the mesh plane, each hole being defined between two adjacent bars and two adjacent crossbars, the holes being elongated along a direction parallel to the bars, the holes having a substantially rectangular shape with rounded corners, the two dimensional grid being defined by a plurality of cross-shaped unit cells of the grid, each of the unit cells comprising a bar section and a crossbar section intersecting the bar section to form the cross shape that includes four interior corners, each of the four interior corners being rounded and having a radius of curvature, the bar section having a bar width and a bar section length, the crossbar section having a crossbar width and a crossbar section length; wherein each of the unit cells having a unit cell volume defined by the thickness of the mesh structure, the bar section length, the bar section width, the crossbar section length, the crossbar width and by the radii of curvature of the four interior corners; wherein the grating reflector has a reflectivity in a bandwidth around a center wavelength higher than 0.99, and wherein a ratio between the unit cell volume and the center wavelength in the mesh material cubed is between 1.35 and 1.55.

18 . A method for manufacturing a grating reflector, the grating reflector comprising a mesh structure of a mesh material, the mesh structure defining a mesh plane and having a thickness normal to the mesh plane and comprising a plurality of parallel bars and a plurality of parallel crossbars, the crossbars extending along a direction orthogonal to the bars, the bars and crossbars defining a two-dimensional grid of elongated holes, each hole extending through the mesh structure in a direction normal to the mesh plane, each hole being defined between two adjacent bars and two adjacent crossbars, the holes being elongated along a direction parallel to the bars, the holes having a substantially rectangular shape with rounded corners, the two dimensional grid being defined by a plurality of cross-shaped unit cells of the grid, each of the unit cells comprising a bar section and a crossbar section intersecting the bar section to form the cross shape that includes four interior corners, each of the four interior corners being rounded and having a radius of curvature, the bar section having a bar width and a bar section length, the crossbar section having a crossbar width and a crossbar section length, each of the unit cells having a unit cell volume defined by the thickness of the mesh structure, the bar section length, the bar width, the crossbar section length, the crossbar width and by the radii of curvature of the four interior corners;
wherein the method comprises:
selectin

Assignees

• Univ Danmarks Tekniske

Inventors

• Yvind Kresten
• Simonsen Arnhold
• Park Gyeong Cheol
• Ansbaek Thor

Classifications

• H01S5/18363

  comprising air layers · CPC title

• B81B2201/042

  Micromirrors, not used as optical switches · CPC title

• B81B2203/053

  Translation according to an axis perpendicular to the substrate · CPC title

• G02B2005/1804

  Transmission gratings · CPC title

• G02B26/001

  based on interference in an adjustable optical cavity (interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26) · CPC title