# US 11,442,002 B2 · Cuvette having high optical transmissivity and method of forming

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- Number: US 11,442,002 B2
- Document ID: US11442002B2
- Status: Granted
- Kind: B2
- Application number: 16/901,352
- Filed: 2020-06-15
- Published: 2020-10-01
- Granted: 2022-09-13
- Earliest claimed: 2017-12-06
- Assignees: California Institute of Technology
- Applicants: California Institute of Technology
- Inventors: Axel Scherer; Amirhossein Nateghi; Taeyoon Jeon; Frank T. Hartley
- Web page: https://patentgrep.com/patent/US11442002B2

## CPC

- G01N 21/0303: {Optical path conditioning in cuvettes, e.g. windows; adapted optical elements or systems; path modifying or adjustment (G01N21/031 - G01N21/15 take precedence)}
- G01N 1/42: Low-temperature sample treatment, e.g. cryofixation
- G01N 1/44: Sample treatment involving radiation, e.g. heat
- G01N 21/171: {with calorimetric detection, e.g. with thermal lens detection}
- G01N 21/255: {Details, e.g. use of specially adapted sources, lighting or optical systems}
- G01N 21/35: using infrared light (G01N21/39 takes precedence)
- G01N 21/6452: {Individual samples arranged in a regular 2D-array, e.g. multiwell plates}
- G01N 21/3504: for analysing gases, e.g. multi-gas analysis
- G01N 21/3577: for analysing liquids, e.g. polluted water
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

The present disclosure is directed toward optical elements, such as sample cuvettes, lenses, prisms, and the like, whose transmissivity is increased by the addition of a geometric anti-reflection layer disposed on at least one surface of the optical element, where the geometric anti-reflection layer includes a plurality of geometric features that collectively reduce the reflectivity of the interface between the surface and another medium. As a result, more of an optical signal incident on the surface passes through the interface. In some embodiments, every surface through which an optical signal passes includes a geometric anti-reflection layer. Due to the increased transmissivity of the optical element, in some embodiments, the use of low-cost, high-refractive-index materials, such as conventional silicon, is enabled.

## Claims

### Claim 1

An optical element comprising a cuvette that includes:
a body that includes first and second surfaces, each of the first and second surfaces comprising a first material; and
a first plurality of features that have substantially the same height, the first plurality of features collectively defining a first geometric anti-reflection (GAR) layer, each feature of the first plurality thereof projecting outward from the first surface from a first base located at the first surface to a first tip, wherein each feature of the plurality thereof has a first cross-section that increases monotonically from the first tip to the first base;
a second plurality of features that have substantially the same height, the second plurality of features collectively defining a second GAR layer, each feature of the second plurality thereof projecting outward from the second surface from a second base located at the second surface to a second tip, wherein each feature of the second plurality thereof has a second cross-section that increases monotonically from the second tip to the second base;
wherein a flat surface comprising the first material is characterized by a first reflectivity for a first light signal;
wherein the first GAR layer and the first surface are collectively characterized by a second reflectivity for the first light signal that is lower than the first reflectivity; and
wherein the second GAR layer and the second surface are collectively characterized by a third reflectivity for the first light signal that is lower than the first reflectivity.

### Claim 2 (depends on 1)

The optical element of claim 1 wherein the plurality of first tips collectively defines a first boundary, and wherein the refractive index of the first GAR layer increases adiabatically from the first boundary to the first surface.

### Claim 3 (depends on 1)

The optical element of claim 1 wherein the first cross-section increases non-linearly from the first tip to the first base.

### Claim 4 (depends on 1)

The optical element of claim 1 wherein the first material is silicon.

### Claim 5 (depends on 1)

The optical element of claim 1 wherein each feature of the first plurality thereof comprises the first material.

### Claim 6 (depends on 1)

The optical element of claim 1 wherein each feature of the first plurality thereof has a sidewall that extends between the first base and the first tip, and wherein at least one sidewall of the first plurality thereof includes a surface feature.

### Claim 7 (depends on 1)

The optical element of claim 1 wherein the first surface is non-planar.

### Claim 8 (depends on 1)

The optical element of claim 1 wherein the first light signal is characterized by a spectral range that extends from a first wavelength to a second wavelength, the first wavelength being shorter than the second wavelength, and wherein the features of the first plurality thereof are separated by an average spacing that is less than the first wavelength.

### Claim 9 (depends on 8)

The optical element of claim 8 wherein the first wavelength is 2 microns and the second wavelength is 15 microns.

### Claim 10

An optical element that includes a cuvette for holding a test sample, the cuvette comprising:
a body that includes first, second, third, and fourth surfaces, each comprising a first material that is characterized by a first refractive index for a first light signal;
a first geometric anti-reflection (GAR) layer disposed on the first surface, the GAR layer including a first plurality of features that have substantially the same height and extend normally from the first surface, wherein each feature of the first plurality thereof extends between a first base located at the first surface and a first tip located at a first boundary, and wherein each feature of the first plurality thereof has a first cross-section that increases monotonically from the first tip to the first base, and further wherein the first boundary is characterized by a first effective refractive index that is lower than the first refractive index; and
a second GAR layer comprising a second plurality of features that extend normally from the second surface, wherein each feature of the second plurality thereof extends between a second base at the second surface and a second tip, and wherein the plurality of second tips collectively defines a second boundary that is characterized by a second effective refractive index that is lower than the first refractive index.

### Claim 11 (depends on 10)

The optical element of claim 10 wherein the optical element comprises a lens or a prism.

### Claim 12 (depends on 10)

The optical element of claim 10 wherein each feature of the first plurality thereof comprises the first material.

### Claim 13 (depends on 10)

The optical element of claim 10 wherein the first material is silicon and the first light signal has a spectral width that includes at least a portion of the mid-infrared spectral range.

### Claim 14 (depends on 10)

The optical element of claim 10 wherein each feature of the first plurality thereof has a sidewall that extends between the first base and the first tip, and wherein at least one sidewall of the first plurality thereof includes a surface feature.

### Claim 15 (depends on 10)

The optical element of claim 10 wherein the first surface is non-planar.

### Claim 16

A method for forming a cuvette for holding a test sample, the method comprising:
providing a body having first, second, third, and fourth surfaces that comprise a first material having a first refractive index for a first light signal;
forming a first geometric anti-reflection (GAR) layer on the first surface, wherein the first GAR layer includes a first plurality of features that have substantially the same height and extend normally from the first surface from a first base located at the first surface to a first tip at a first boundary, and wherein each feature of the first plurality thereof has a first cross-section that increases monotonically from the first tip to the first base, and further wherein the first boundary is characterized by a first effective refractive index that is lower than the first refractive index; and
forming a second GAR layer on the second surface, wherein the second GAR layer includes a second plurality of features that have substantially the same height and extend normally from the second surface from a second base located at the second surface to a second tip at a second boundary, and wherein each feature of the second plurality thereof has a second cross-section that increases monotonically from the second tip to the second base, and further wherein the second boundary is characterized by a second effective refractive index that is lower than the first refractive index.

### Claim 17 (depends on 16)

The method of claim 16 wherein the optical element is formed such that it includes at least one of a lens and a prism.

### Claim 18 (depends on 16)

The method of claim 16 wherein each of the first surface and the first plurality of features is formed by etching a first layer.

### Claim 19 (depends on 16)

The method of claim 16 wherein the first plurality of features is formed by depositing a second material on the first surface.

### Claim 20 (depends on 19)

The method of claim 19 wherein the second material and the first material are substantially the same material.

### Claim 21 (depends on 16)

The method of claim 16 wherein the first GAR layer is formed such that the first cross-section increases linearly from the first tip to the first base.

### Claim 22 (depends on 16)

The method of claim 16 wherein the first light signal is characterized by a spectral range that extends from a first wavelength to a second wavelength, the first wavelength being shorter than the second wavelength, and wherein the features of the first plurality thereof are separated by an average spacing that is less than the first wavelength.

### Claim 23 (depends on 22)

The method of claim 22 wherein the first wavelength is 2 microns and the second wavelength is 15 microns.

### Claim 24 (depends on 16)

The method of claim 16 wherein each feature of the first plurality thereof is formed such that it has a sidewall that extends between the first base and the first tip, and wherein at least one sidewall of the first plurality thereof includes a surface feature.