# US 9,882,351 B2 · Laser structure

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- Number: US 9,882,351 B2
- Document ID: US9882351B2
- Status: Granted
- Kind: B2
- Application number: 15/505,836
- Filed: 2015-08-21
- Published: 2017-09-21
- Granted: 2018-01-30
- Earliest claimed: 2014-08-22
- Assignees: The University Court of the University of Glasgow
- Applicants: The University Court of the University of Glasgow
- Inventors: Richard James Edward Taylor; David T. D. Childs; Richard Hogg
- Web page: https://patentgrep.com/patent/US9882351B2

## CPC

- H01S 5/11: Comprising a photonic bandgap structure
- H01S 5/02453: {Heating, e.g. the laser is heated for stabilisation against temperature fluctuations of the environment (H01S5/0612 takes precedence, for monolithically integrated heaters see also H01S5/0261)}
- H01S 5/026: Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers (stabilisation of output H01S5/06)
- H01S 5/042: Electrical excitation {; Circuits therefor (monolithically integrated laser drive components H01S5/0261)}
- H01S 5/1021: {Coupled cavities (H01S5/14 takes precedence)}
- H01S 5/1028: {Coupling to elements in the cavity, e.g. coupling to waveguides adjacent the active region, e.g. forward coupled [DFC] structures}
- H01S 5/18319: {comprising a periodical structure in lateral directions}
- H01S 5/1833: {with more than one structure}
- H01S 5/185: having only horizontal cavities, e.g. horizontal cavity surface-emitting lasers [HCSEL] (comprising a photonic bandgap structure H01S5/11)
- H01S 5/187: using Bragg reflection
- H01S 5/2031: {characterized by special waveguide layers, e.g. asymmetric waveguide layers or defined bandgap discontinuities}
- H01S 5/34366: {based on InGa(Al)AS}
- H01S 5/4012: {Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms}
- H01S 5/42: Arrays of surface emitting lasers
- H01S 5/0608: {controlled by light, e.g. optical switch}
- H01S 5/0612: {controlled by temperature}
- H01S 5/0614: {controlled by electric field, i.e. whereby an additional electric field is used to tune the bandgap, e.g. using the Stark-effect}
- H01S 5/1032: {Coupling to elements comprising an optical axis that is not aligned with the optical axis of the active region}
- H01S 5/2018: {Optical confinement, e.g. absorbing-, reflecting- or waveguide-layers}
- H01S 5/34353: {based on (AI)GaAs}
- H01S 5/3436: {based on InGa(Al)P}
- H01S 5/4075: {Beam steering}
- H01S 5/423: {having a vertical cavity}
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

## Abstract

A laser structure comprising a first photonic crystal surface emitting laser (PCSEL), a second PCSEL, and a coupling region that extends between the first PCSEL and the second PCSEL along a longitudinal axis and that is electrically controllable so as to be capable of coherently coupling the first PCSEL to the second PCSEL. Each PCSEL include an active layer, a photonic crystal, and a two-dimensional periodic array distributed in an array plane parallel to the longitudinal axis within the photonic crystal where the two-dimensional periodic array is formed of regions having a refractive index that is different to the surrounding photonic crystal.

## Claims

### Claim 1

A laser structure comprising:
a first photonic crystal surface emitting laser (PCSEL);
a second PCSEL; and
a coupling region that extends between the first PCSEL and the second PCSEL along a longitudinal axis and that is electrically controllable so as to be capable of coherently coupling the first PCSEL to the second PCSEL;
wherein each PCSEL includes:
an active layer;
a photonic crystal; and
a two-dimensional periodic array distributed in an array plane parallel to the longitudinal axis within the photonic crystal where the two-dimensional periodic array is formed of regions having a refractive index that is different to the surrounding photonic crystal.

### Claim 2 (depends on 1)

The laser structure of claim 1, wherein each PCSEL includes a pair of waveguide cladding layers, and wherein the active layer and photonic crystal of each PCSEL is disposed between the pair of waveguide cladding layers.

### Claim 3 (depends on 2)

The laser structure of claim 2, wherein one or more of the pair of waveguide cladding layers includes one or more distributed Bragg reflectors (DBRs) wherein the one or more DBRs is positioned such that it is in phase with scattered emission from the photonic crystal.

### Claim 4 (depends on 2)

The laser structure of claim 2, wherein the waveguide cladding layers comprise a material having a lower refractive index relative to layers of material intermediate the pair of waveguide cladding layers.

### Claim 5 (depends on 1)

The laser structure of claim 1, wherein the active layer includes quantum wells and/or quantum dots, and optionally includes one or more of lnGaAs/GaAs quantum wells, lnAs/GaAs quantum dots, GaAs/AIGaAs quantum wells, and AllnGaAsP quantum wells.

### Claim 6 (depends on 1)

The laser structure of claim 1, wherein the photonic crystal comprises any suitable semiconductor laser material, and optionally comprises one or more of GaAs, AIGaAs, GalnP, lnGaAs, GalnAsP, AllnGaAs, and AllnGaN.

### Claim 7 (depends on 1)

The laser structure of claim 1, wherein the periodic array is formed of voids in the photonic crystal, or wherein the periodic array is formed of regions of material having a different refractive index relative to the surrounding photonic crystal.

### Claim 8 (depends on 1)

The laser structure of claim 1, wherein the periodic array has a first periodicity along a first direction that is substantially equal to a second periodicity along a second direction that is orthogonal to the first direction, where each of the first and second directions lie along the array plane.

### Claim 9 (depends on 1)

The laser structure of claim 1, wherein the two-dimensional periodic array is a first two-dimensional periodic array, the array plane is a first array plane and the one or more of the PCSELs includes one or more additional two-dimensional periodic arrays distributed in a photonic crystal in an additional array plane that is parallel to the first array plane, optionally wherein the one or more additional two-dimensional periodic array has a different periodicity to the periodicity of the first two-dimensional periodic array.

### Claim 10 (depends on 9)

The laser structure of claim 9, wherein the additional two-dimensional periodic array has a first periodicity along a first direction that is substantially equal to a second periodicity along a second direction that is orthogonal to the first direction, where each of the first and second directions lie along the additional array plane.

### Claim 11 (depends on 1)

The laser structure of claim 1, wherein the coupling region has a modal refractive index that differs from the modal refractive index of the first and second PCSELs by no more than 25%, optionally by no more than 15%, and optionally by no more than 5%.

### Claim 12 (depends on 1)

The laser structure of claim 1, wherein the coupling region is electrically drivable so that an applied current or an applied electric field alters the gain of the coupling region, optionally wherein the coupling region comprises electrodes for applying an electrical current or a voltage across the coupling region.

### Claim 13 (depends on 1)

The laser structure of claim 1, wherein the first and second PCSELs comprise electrodes for applying an electrical current across the first and second PCSELs.

### Claim 14 (depends on 1)

The laser structure of claim 1, further comprising heating apparatus for heating the coupling region, optionally wherein the heating apparatus is configured to heat the coupling region by application of an electrical current or voltage.

### Claim 15 (depends on 14)

The laser structure of claim 14, wherein the coupling region is passive such that there is substantially no absorption or gain at wavelengths corresponding to emitted wavelengths of the active layer of the first and second PCSEL.

### Claim 16 (depends on 1)

The laser structure of claim 1, further comprising one or more PCSELs coupled to the first PCSEL and/or second PCSEL by a second or further electrically controllable coupling region.

### Claim 17 (depends on 1)

The laser structure of claim 1, further comprising an optical arrangement for collecting light emitted from the PCSELs, optionally wherein the optical arrangement is further configured to spatially combine light collected from multiple ones of the PCSELs.

### Claim 18 (depends on 1)

A method of operating a laser structure, comprising:
providing a laser structure according to claim 1;
applying an electrical current to one or more of the PCSELs to operate the one or more PCSELs above their respective lasing thresholds;
electrically controlling the coupler region so as to alter the gain, and/or loss, and/or phase of the coupler region and coherently couple one or more of the PCSELs; and
collecting light emitted from the PCSELs.

### Claim 19 (depends on 18)

The method of claim 18, further comprising spatially combining the collected light.

### Claim 20 (depends on 18)

The method of claim 18, wherein the step of electrically controlling the coupler region comprises applying an electric current to the coupling region, or wherein the step of electrically controlling the coupler region comprises heating the coupling region.