Laser sensor for self-mixing interferometry having a vertical external cavity surface emission laser (VECSEL) as the light source

Patent metadata

Field	Value
Publication number	US-9397476-B2
Application number	US-59821808-A
Country	US
Kind code	B2
Filing date	Apr 29, 2008
Priority date	May 7, 2007
Publication date	Jul 19, 2016
Grant date	Jul 19, 2016

Abstract

The present invention relates to a laser sensor for self-mixing interferometry. The laser sensor comprises at least one semiconductor laser light source emitting laser radiation and at least one photodetector ( 6 ) monitoring the laser radiation of the laser light source. The laser light source is a VECSEL having a gain medium ( 3 ) arranged in a layer structure ( 15 ) on a front side of a first end mirror ( 4 ), said first end mirror ( 4 ) forming an external cavity with an external second end mirror ( 5 ). The proposed laser sensor provides an increased detection range and can be manufactured in a low-cost production process.

First claim

The invention claimed is:

1. A self-mixing interferometric laser sensor comprising:
at least one semiconductor laser light source emitting laser radiation, the laser light source being a vertical external cavity surface emission laser comprising a first end mirror having a front side and a back side, a gain medium arranged in a layer structure on the front side of said first end mirror, the front side of said first end mirror forming an external cavity with an external second end mirror;
and at least one photodetector located on the back side of said front end mirror for measuring changes in properties of subsequent emitted laser radiation; and
wherein several vertical external cavity surface emission lasers with corresponding photodetectors are arranged side by side and form a one or two-dimensional array, said vertical external cavity surface emission lasers being coherently coupled.

2. A laser sensor according to claim 1 , wherein the gain medium is sandwiched between two distributed Bragg reflectors in the layer structure, an outer one of said distributed Bragg reflectors having a higher reflectance for a lasing wavelength than an inner distributed Bragg reflector and forming the first end mirror of said external cavity.

3. A laser sensor according to claim 2 , wherein the layer structure is formed on an optically transparent substrate inside said external cavity.

4. A laser sensor according to claim 2 , wherein the layer structure is formed on a substrate outside said external cavity.

5. A laser sensor according to claim 1 , further comprising a control unit for modulating in time an operating current of the vertical external cavity surface emission laser and to allow operation of the laser with a sawtooth or triangular operating current.

6. A laser sensor according to claim 1 , wherein the external mirror or the layer structure including the first end mirror is mounted on a displacement unit, said displacement unit being controlled by a control unit so as to move said external mirror or said first end mirror for modulating an optical cavity length of the external cavity in time.

7. A laser sensor according to claim 1 , wherein a wavelength tuning unit is arranged between the external mirror and the gain medium, said wavelength tuning unit being controlled by a control unit for modulating in time a central wavelength of the laser radiation emitted by the vertical external cavity surface emission laser.

8. A laser sensor according to claim 7 , wherein the wavelength tuning unit comprises a Fabry-Perot interferometer driven by an actuator.

9. A laser sensor according to claim 7 , wherein the wavelength tuning unit comprises an etalon which is tiltable or rotatable by an actuator.

10. A laser sensor according to claim 1 , wherein the external mirror ( 5 ) of at least one of the several vertical external cavity surface emission lasers comprises a small coupling mirror for deflecting a portion of the laser radiation resonating in the external cavity so as to cause it to pass through the gain medium ( 3 ) of one or several adjacent vertical external cavity surface emission lasers.

11. A self-mixing interferometric laser sensor comprising:
at least one semiconductor laser light source emitting laser radiation, the laser light source being a vertical external cavity surface emission laser comprising a first end mirror having a front side and a back side, a gain medium arranged in a layer structure on the front side of said first end mirror, the front side of said first end mirror forming an external cavity with an external second end mirror; and
at least one photodetector, located on the back side of said front end mirror, for measuring affected subsequent radiation wherein the photodetector is connected to an evaluation unit, said evaluation unit being designed to calculate a distance and/or a velocity associated with the target from measurement signals of the photodetector; and
wherein several vertical external cavity surface emission lasers with corresponding photodetectors are arranged side by side and form a one or two-dimensional array, said vertical external cavity surface emission lasers being coherently coupled.

Assignees

• Baier Johannes
• Moench Holger
• Koninkl Philips Nv

Inventors

• Baier Johannes
• Moench Holger

Classifications

• H01S5/0607

  by varying physical parameters other than the potential of the electrodes, e.g. by an electric or magnetic field, mechanical deformation, pressure, light, temperature · CPC title

• H01S5/141 Primary

  using a wavelength selective device, e.g. a grating or etalon (H01S5/146 takes precedence) · CPC title

• H01S5/0427

  for applying modulation to the laser · CPC title

• H01S5/183

  having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] · CPC title

• H01S5/0264

  for monitoring the laser-output · CPC title