Vertical cavity surface emitting laser

1. A vertical cavity surface emitting laser comprising:

a first electrical contact;

a second electrical contact; and

an optical resonator, the optical resonator comprising:

a first distributed Bragg reflector;

an active layer;

a distributed heterojunction bipolar phototransistor;

a second distributed Bragg reflector; and

an optical guiding structure,

wherein the distributed heterojunction bipolar phototransistor comprises a collector layer, a light sensitive layer, a base layer, and an emitter layer,

wherein the distributed heterojunction bipolar phototransistor is arranged such that there is an optical coupling between the active layer and the distributed heterojunction bipolar phototransistor for providing an active carrier confinement by means of the distributed heterojunction bipolar phototransistor,

wherein the optical guiding structure is arranged to guide an optical mode within the optical resonator of the vertical cavity surface emitting laser during operation of the vertical cavity surface emitting laser, and a position of the optical mode determines a volume in which the distributed heterojunction bipolar phototransistor becomes conductive,

wherein the optical guiding structure is arranged outside a current flow which can be provided by means of the first electrical contact and the second electrical contact during operation of the vertical cavity surface emitting laser,

wherein the optical guiding structure is arranged outside a layer sequence between the first electrical contact and the second electrical contact in the vertical direction of the vertical cavity surface emitting laser, and

wherein the optical guiding structure comprises an oxide aperture, which is arranged in the second distributed Bragg reflector.

2. The vertical cavity surface emitting laser according to claim 1 , wherein a size of the optical guiding structure is smaller than an aperture of at least one of the first electrical contact or the second electrical contact.

3. The vertical cavity surface emitting laser according to claim 1 , wherein the optical guiding structure has a different refractive index than at least one of the first distributed Bragg reflector or the second distributed Bragg reflector.

4. The vertical cavity surface emitting laser according to claim 1 , wherein the vertical cavity surface emitting laser further comprises a current spreading layer, which is directly attached to the first electrical contact or the second electrical contact.

5. The vertical cavity surface emitting laser according claim 4 , wherein the current spreading layer is arranged in a node of a standing wave pattern during operation of the vertical cavity surface emitting laser.

6. The vertical cavity surface emitting laser according claim 5 , wherein the emitter layer comprises the current spreading layer.

7. An optical sensor comprising the vertical cavity surface emitting laser according to claim 1 .

8. A mobile communication device, the mobile communication device comprising at least one optical sensor comprising the vertical cavity surface emitting laser according to claim 1 .

9. A vertical cavity surface emitting laser comprising:

a first electrical contact;

a second electrical contact; and

an optical resonator, the optical resonator comprising:

a first distributed Bragg reflector;

an active layer;

a distributed heterojunction bipolar phototransistor;

a second distributed Bragg reflector; and

an optical guiding structure,

wherein the distributed heterojunction bipolar phototransistor comprises a collector layer, a light sensitive layer, a base layer, and an emitter layer,

wherein the distributed heterojunction bipolar phototransistor is arranged such that there is an optical coupling between the active layer and the distributed heterojunction bipolar phototransistor for providing an active carrier confinement by means of the distributed heterojunction bipolar phototransistor,

wherein the optical guiding structure is arranged to guide an optical mode within the optical resonator of the vertical cavity surface emitting laser during operation of the vertical cavity surface emitting laser,

wherein the optical guiding structure is arranged outside a current flow which can be provided by means of the first electrical contact and the second electrical contact during operation of the vertical cavity surface emitting laser,

wherein the optical guiding structure is arranged outside a layer sequence between the first electrical contact and the second electrical contact in the vertical direction of the vertical cavity surface emitting laser,

wherein the optical guiding structure comprises an oxide aperture, which is arranged in the second distributed Bragg reflector

wherein the optical guiding structure is arranged such that an effective optical length of the optical resonator changes in a defined distance around a center axis of the optical resonator in comparison to the effective optical length of the optical resonator along the center axis,

wherein the effective optical length of the optical resonator along the center axis is longer in comparison to the effective optical length in the defined distance, and

wherein the center axis is perpendicular to the layers building the optical resonator.

10. The vertical cavity surface emitting laser according to claim 9 ,

wherein the optical guiding structure is arranged to reduce the effective optical length of the optical resonator at distances bigger than the defined distance around the center axis of the optical resonator.

11. The vertical cavity surface emitting laser according to claim 10 ,

wherein the optical guiding structure reduces the effective optical length of the optical resonator by means of a reduction of a refractive index of at least one layer of the first distributed Bragg reflector or the second distributed Bragg reflector up to the defined distance.

12. The vertical cavity surface emitting laser according to claim 9 , wherein the optical guiding structure is arranged to increase the effective optical length of the optical resonator up to the defined distance around the center axis of the optical resonator.

13. The vertical cavity surface emitting laser according to claim 12 ,

wherein the optical guiding structure is a phase shift structure, and

wherein the phase shift structure is arranged to increase an effective optical length of the optical resonator up to the defined distance.

14. The vertical cavity surface emitting laser according to claim 13 , wherein the phase shift structure comprises a layer comprising a material selected out of the group comprising SiO 2 , SiN x and a GaAs-based semiconductor.

15. A method of fabricating a vertical cavity surface emitting laser, the method comprising:

providing a first electrical contact;

providing a substrate;

providing a first distributed Bragg reflector;

providing an active layer;

providing a distributed heterojunction bipolar phototransistor comprising a collector layer, a light sensitive layer, a base layer and an emitter layer,

providing a second distributed Bragg reflector;

providing a second electrical contact;

arranging the heterojunction bipolar phototransistor such that there is an optical coupling between the active layer and the heterojunction bipolar phototransistor for providing an active carrier confinement by means of the heterojunction bipolar phototransistor; and

providing an optical guiding structure, wherein the optical guiding structure is arranged to guide an optical mode of the vertical cavity surface emitting laser during operation of the vertical cavity surface emitting laser, and a position of the optical mode determines a volume in which the distributed heterojunction bipolar phototransistor becomes conductive,

wherein the optical guiding structure is arranged outside a current flow which can be provided by means of the first electrical contact and the second electrical contact during operation of the vertical cavity surface emitting laser,

wherein the optical guiding structure is arranged outside a layer sequence between the first electrical contact and the second electrical contact in the vertical direction of the vertical cavity surface emitting laser, and

wherein the optical guiding structure comprises an oxide aperture which is arranged in the second distributed Bragg reflector.