# US 10,312,277 B2 · Variable optical filter and a wavelength-selective sensor based thereon

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- Number: US 10,312,277 B2
- Document ID: US10312277B2
- Status: Granted
- Kind: B2
- Application number: 15/837,180
- Filed: 2017-12-11
- Published: 2018-04-19
- Granted: 2019-06-04
- Earliest claimed: 2013-01-29
- Assignees: Viavi Solutions Inc.
- Applicants: Viavi Solutions Inc.
- Inventors: Karen Denise Hendrix; Charles A. Hulse; Richard A. Bradley; Jeffrey James Kuna
- Web page: https://patentgrep.com/patent/US10312277B2

## CPC

- H10F 39/8053: {Colour filters}
- G01J 3/0259: {Monolithic}
- G01J 3/26: using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters
- G02B 5/281: {designed for the infrared light}
- G02B 5/288: {comprising at least one thin film resonant cavity, e.g. in bandpass filters}
- H10F 39/024: {of coatings or optical elements}
- H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
- H10F 39/8057: {Optical shielding}
- H10F 39/807: {Pixel isolation structures}
- H10F 39/809: {of hybrid image sensors}
- G01J 2003/1226: {Interference filters}
- G01J 2003/1234: {Continuously variable IF [CVIF]; Wedge type}
- G01J 2003/1239: {and separate detectors}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A variable optical filter is disclosed including a bandpass filter and a blocking filter. The bandpass filter includes a stack of alternating first and second layers, and the blocking filter includes a stack of alternating third and fourth layers. The first, second and fourth materials each comprise different materials, so that a refractive index of the first material is smaller than a refractive index of the second material, which is smaller than a refractive index of the fourth material; while an absorption coefficient of the second material is smaller than an absorption coefficient of the fourth material. The materials can be selected to ensure high index contrast in the blocking filter and low optical losses in the bandpass filter. The first to fourth layers can be deposited directly on a photodetector array.

## Claims

### Claim 1

An optical filter comprising:
a first filter,
the first filter comprising:
a first plurality of layers including a first material having a first refractive index, and
a second plurality of layers alternating with the first plurality of layers,
the second plurality of layers including a second material having a second refractive index,
the first refractive index being smaller than the second refractive index; and
a second filter including the first material.

### Claim 2 (depends on 1)

The optical filter of claim 1, wherein at least one of the first filter or the second filter is deposited directly on a photodetector array.

### Claim 3 (depends on 1)

The optical filter of claim 1, wherein the first filter is disposed over a substrate.

### Claim 4 (depends on 1)

The optical filter of claim 1, wherein at least one layer of the first plurality of layers is between at least one layer of the second plurality of layers and a substrate.

### Claim 5 (depends on 1)

The optical filter of claim 1, wherein at least one layer of the second plurality of layers is an external most layer.

### Claim 6 (depends on 1)

The optical filter of claim 1, wherein the first filter has a laterally variable thickness.

### Claim 7 (depends on 1)

The optical filter of claim 1, wherein the first refractive index is between 1.35 and 1.6.

### Claim 8 (depends on 1)

The optical filter of claim 1, wherein the first material includes silicon dioxide.

### Claim 9 (depends on 1)

The optical filter of claim 1, wherein the first material and the second material include dielectric materials.

### Claim 10 (depends on 1)

The optical filter of claim 1, wherein the second filter has a laterally variable thickness.

### Claim 11

An optical filter comprising:
a bandpass filter including a first material; and
a blocking filter,
the blocking filter comprising:
a plurality of higher refractive index material layers having a refractive index between 2.6 and 4.5, and
a plurality of lower refractive index material layers alternating with the plurality of higher refractive index material layers,
the plurality of lower refractive index material layers including the first material.

### Claim 12 (depends on 11)

The optical filter of claim 11, wherein the blocking filter has a laterally variable thickness.

### Claim 13 (depends on 11)

The optical filter of claim 11, wherein the plurality of lower refractive index material layers include silicon dioxide.

### Claim 14 (depends on 11)

The optical filter of claim 11,
wherein the plurality of higher refractive index material layers include a second material, and
wherein the second material has an absorption coefficient larger than an absorption coefficient of the first material.

### Claim 15 (depends on 11)

The optical filter of claim 11, wherein the bandpass filter includes a material having a refractive index between 1.35 and 1.6.

### Claim 16 (depends on 11)

The optical filter of claim 11, wherein the blocking filter is deposited directly on a photodetector array.

### Claim 17 (depends on 11)

The optical filter of claim 11, wherein the blocking filter is disposed over a substrate.

### Claim 18 (depends on 11)

The optical filter of claim 11, wherein at least one layer of the plurality of higher refractive index material layers is between at least one layer of the plurality of lower refractive index material layers and a substrate.

### Claim 19 (depends on 11)

The optical filter of claim 11, wherein at least one layer of the plurality of higher refractive index material layers is an external most layer.

### Claim 20 (depends on 11)

The optical filter of claim 11, wherein the bandpass filter includes a material having a refractive index between 1.8 and 2.5.