A self-mixing interferometric, SMI, laser sensor comprises a vertical cavity surface emitting laser, VCSEL, configured to emit laser radiation, the VCSEL comprising a first distributed Bragg reflector, DBR, a second DBR and a cavity region including an active light generation region, wherein the cavity region is arranged in a layer structure between a front side of the first DBR and a back side of the second DBR. Therein at least one of the first and second DBR comprises a first contrast region and a second contrast region, the first contrast region having a first refractive index contrast n.sub.1 regarding an emission wavelength of the VCSEL and the second contrast region having a second refractive index contrast n.sub.2/n larger than the first refractive index contrast n.sub.1/n.

A self-mixing interferometry sensor module, comprising a light emitter (LE), a detector unit (DU) and an optical element (OE), wherein the light emitter (LE) is operable to emit coherent electromagnetic radiation towards an external object (ET) to be placed outside the sensor module and undergo self-mixing interference, SMI, caused by reflections of the emitted electromagnetic radiation from the external object back inside the sensor module. The detector unit (DU) is operable to generate output signals indicative of an optical power output of the light emitter (LE) due to the SMI. The optical element (OE) is aligned with respect to the light emitter (LE) such that a first fraction of electromagnetic radiation is directed towards the external target (ET) or the light emitter (LE) and a second fraction of electromagnetic radiation is directed towards the detector unit (DU). An optical power ratio determined by the first and second fractions meets a pre-determined value.

An optical sensor system includes a set of epitaxial layers formed on a semiconductor substrate. The set of epitaxial layers defines a semiconductor laser having a first multiple quantum well (MQW) structure. Electromagnetic radiation is generated by the first MQW structure, emitted from the first MQW structure, and self-mixed with a portion of the emitted electromagnetic radiation that is returned to the first MQW structure. The set of epitaxial layers also defines a second MQW structure operable to generate a first photocurrent responsive to detecting a first emission of the semiconductor laser, and a third MQW structure operable to generate a second photocurrent responsive to detecting a second emission of the semiconductor laser. The optical sensor system also includes a circuit configured to generate a self-mixing interferometry (SMI) signal by combining the first photocurrent and the second photocurrent.

A system and method for generating, enhancing, and detecting the amplitude and phase modulation of a laser under a condition of self-mixing is provided. The system may comprise a laser and a detector to extract the characteristic self-mix signal, which is then interpreted using algorithms implemented in hardware or software. In the case of the laser being a Vertical Cavity Surface Emitting laser (VCSEL), the output signal can be detected by monitoring the surface light emission by means of a beam splitter, or in some embodiments as emission from the bottom surface of the laser. In some embodiments, the system may further comprise a wavelength filter such as an etalon in the signal path.

An electronic device such as an earbud may have control circuitry mounted in a housing. The housing may have portions such as an ear portion with a speaker port through which a speaker plays audio and a stalk portion that extends from the ear portion. Proximity sensors may be formed in the electronic device. For example, one or more proximity sensors may be formed on the ear portion to detect when a user has inserted an earbud into the ear of the user and/or one or more proximity sensors may be formed on a stalk portion to detect when a user is holding an earbud by the stalk or when a user is providing finger touch input such as taps, swipes, and/or other gestures on the stalk portion. The proximity sensors may be optical proximity sensors such as coherent self-mixing proximity sensors.

The present invention relates to a method and an apparatus for measuring the properties of a liquid that exploit the power modulation a laser light beam undergoes due to the retro-reflection of the laser light beam itself towards the laser cavity from which the laser is generated when this laser light is directed towards a transparent conduit through which the liquid for which the properties are to be measured flows.

According to the invention this power modulation is detected by at least one photodiode arranged downstream of the transparent conduit.

The invention describes a laser sensor or laser sensor module (100) using self-mixing interference for particle density detection, a related method of particle density detection and a corresponding computer program product. The invention further relates to devices comprising such a laser sensor or laser sensor module. It is a basic idea of the present invention to detect particles by means of self-mixing interference signals and determine a corresponding particle density. In addition at least a first parameter related to at least one velocity component of a velocity vector of the particles is determined in order to correct the particle density if there is the relative movement between a detection volume and the particles. Such a relative movement may for example be related to a velocity of a fluid transporting the particles (e.g. wind speed). Furthermore, it is possible to determine at least one velocity component of the velocity of the particles based on the self-mixing interference signals.

The invention describes a laser sensor module (100) which is adapted to detect or determine at least two different physical parameters by means of self-mixing interference by focusing a laser beam to different positions. Such a laser sensor module (100) may be used as an integrated sensor module, for example, in mobile devices (250). The laser sensor module (100) may be used as an input device and in addition as a sensor for detecting physical parameters in an environment of the mobile communication device (250). One physical parameter in the environment of the mobile communication device (250) may, for example, be the concentration of particles in the air (air pollution, smog . . . ). The invention further describes a related method and computer program product.

A vertical cavity surface emitting laser includes an optical resonator, a photodiode, and an electrical contact arrangement. The optical resonator includes a semiconductor multilayer stack. The semiconductor multilayer stack includes, in a direction of growth of the multilayer stack, a first distributed Bragg reflector, a second distributed Bragg reflector, and an active region for laser emission arranged between the first distributed Bragg reflector and second distributed Bragg reflector. The electrical contact arrangement is arranged to electrically pump the optical resonator and to electrically contact the photodiode. A reflectivity of the second distributed Bragg reflectoris higher than a reflectivity of the first distributed Bragg reflector. The photodiode has an absorbing region arranged in the second distributed Bragg reflector. A tunnel junction is arranged between the photodiode and the active region.

The invention describes a laser sensor module. The laser sensor module comprises at least one laser (100) being adapted to emit a measurement beam (111). The laser sensor module further comprises a compact optical device (150) being arranged to focus the measurement beam (111) to a focus region (115). The compact optical device comprises an optical carrier (154) with a convex mirror surface (152) on one side and a concave mirror surface (156) on a second opposite side, wherein the concave mirror surface (156) comprises an entrance surface through which the measurement beam (111) can enter the optical carrier (154). The compact optical device (150) is arranged such that the measurement beam (111) entering the optical carrier is reflected and diverged by means of the convex mirror surface (152) to the concave mirror surface (156). The concave mirror surface (156) is arranged to focus the measurement beam (111) received from the convex mirror surface (152) to a focus region (115). The laser sensor module further comprises at least one detector (120) which is adapted to determine at least a self-mixing interference signal of a first optical wave within a laser cavity of the laser (100).The invention further describes a laser sensor (180) comprising such a laser sensor module. The invention finally describes devices like a mobile communication device comprising the laser sensor (180) or the laser sensor module.