# US 11,079,547 B2 · Broadband star coupler

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- Number: US 11,079,547 B2
- Document ID: US11079547B2
- Status: Granted
- Kind: B2
- Application number: 16/104,083
- Filed: 2018-08-16
- Published: 2019-02-21
- Granted: 2021-08-03
- Earliest claimed: 2017-08-17
- Assignees: Rockley Photonics Limited
- Applicants: Rockley Photonics Limited
- Inventors: Andrea Trita; Thomas Pierre Schrans
- Web page: https://patentgrep.com/patent/US11079547B2

## CPC

- G02B 6/2804: {forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers}
- G02B 5/1861: {Reflection gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials (G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence)}
- G02B 6/12016: {characterised by the input or output waveguides, e.g. tapered waveguide ends, coupled together pairs of output waveguides}
- G02B 6/124: Geodesic lenses or integrated gratings
- G02B 6/2808: {using a mixing element which evenly distributes an input signal over a number of outputs}
- G02B 6/29308: {Diffractive element having focusing properties, e.g. curved gratings (Rowland circle spectrometers G01J3/20)}
- G02B 6/29301: {based on a phased array of light guides (integrated arrayed waveguide gratings G02B6/12009)}
- G02B 6/2931: {Diffractive element operating in reflection}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An optical device. In some embodiments, the optical device includes a first interface; a second interface; a first plurality of waveguides, at the first interface; a second plurality of waveguides, at the second interface; and a free propagation region. A first waveguide of the first plurality of waveguides has a width at least 20% greater than a second waveguide of the first plurality of waveguides.

## Claims

### Claim 1

An echelle grating, comprising:
a first interface;
a second interface;
a plurality of output waveguides, at the first interface;
one or more input waveguides, at the second interface; and
a free propagation region connecting the plurality of output waveguides and the one or more input waveguides,
a first waveguide, of the plurality of output waveguides, having a first width,
a second waveguide, of the plurality of output waveguides, having a second width,
the first width being at least 5% greater than the second width,
the echelle grating being configured:
when light is received at a first wavelength in only a third waveguide, of the one or more input waveguides, to direct the light at the first wavelength to the first waveguide; and
when light is received at a second wavelength in only the third waveguide, to direct the light at the second wavelength to the second waveguide, and
a ratio of the first width to the second width being within 10% of a ratio of the first wavelength to the second wavelength.

### Claim 2 (depends on 1)

The echelle grating of claim 1, wherein a trench between the first waveguide and a waveguide, of the plurality of output waveguides, adjacent to the first waveguide has a width less than 1 micron.

### Claim 3 (depends on 2)

The echelle grating of claim 2, wherein the width of the trench is less than 700 nm.

### Claim 4 (depends on 2)

The echelle grating of claim 2, wherein each trench between a pair of adjacent waveguides of the plurality of output waveguides has a width less than 1 micron.

### Claim 5 (depends on 4)

The echelle grating of claim 4, wherein each trench between a pair of adjacent waveguides of the plurality of output waveguides has a width less than 700 nm.

### Claim 6

An echelle grating, comprising:
a first interface;
a second interface;
a plurality of output waveguides, at the first interface;
one or more input waveguides, at the second interface; and
a free propagation region connecting the plurality of output waveguides and the one or more input waveguides,
a first waveguide, of the plurality of output waveguides, having a first width,
a second waveguide, of the plurality of output waveguides, having a second width,
the first width being at least 5% greater than the second width,
the echelle grating being configured:
when light is received at a first wavelength in only a third waveguide, of the one or more input waveguides, to direct the light at the first wavelength to the first waveguide; and
when light is received at a second wavelength in only the third waveguide, to direct the light at the second wavelength to the second waveguide, and
a ratio of the first width to the second width being within 10% of a ratio of the first wavelength to the second wavelength
the first width being selected such that a first field pattern, at a grating of the echelle grating, corresponding to a fundamental mode of the first waveguide, includes, within a range of angles subtended by the grating of the echelle grating, at least 99% of the power of the first field pattern.

### Claim 7 (depends on 6)

The echelle grating of claim 6, wherein the second width is selected such that a second field pattern, at the grating of the echelle grating, corresponding to a fundamental mode of the second waveguide, includes, within a range of angles subtended by the grating of the echelle grating, at least 99% of the power of the second field pattern.