# US 2015/0146212 A1 · Surface emitting laser and optical coherence tomography apparatus including the same

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- Number: US 2015/0146212 A1
- Document ID: US20150146212A1
- Status: Published application
- Kind: A1
- Application number: 14/552,019
- Filed: 2014-11-24
- Published: 2015-05-28
- Earliest claimed: 2013-11-27
- Assignees: Canon Kabushiki Kaisha
- Applicants: Canon Kabushiki Kaisha
- Inventors: Toshimitsu Matsuu; Takeshi Uchida
- Web page: https://patentgrep.com/patent/US20150146212A1

## CPC

- G01B 9/02091: Tomographic interferometers, e.g. based on optical coherence
- G01B 9/02004: using frequency scans
- H01S 5/11: Comprising a photonic bandgap structure
- H01S 5/18366: {Membrane DBR, i.e. a movable DBR on top of the VCSEL}
- H01S 5/18369: {based on dielectric materials}
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- 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 surface emitting laser includes a lower reflector, an active layer, a gap portion, an upper reflector, and a driving unit. The lower reflector, the active layer, the gap portion, and the upper reflector are arranged in that order. The surface emitting laser is capable of varying a wavelength of emitted light by changing a distance between the upper and lower reflectors. The driving unit moves one of the upper and lower reflectors in an optical axis direction of the emitted light. At least one of the upper and lower reflectors includes a stacked body in which first layers and second layers are alternately stacked, the second layers having a refractive index lower than a refractive index of the first layers, outermost layers of the stacked body being the first layers, and a third layer provided on at least one end of the stacked body.

## Claims

### Claim 1

A surface emitting laser comprising:
a lower reflector;
an active layer;
a gap portion;
an upper reflector; and
a driving unit,
wherein the lower reflector, the active layer, the gap portion, and the upper reflector are arranged in that order,
wherein the surface emitting laser is capable of varying a wavelength of emitted light by changing a distance between the upper and lower reflectors,
wherein the driving unit moves one of the upper and lower reflectors in an optical axis direction of the emitted light, and
wherein at least one of the upper and lower reflectors includes
a stacked body in which first layers and second layers are alternately stacked, the second layers having a refractive index lower than a refractive index of the first layers, outermost layers of the stacked body being the first layers, and
a third layer provided on at least one end of the stacked body and configured such that an optical thickness nd of the third layer satisfies 0<nd<λ0/2, where λ0 is a center wavelength of the emitted light, the third layer having a refractive index that is lower than the refractive index of the first layers and higher than a refractive index of a layer provided adjacent to the third layer at a side opposite to a side at which the stacked body is provided.

### Claim 2 (depends on 1)

The surface emitting laser according to claim 1, wherein the layer provided adjacent to the third layer is air.

### Claim 3 (depends on 1)

The surface emitting laser according to claim 1, wherein the optical thickness nd satisfies λ0/8<nd<3λ0/8.

### Claim 4 (depends on 1)

The surface emitting laser according to claim 1, wherein the optical thickness nd is λ0/4.

### Claim 5 (depends on 1)

The surface emitting laser according to claim 1, wherein a reflectance of the stacked body with respect to the center wavelength λ0 is 99.5% or more.

### Claim 6 (depends on 1)

The surface emitting laser according to claim 1, wherein the stacked body includes 35 or more pairs of layers, each pair including one of the first layers and one of the second layers.

### Claim 7 (depends on 1)

The surface emitting laser according to claim 1, wherein the first layers, the second layers, and the third layer are all semiconductor layers.

### Claim 8 (depends on 7)

The surface emitting laser according to claim 7, wherein each of the semiconductor layers includes a material expressed as AlxGa(1-x)As (0≦x≦1).

### Claim 9 (depends on 1)

The surface emitting laser according to claim 1, wherein the driving unit moves the upper reflector.

### Claim 10 (depends on 1)

The surface emitting laser according to claim 1, wherein the upper reflector is a diffraction grating.

### Claim 11 (depends on 1)

The surface emitting laser according to claim 1, wherein the driving unit moves the lower reflector.

### Claim 12 (depends on 1)

The surface emitting laser according to claim 1, wherein the lower reflector includes the stacked body.

### Claim 13 (depends on 1)

The surface emitting laser according to claim 1, wherein the third layer is provided on one end of the stacked body.

### Claim 14 (depends on 1)

The surface emitting laser according to claim 1, wherein the third layer is provided on each end of the stacked body.

### Claim 15 (depends on 1)

The surface emitting laser according to claim 1, wherein the active layer emits light when the active layer is excited by being irradiated with light.

### Claim 16 (depends on 1)

The surface emitting laser according to claim 1, wherein the active layer emits light when a current is applied to the active layer.

### Claim 17

A surface emitting laser comprising:
a lower reflector;
an active layer;
an upper reflector; and
a gap portion disposed between the active layer and the upper reflector,
wherein the lower reflector, the active layer, and the upper reflector are arranged in that order,
wherein the surface emitting laser is capable of varying a wavelength of emitted light by changing a distance between the upper and lower reflectors,
wherein at least one of the upper and lower reflectors serves as a reflector from which the light is emitted and includes a stacked body in which first layers and second layers are alternately stacked, the second layers having a refractive index lower than a refractive index of the first layers, and
wherein the stacked body is provided with a reflection suppressing layer.

### Claim 18 (depends on 1)

An optical coherence tomography apparatus comprising:
a light source unit that varies a wavelength of light;
an interference optical system that divides the light from the light source into irradiation light with which an object is to be irradiated and reference light and generates interference light by causing reflected light of the irradiation light with which the object has been irradiated and the reference light to interfere with each other;
a light detecting unit that receives the interference light; and
an information acquisition unit that acquires information of the object by processing a signal from the light detecting unit,
wherein the light source unit is the surface emitting laser according to claim 1.

### Claim 19 (depends on 18)

The apparatus according to claim 18, wherein the optical thickness nd satisfies λ0/8<nd<3λ0/8.

### Claim 20 (depends on 18)

The apparatus according to claim 18, wherein the optical thickness nd is λ0/4.