Photonic crystal surface emitting laser diode for self-mixing interference or frequency modulated continuous wave sensing and related device

Abstract

A photonic crystal surface emitting laser diode and related devices relating to self-mixing interference or frequency modulated continuous wave sensing. Relates to an SMI sensor, an FMCW sensor and an electronic device comprising the SMI sensor and the FMCW sensor. Both types of sensors include photonic crystal surface emitting laser diodes. The SMI sensor includes a photonic crystal surface emitting laser diode configured to undergo SMI between primary emitted light from the photonic crystal surface emitting laser diode and its reflection from an object. The SMI sensor includes a photodetector configured to receive secondary light emission from the photonic crystal surface emitting laser diode and to detect a parameter related to the SMI from which distance or motion to the object may be inferred. The FMCW sensor includes a photonic crystal surface emitting laser diode configured to emit a primary light emission toward an object and a secondary light emission toward a beam combiner. The beam combiner also receives reflections from the object and detects the distance and / or motion of the object based on the frequency modulation of the two beams.

Description

Technical Field

[0001] The present disclosure as a whole relates to laser diodes such as photonic crystal surface emitting laser diodes, and associated photodetectors. Examples of photonic crystal surface emitting laser diodes include any laser diode having a photonic crystal layer, such as a photonic cavity surface emitting laser diode (PCSEL) and a topological cavity surface emitting laser diode (TCSEL). For the remainder of this specification, references to PCSELs are understood as references to any type of photonic crystal surface emitting laser diode (e.g., PCSEL or TCSEL).

[0002] The present disclosure also relates to sensor devices including such PCSELs. The laser diode and associated photodetector may be configured such that self-mixing interference (SMI) is used to sense or detect an object. Additionally and / or alternatively, the laser diode and associated photodetector may be configured such that frequency modulated continuous wave (FMCW) sensing is used to sense or detect an object.

[0003] PCSELs or other laser diodes may be used in sensor devices, such as digital cameras or light detection and ranging (LIDAR) devices, etc. These devices may include arrays of PCSELs or other laser diodes and associated photodetectors. Background Art

[0004] Electronic devices with light transmitting and sensing systems are common in today's society. Example electronic devices include cellular phones and computers with cameras, stand-alone cameras, LIDAR systems, facial recognition security systems, etc. Some of these electronic devices include laser diodes, such as vertical surface emitting laser diodes (VCSELs), edge emitting laser diodes (EELs), vertical external cavity emitting laser diodes (VECSELs), or other types of laser diodes. The laser diodes can be arranged in an array, such as on a semiconductor chip. The electronic device can cause such component laser diodes to emit light from the electronic device toward an object in the external environment of the electronic device. The emitted light can be pulsed or continuous, and can be provided in a flood, spot, or pattern form.

[0005] The electronic device may also include one or more photodetectors (PDs) configured to receive reflections of the emitted laser from an object. The type of photodetector may be a complementary metal oxide semiconductor (CMOS) PD, a single photon avalanche diode (SPAD), a resonant cavity photodetector (RCPD), or other types of photodetectors. In some embodiments, the PD array may be provided separately from the laser diode array. Alternatively, the PD array may be integrated with the laser diode array (e.g., interspersed or stacked with the laser diode array).

[0006] The electronic device may estimate the distance to the object based on the received reflection of the transmitted laser light by any of a variety of methods including, but not limited to, time-of-flight (TOF) sensing, SMI sensing, FMCW sensing, or other sensing methods.

[0007] Based on the estimated distance to the object (or objects), the electronic device may form a depth map or image of the object, which may then be used for autofocus, facial recognition, motion detection, surface mapping, hazard avoidance, or other purposes. Summary of the invention

[0008] This summary is provided to introduce a series of concepts in a simplified form, which are further described in the detailed description below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0009] Disclosed herein are electronic devices, systems, and various components thereof that emit light and detect properties of objects in an environment based on received reflections of the emitted light. The electronic devices, systems, and components may include light emitting laser diodes and photodetectors. Examples of such electronic devices and systems include LIDAR systems and cameras in smartphones, among others.

[0010] More specifically, the first class of embodiments discloses a self-mixing interferometry (SMI) sensor, which includes a photonic crystal light emitting laser diode and an associated photodetector disposed on a substrate. The photonic crystal light emitting laser diode is configured to emit light once through the substrate toward an object in the environment of the SMI sensor. The photonic crystal light emitting laser diode includes a photonic crystal layer, an active region, and a first semiconductor cladding layer and a second semiconductor cladding layer. The active region is disposed between the photonic crystal layer and the substrate, has a primary emission side, through which a primary light emission occurs, the first semiconductor cladding layer is disposed on the primary emission side of the active region and is disposed between the active region and the substrate, and the second semiconductor cladding layer is disposed on the secondary light emission side of the active region, wherein the secondary light emission side is opposite to the primary emission side, and the photonic crystal layer is disposed between the second semiconductor cladding layer and the active region. The SMI sensor also includes a distributed Bragg reflector (DBR), which is disposed on the second semiconductor cladding layer, so that the second semiconductor cladding layer is disposed between the DBR and the photonic crystal layer. An associated photodetector is positioned proximate to the DBR and is configured to receive secondary light emission emitted from the photonic crystal surface emitting laser diode through the second semiconductor cladding layer and the DBR, wherein the photodetector is configured to produce a measurable electrical parameter related to self-mixing of light within the photonic crystal surface emitting laser diode. The photonic crystal layer may have a planar pattern of voids.

[0011] In some embodiments, the DBR of the SMI sensor can be a first DBR, and the photodetector includes: a photodetector absorption layer, which is adjacent to the first DBR and opposite to the second semiconductor cladding layer; and a second DBR, which is adjacent to the photodetector absorption layer and opposite to the first DBR.

[0012] In some embodiments, the photonic crystal surface emitting laser diode and the photodetector include epitaxial layers on a substrate, and the measurable electrical parameter associated with self-mixing is a photocurrent of the photodetector.

[0013] In some embodiments, the photodetector is spaced apart from the DBR, and the photodetector is electrically connected to the DBR through a metal link between at least a first electrode on the DBR and at least a second electrode on the photodetector.

[0014] The second class of embodiments discloses a frequency modulated continuous wave (FMCW) sensor, which includes: a semiconductor current distribution layer; a photonic crystal surface emitting laser diode, which is disposed on the semiconductor current distribution layer and is configured to perform a primary light emission through the semiconductor current distribution layer; a distributed Bragg reflector (DBR); a semiconductor substrate layer; a beam combiner; and an optoelectronic circuit. The photonic crystal surface emitting laser diode includes: a photonic crystal layer; an active region, which is disposed between the photonic crystal layer and the semiconductor current distribution layer and has a primary emission side, through which a primary light emission occurs; a first semiconductor cladding layer, which is disposed on the primary emission side of the active region and disposed between the active region and the semiconductor current distribution layer; and a second semiconductor cladding layer, which is disposed on the secondary light emission side of the active region, the secondary light emission side is opposite to the primary emission side, and the photonic crystal layer is disposed between the second semiconductor cladding layer and the active region. The DBR is disposed on the second semiconductor cladding layer, so that the second semiconductor cladding layer is disposed between the DBR and the photonic crystal layer. The semiconductor substrate layer is disposed adjacent to the DBR and opposite to the second semiconductor cladding layer. The beam combiner is positioned across a gap with the semiconductor substrate layer of the photonic crystal surface emitting laser diode PCSEL and is configured to generate a FMCW optical output by combining reflection of a primary light emission emitted from a primary emission side of the active region and a secondary light emission emitted from a secondary light emission side of the active region, the secondary light emission being emitted through the semiconductor substrate layer. The optoelectronic circuit is configured to receive the FMCW optical output and generate a measurable electrical parameter related to the modulation of the FMCW optical output.

[0015] In some embodiments, the semiconductor current distribution layer has n-type doping, the first semiconductor cladding layer has n-type doping, the second semiconductor cladding layer has p-type doping, the DBR has p-type doping, and the semiconductor substrate layer has n-type doping and is one of gallium arsenide (GaAs), indium phosphide (InP), or another semiconductor (such as a III-V semiconductor). The FMCW sensor may also include a tunnel junction. The photonic crystal surface emitting laser diode FMCW sensor may include at least one on-chip lens positioned on the semiconductor substrate layer and configured to direct the secondary light emission to the beam combiner.

[0016] The beam combiner of the FMCW sensor may also include: a first metasurface configured to combine the reflection of the primary light emission with the secondary light emission and produce a first combined output; and a second metasurface configured to combine the reflection of the primary light emission with the secondary light emission and produce a second combined output. The optoelectronic circuit may include: a first photodetector positioned to receive the first combined output; a second photodetector positioned to receive the second combined output light; and an amplifier configured to receive both the electrical output of the first photodetector and the electrical output of the second photodetector.

[0017] A third class of embodiments discloses an electronic device comprising: an array of photonic crystal surface emitting laser diodes, each photonic crystal surface emitting laser diode being operable to emit a single light emission from the photonic crystal surface emitting laser diode through a light emitting surface of the electronic device toward one or more objects outside the electronic device; a photodetector array, the photodetector array being configured to receive at least a secondary light emission emitted from the photonic crystal surface emitting laser diode in the array of photonic crystal surface emitting laser diodes toward the photodetector array; and an electronic circuit configured to receive a measurable output signal from a photodetector in the photodetector array. Each photonic crystal surface emitting laser diode in the photonic crystal surface emitting laser diode array includes: an n-doped current distribution layer, which is close to the light emitting surface of the electronic device, and a primary light emission is emitted from the electronic device through the light emitting surface; an n-type cladding layer, which is adjacent to the n-doped current distribution layer and opposite to the light emitting surface of the electronic device; an active region, which is adjacent to the n-type cladding layer and opposite to the semiconductor substrate layer; a photonic crystal layer, which is adjacent to the active region and opposite to the n-type cladding layer; a p-type cladding layer, which is adjacent to the photonic crystal layer and opposite to the active region; and a p-type distributed Bragg reflector (DBR) layer, which is adjacent to the p-type cladding layer and opposite to the photonic crystal layer.

[0018] In some embodiments, the photonic crystal surface emitting laser diodes in the photonic crystal surface emitting laser diode array are individually addressable by electronic circuitry.

[0019] In some embodiments, electronic circuitry of an electronic device is operable to generate a depth map of one or more objects external to the electronic device using measurable output signals from photodetectors in a photodetector array.

[0020] In some embodiments, the photodetectors in the photodetector array include a photodetector absorption layer, and the photodetectors in the photodetector array generate an output signal that is related to self-mixing interference of secondary light emissions and reflections of primary light emissions from one or more objects outside the electronic device, and the output signal related to the self-mixing interference is included in a measurable output signal used by the electronic device to generate a depth map.

[0021] In some embodiments, the photodetectors in the photodetector array include a pair of separated and balanced semiconductor photodetectors having corresponding metasurfaces, the metasurfaces being configured to combine secondary light emissions with reflections of primary light emissions from one or more objects external to the electronic device, and the pair of separated and balanced semiconductor photodetectors generating corresponding output photocurrents related to frequency modulation between the combined primary and secondary light emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present disclosure will be more easily understood through the following detailed description in conjunction with the accompanying drawings, in which like reference numerals represent like structural elements.

[0023] Figure 1A and Figure 1B Examples are shown of devices that may include one or more of an image sensor, camera, photosensor, or depth / range sensor that may utilize embodiments disclosed herein.

[0024] Figure 1C is a simplified block diagram of a LIDAR system that may utilize embodiments disclosed herein.

[0025] Figure 2A An exploded view of certain components of a PCSEL is shown according to one embodiment.

[0026] Figure 2B Shown is a top view of a photonic crystal layer of a PCSEL according to one embodiment.

[0027] Figure 3 A cross-sectional view of a PCSEL coupled to a PD according to one embodiment is shown.

[0028] Figure 4A cross-sectional view of a PCSEL separated from a PD by a gap is shown according to one embodiment.

[0029] Figure 5A A cross-sectional view of a PCSEL and associated light combining components is shown according to one embodiment.

[0030] Figure 5B According to one embodiment, Figure 5A Doping configuration of the PCSEL tunnel junction.

[0031] Figure 5C According to one embodiment, Figure 5A An electrical component associated with an optical combination component.

[0032] Figure 5D According to one embodiment, Figure 5A A specific embodiment of the light combination component.

[0033] Figure 6 A block diagram of an electronic device that may include one or more of the embodiments described herein is shown.

[0034] The use of cross-hatching or shading in the drawings is generally provided to clarify boundaries between adjacent elements and also to facilitate legibility of the drawings. Thus, the presence or absence of cross-hatching or shading does not express or indicate any preference or requirement for particular materials, material properties, element proportions, element sizes, commonality of similar illustrated elements, or any other feature, attribute, or characteristic of any element shown in the drawings.

[0035] Additionally, it should be understood that the proportions and sizes (relative or absolute) of the various features and elements (and collections and groupings thereof) and the boundaries, spacings, and positional relationships presented therebetween are provided in the accompanying drawings solely to facilitate understanding of the various embodiments described herein, and therefore may not necessarily be presented or illustrated to scale and are not intended to indicate any preference or requirement for the embodiments illustrated to exclude the embodiments described in conjunction therewith. DETAILED DESCRIPTION

[0036] Reference will now be made in detail to the representative embodiments illustrated in the accompanying drawings. It should be understood that the following description is not intended to limit the embodiments to a preferred embodiment. On the contrary, it is intended to cover substitutions, modifications and equivalents that may be included within the spirit and scope of the described embodiments defined by the appended claims.

[0037] In addition, although specific electronic devices are shown in the figures and described below, the SMI sensors and FMCW sensors and PCSEL structures described herein can be used with a variety of electronic devices, including but not limited to mobile phones, personal digital assistants, timing devices, health monitoring devices, wearable electronic devices, input devices (e.g., stylus), desktop computers, electronic glasses, etc. Other examples and specific implementations are within the scope and spirit of the present disclosure and the appended claims. Although various electronic devices are mentioned, the present disclosure can also be used in conjunction with other products and in combination with various materials.

[0038] Directional terms, such as "top", "bottom", "upper", "lower", "front", "rear", "above", "below", "above", "below", "left", "right", etc., are used with reference to the orientation of some components in some of the figures described below. Since components in various embodiments can be positioned in a plurality of different orientations, the directional terms are used for illustrative purposes only and are not necessarily limiting. Directional terms are intended to be interpreted broadly and therefore should not be interpreted to exclude components oriented in different ways. In addition, as used herein, the phrase "at least one of" following a series of items in the items separated by the terms "and" or "or" is to modify the list as a whole, rather than modifying each member of the list. The phrase "at least one of" does not require selection of at least one of each of the listed items; rather, the phrase allows for the meaning of including at least one of any of the items in the items and / or at least one of any combination of the items and / or at least one of each of the items in the items. For example, the phrase "at least one of A, B, and C" or "at least one of A, B, or C" each refers to only A, only B, or only C; any combination of A, B, and C; and / or one or more of each of A, B, and C. Similarly, it should be understood that the order in which elements are presented for either a combined or separate list provided herein should not be construed to limit the present disclosure to only the order provided.

[0039] Embodiments described herein relate to electronic devices or systems that include SMI sensors or FMCW sensors. SMI sensors and FMCW sensors include one or more PCSEL structures and associated PDs. Examples of such devices or systems that use such SMI sensors or FMCW sensors include LIDAR systems, object detection and mapping systems on self-driving cars, cameras on computers or cell phones, and other electronic devices.

[0040] The described SMI sensors and FMCW sensors use emitted laser light in combination with its reflection to detect or sense an object or property thereof external to the sensor. The sensor may be configured to detect the distance or range of one or more objects external to the device and / or the motion or speed of the objects. An electronic device may include an array of such SMI sensors and / or FMCW sensors.

[0041] The sensors described herein may include one or more PCSELs. (Hereinafter, the acronyms of the various types of laser diodes mentioned will be assumed to be the word "diode"). The PCSEL may be configured to generate and emit laser light in a first direction toward an object, referred to as a primary light emission, and also emit the generated laser light in a direction opposite (or different) to the primary light emission, referred to as a secondary light emission. The reflection of the primary light emission from the object may be received in the sensor and may be combined with the primary light emission or the secondary light emission. The characteristics of the combined light (wavelength, phase, modulation, frequency, etc.) may generate signals in components of the sensor, which the sensor or device may then use to estimate the distance or motion of one or more objects. The PCSEL described herein may include a photonic crystal layer having a patterned photonic crystal structure. Such a patterned photonic crystal structure includes (for a photonic crystal layer with a thickness much smaller than the lateral dimension) a planar pattern in the lateral dimension of the cavity, or a planar pattern of two or more materials with different refractive indices. The patterned photonic crystal structure may also have a three-dimensional pattern of materials with different refractive indices.

[0042] The first and second classes of embodiments utilize SMI that occurs within the lasing cavity of a PCSEL between a primary light emission and a reflection received from an object back into the lasing cavity of the PCSEL. The SMI causes a change in the properties of the emitted laser light. The extent of the change caused by the SMI may be related to the distance to the object. The change from unmixed emitted light to SMI emitted light may produce corresponding changes in electrical parameters or other parameters of the PCSEL, such as changes in junction voltage, diode current, or another parameter, which may be measured by electrical components associated with the PCSEL. Additionally or alternatively, the secondary light emission from the PCSEL may be SMI emitted light directed to a photodetector, which may have a measurable parameter related to the change caused by the SMI.

[0043] In a first class of embodiments, the PCSEL is coupled to a photodetector such as a photodiode, which is positioned on a side opposite to the side from which the primary light emission is emitted. In some embodiments, the photodiode detector may be configured as a resonant cavity photodiode (RCPD). In these embodiments, the PCSEL may also emit secondary light emissions toward the RCPD, which may have a measurable parameter related to the SMI. In a first class of embodiments, the RCPD and the PCSEL may be formed on a single semiconductor substrate, for example, by epitaxial deposition or other techniques.

[0044] The second class of embodiments also utilizes the SMI that occurs between the primary emission light and the reflection received from the object back into the PCSEL's lasing cavity within the PCSEL. In the second class of embodiments, the PCSEL structure may include a distributed Bragg reflector (DBR) bonded to a photonic crystal layer. The DBR is a structure formed by multiple alternating layers of materials with different refractive indices that can provide full or partial reflectivity. In this class of embodiments, the photodetector may be separated from the PCSEL and DBR structures and may receive secondary light emissions that have been altered by the SMI. The photodetector in such embodiments may be a photodiode, an RCPD, a CMOS photodetector, or another photodetector.

[0045] The third class of embodiments utilizes FMCW mixing of reflection of the primary light emission with secondary light emission from the PCSEL. The secondary light emission may be directed in the opposite direction of the primary light emission to a beam combiner that is separate from the PCSEL structure. In these embodiments, the PCSEL may include a DBR coupled to the PCSEL. The secondary light emission from the PCSEL may be modulated in wavelength, such as by changing the voltage applied to the PCSEL, and combined with the reflection of the primary light emission at the beam combiner to produce frequency modulated light that is input to the PD.

[0046] In some embodiments of the beam combiner, there are two separate balanced PDs, each including a metasurface that receives and combines both the secondary light emission and the reflection of the primary light emission. The output of each PD can be an input to a differential amplifier and subsequent signal processing components.

[0047] In additional and / or alternative embodiments, a beam combiner can combine the secondary light emission with the reflection of the primary light emission into a combined light beam, which can be input into a fiber optic cable or waveguide. A beam splitter can then provide an equal (50 / 50 split) combined light beam to a balanced photodetector that provides frequency modulated continuous wave detection followed by subsequent signal processing.

[0048] References below Figures 1A to 6 These and other embodiments are discussed. However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for illustration purposes only and should not be construed as limiting.

[0049] Figure 1A and Figure 1BAn example of a device 100 that may include an image sensor or a depth sensor is shown. The size and form factor of the device (including the ratio of the length of its long side to the length of its short side) indicate that the device 100 is a mobile phone (e.g., a smart phone). However, the size and form factor of the device are arbitrarily selected, and the device 100 may alternatively be any portable electronic device, including, for example, a mobile phone, a tablet computer, a portable computer, a portable music player, a wearable device (e.g., an electronic watch, a health monitoring device, or a fitness tracking device), an augmented reality (AR) device, a virtual reality (VR) device, a mixed reality (MR) device, a gaming device, a portable terminal, a digital single-lens reflex (DSLR) camera, a video camera, a vehicle navigation system, a robot navigation system, or other portable or mobile devices. The device 100 may also be a device that is semi-permanently located (or installed) at a single location. Figure 1A A front isometric view of the device 100 is shown, and Figure 1B A rear isometric view of the device 100 is shown. The device 100 may include a housing 102 that at least partially surrounds a display 104. The housing 102 may include or support a front cover 106 or a back cover 108. The front cover 106 may be positioned above the display 104 and may provide a window through which the display 104 may be viewed. In some embodiments, the display 104 may be attached to (or adjacent to) the housing 102 and / or the front cover 106. In alternative embodiments of the device 100, the display 104 may not be included and / or the housing 102 may have an alternative configuration.

[0050] The display 104 may include one or more light emitting elements, and in some cases may be a light emitting diode (LED) display, an organic LED (OLED) display, a liquid crystal display (LCD), an electroluminescent (EL) display, or another type of display. In some embodiments, the display 104 may include or be associated with one or more touch sensors and / or force sensors configured to detect touch and / or force applied to the surface of the front cover 106.

[0051] Various components of the housing 102 may be formed of the same or different materials. For example, the sidewall 118 of the housing 102 may be formed using one or more metals (e.g., stainless steel), polymers (e.g., plastics), ceramics, or composite materials (e.g., carbon fiber). In some cases, the sidewall 118 may be a multi-segment sidewall including a set of antennas. The antenna may form a structural component of the sidewall 118. The antenna may be structurally coupled (to each other or to other components) and electrically isolated (to each other or to other components) by one or more non-conductive segments of the sidewall 118. The front cover 106 may be formed, for example, using one or more of glass, crystal (e.g., sapphire), or a transparent polymer (e.g., plastic), which enables a user to view the display 104 through the front cover 106. In some cases, a portion of the front cover 106 (e.g., a peripheral portion of the front cover 106) may be coated with an opaque ink to cover the components included in the housing 102. The back cover 108 may be formed using the same material as that used to form the sidewall 118 or the front cover 106. In some cases, back cover 108 may be part of an integral element that also forms sidewall 118 (or those portions of sidewall 118 that are conductive or non-conductive if sidewall 118 is a multi-segment sidewall). In other embodiments, all exterior components of housing 102 may be formed of a transparent material, and components within device 100 may or may not be covered by an opaque ink or opaque structure within housing 102.

[0052] The front cover 106 can be mounted to the side wall 118 to cover the opening defined by the side wall 118 (i.e., the opening into the interior volume where the various electronic components of the device 100 (including the display 104) can be located). The front cover 106 can be mounted to the side wall 118 using fasteners, adhesives, seals, gaskets, or other components.

[0053] A display stack or device stack (hereinafter referred to as the "stack") including display 104 can be attached (or adjacent) to the inner surface of front cover 106 and extend into the interior volume of device 100. In some cases, the stack can include a touch sensor (e.g., a grid of capacitive, resistive, strain-based, ultrasonic, or other types of touch sensing elements) or other layers of optical, mechanical, electrical, or other types of components. In some cases, the touch sensor (or a portion of a touch sensor system) can be configured to detect a touch applied to an outer surface of front cover 106 (e.g., to the display surface of device 100).

[0054] In some cases, a force sensor (or part of a force sensor system) may be positioned within an internal volume above, below, and / or to the side of display 104 (and in some cases, within the device stack). The force sensor (or force sensor system) may be triggered in response to the touch sensor detecting one or more touches on front cover 106 (or one or more locations of one or more touches on front cover 106), and the magnitude of the force associated with each touch, or the magnitude of the force associated with the entire set of touches, may be determined. In some embodiments, the force sensor (or force sensor system) may be used to determine the location of the touch, or the location of the touch combined with the magnitude of the force of the touch. In these latter embodiments, device 100 may not include a separate touch sensor.

[0055] like Figure 1A As shown mainly, the device 100 may include various other components. For example, the front of the device 100 may include one or more front cameras 110 (including one or more image sensors or depth sensors, which in some cases may include one or more PCSELs described herein), speakers 112, microphones, or other components 114 (e.g., audio components, imaging components, and / or sensing components) configured to send signals to the device 100 or receive signals from the device. In some cases, the front camera 110 may be configured to operate as a biometric authentication or facial recognition sensor alone or in combination with other sensors. In some embodiments, a flash or electromagnetic radiation source (e.g., a visible light source or an IR light source) may be positioned near the front camera. In some cases, the front camera 110 may be positioned behind the display 104 and receive electromagnetic radiation (e.g., light) that passes through the display 104. In some cases, the depth sensor may be used to determine the distance to the user or generate a depth map of the user's face, or determine the distance or proximity to an object, or generate a depth map of an object or a FoV including an object. The device 100 may also include various input devices, including mechanical or virtual buttons 116 accessible from the front surface (or display surface) of the device 100 .

[0056] The device 100 may also include buttons or other input devices positioned along the sidewalls 118 and / or on the rear surface of the device 100. For example, a volume button or multi-function button 120 may be positioned along the sidewall 118, and in some cases may extend through a hole in the sidewall 118. The sidewall 118 may include one or more ports 122 that allow air, but not liquid, to flow into and out of the device 100. In some embodiments, one or more sensors may be positioned in or near the ports 122. For example, an ambient pressure sensor, an ambient temperature sensor, an internal / external differential pressure sensor, a gas sensor, a particulate matter concentration sensor, or an air quality sensor may be positioned in or near the port 122.

[0057] In some embodiments, the rear surface of device 100 may include a rear camera 124 that includes one or more image sensors or depth sensors (see Figure 1B ), which in some cases may include one or more of the PCSELs described herein. A flash or electromagnetic radiation source 126 (e.g., a visible light source or an IR light source) may also be positioned on the rear of device 100 (e.g., near a rear-facing camera). In some cases, the rear surface of device 100 may include multiple rear-facing cameras.

[0058] Figure 1C 1 is a simplified block diagram 130 of a LIDAR 132, which may include one or more of the various PCSELs disclosed herein. The LIDAR 132 may be used to detect the distance of an object in the external environment, such as a tree 136a or a building 136b. The LIDAR 132 may use the detected distances to form a depth map or one or more other images of the external environment. The LIDAR 132 may be handheld, mounted to a fixed object, or carried by a moving vehicle or aircraft.

[0059] LIDAR 132 can emit light directionally toward an object. Figure 1C In the particular case shown, the LIDAR 132 may sequentially emit a plurality of light pulses 134a in a first plane, followed by sequentially emitting a second set of light pulses 134b in a second plane. Although only two planes are shown that are swept by the light pulses 134a and 134b, the LIDAR 132 may emit light pulses across more planes. The light pulses may be laser pulses, such as may be emitted from one or more laser diodes within the LIDAR 132. The plane and the direction within the plane of the emitted laser pulses are controlled by a mechanism within the LIDAR 132, such as a steerable optical device, or by sequential emission of laser pulses from a laser diode array in which the laser diodes are aimed in different directions to allow for vertical and horizontal scanning of the external environment.

[0060] The LIDAR 132 may receive reflections 138a-d of the transmitted light pulses, such as by one or more photodetectors that may be in an array. The photodetectors may be implemented in one or more of a variety of technologies, such as resonant cavity photodiodes, single photon avalanche diodes, CMOS photodetectors, or another technology.

[0061] The LIDAR 132 can use the time-of-flight measurement between the emission of a light pulse and the receipt of its reflection to estimate the distance to a portion of an object along the direction of the emitted light pulse. Such directional distance estimates over the entire emitted light pulse can then be combined to detect an object, generate a depth map, or generate other types of information about the external environment of the LIDAR 132.

[0062] Alternatively, the laser diode of the LIDAR 132 may be configured to undergo SMI with reflections of its emitted light. In SMI, reflections of the emitted laser light are received back into the resonant cavity of the laser diode, thereby causing a change in the emitted light (e.g., frequency), wherein this change in light changes a measurable parameter of the laser diode (e.g., forward bias current) or a PD associated with the laser diode.

[0063] Figures 1A to 1C Various examples of electronic devices that utilize emitted light and received reflections to sense the external environment and objects therein are described. However, those skilled in the art will recognize that other types and categories of electronic devices may also utilize emitted light and received reflections for sensing, and the embodiments disclosed herein are not limited to any particular type or category of electronic devices.

[0064] Figure 2A An exploded view of some of the various layers that may be present in or with the PCSEL 200 is shown. As described in the following embodiments, the PCSEL 200 may be part of an SMI sensor, an FMCW sensor, or another electronic device. In the following description, directional statements are relative to Figure 2A . The PCSEL 200 is configured to emit laser light (also referred to as a "primary light emission") 216 vertically upward. The PCSEL 200 is formed with a substrate layer (or just "substrate") 204, which in some embodiments may be an n-type doped (or just "n-type") semiconductor, such as silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), or other III-V semiconductors. The substrate 204 may be formed over a first semiconductor cladding layer 206, which in some embodiments may be a constituent semiconductor of Si, GaAs, InP, or other III-V semiconductors. In embodiments where the substrate 204 is n-type doped, the first semiconductor cladding layer 206 may be n-type doped such that together they form at least a portion of the cathode region of the diode structure.

[0065] PCSEL 200 includes an active region 208 that may include quantum wells and provide laser amplification. Below active region 208 is a photonic crystal layer 210, which in some embodiments includes a planar array having a photonic crystal structure, as described below with respect to Figure 2BThe photonic crystal layer 210 may be formed as a semiconductor material layer, such as Si, GaAs, InP or other III-IV semiconductors. The photonic crystal layer 210 may be formed with gaps. As known to those skilled in the art, the active region 208 may be separated from the photonic crystal layer 210 by a thin electron blocking layer (not shown).

[0066] Below the photonic crystal layer 210 is a second semiconductor cladding layer 212, which is p-type doped to form the anode portion of the diode structure of the PCSEL 200. The semiconductor constituting the second semiconductor cladding layer 212 may be Si, GaAs, InP or other III-V semiconductors.

[0067] exist Figure 2A In the illustrated embodiment, the first electrode 202 is formed on the top side of the substrate 204. The first electrode 202 may be formed around the edge of the substrate 204 to provide an increase in the surface area for the primary light emission 216 of the PCSEL 200. The second electrode 214 is formed on the side of the second semiconductor cladding layer 212 opposite the photonic crystal layer 210. The first electrode 202 and the second electrode 214 may be a metal, such as gold or another conductive material. Although shown as a rectangular configuration, the first electrode 202 and other described components of the PCSEL 200 itself may be formed with another configuration, such as a pattern of cylindrical layers.

[0068] In addition to the primary light emission 216, the PCSEL 200 is also operable to emit light generated in the active region through the photonic crystal layer 210 and the second semiconductor cladding layer 212 as a secondary light emission (not shown) vertically downward in the opposite direction of the primary light emission 216. As described in the following embodiments, when used as a component in an SMI sensor or an FMCW sensor, the primary light emission 216 can be directed to the outside of the sensor, while the secondary light emission is directed to a photodetector.

[0069] Figure 2B A top view of a cross section of a photonic crystal layer 220 is shown. The photonic crystal layer 220 has a three-dimensional rectangular pattern of voids or holes in the semiconductor substrate, as shown by 222a-c in the first row and 224a-c in the second row. Although only three voids are shown in each of the two rows, those skilled in the art will recognize that various embodiments of the photonic crystal layer 220 may have other numbers of rows, with various numbers of voids in each row. The voids 222a-c and 224a-c shown have an approximately trapezoidal shape, although this is not required; in other embodiments, the voids may have a rectangular, triangular, circular or other shape. In some embodiments, the inter-void spacing a may be approximately 0.5 μm, while the width or length of the photonic crystal layer is approximately 400 μm. In some embodiments, the void pattern may be arranged in a pattern other than a rectangle.

[0070] Figure 3 is a cross-sectional view of a first embodiment of a SMI sensor 300. The SMI sensor 300 includes at least a PCSEL portion (or just "PCSEL") and an integrated photodetector portion. The SMI sensor 300 includes a substrate 302 on which components of the PCSEL and the integrated photodetector portion are layered. The substrate 302 can be a semiconductor, such as Si, GaAs, InP, or another III-V semiconductor. The components of the PCSEL of the SMI sensor 300 include a first semiconductor cladding layer 304, an active region 306, a photonic crystal layer 308, and a second semiconductor cladding layer 310. The photodetector component of the SMI sensor 300 includes a first DBR 312 and a second DBR 316 on opposite sides of a photodetector absorption layer 314. The first DBR 312 is connected to the second semiconductor cladding layer 310.

[0071] The first semiconductor cladding layer 304, the active region 306, the photonic crystal layer 308, the second semiconductor cladding layer 310, the first DBR 312, the photodetector absorption layer 314 and the second DBR 316 may be sequentially formed on the substrate 302 by any of various semiconductor manufacturing techniques, such as epitaxial deposition.

[0072] The SMI sensor 300 may have one or more top electrodes 311a-b formed on the primary light emission side of the substrate 302, which is the side of the substrate 302 that emits the primary light emission 320. Figure 3 In the orientation of , the primary light emitting side is the top of substrate 302. Although shown as two parts, the top electrodes 311a-b can be connected, for example for Figure 2A The SMI sensor 300 may also have one or more intermediate electrodes 313a-b, which may be connected, such as connected in a ring around the second semiconductor cladding layer 310. The SMI sensor 300 may also include one or more base electrodes 319 on the side of the second DBR 316 opposite the photodetector absorption layer 314.

[0073] The photodetector absorption layer 314 may be formed with a single or multiple absorption layers (such as formed with InGaAs, GaAs, etc.) or formed with a single or multiple quantum well structures (eg, InGaAs / GaAs, InGaAs / GaAsP, etc.).

[0074] In some embodiments, substrate 302 and first semiconductor cladding layer 304 have n-type doping and form the cathode portion of the PCSEL. In such embodiments, second semiconductor cladding layer 310 is formed with p-type doping and forms the anode portion. In such embodiments, in the integrated photodetector portion of SMI sensor 300, first DBR 312 may be n-type doped, while second DBR 316 has p-type doping. Thus, the integrated photodetector portion also has a diode structure.

[0075] When a higher voltage is applied to the middle electrodes 313a-b relative to the lower voltage applied to the top electrodes 311a-b, charge carriers are injected into the PCSEL and laser emission from the active region 306 may be induced, resulting in a primary light emission 320 passing through the first semiconductor cladding layer 304 and the substrate 302 and emitted from the SMI sensor 300 toward an object 324 in the external environment of the SMI sensor 300. Under these applied voltages, if a lower voltage is additionally applied at the base electrode 319 than at the middle electrodes 313a-b, the photodetector portion is electrically a reverse biased diode and the photodetector absorption layer 314 may operate as a resonant cavity.

[0076] The active region 306 can emit not only the primary light emission 320, but also secondary light emissions that pass through the photonic crystal layer 308 and the second semiconductor cladding layer 310 and are received in the photodetector absorption layer 314. This reception can produce a photocurrent output from the photodetector portion. The photocurrent output or another measurable electrical parameter can be used by the SMI sensor 300 as part of estimating the distance to the object 324. One such measurable electrical parameter can be the junction voltage measured between the intermediate electrodes 313a-b and the base electrode 319.

[0077] The SMI sensor 300 may be configured to use self-mixing interference between a primary light emission 320 and a reflection 322 of the primary light emission 320 received from an object 324. When the received reflection 322 enters the lasing cavity of the active region 306, the frequency or another property of the primary light emission 320 may be different than if no reflection was received. Then, the frequency of the secondary light emission received in the light detecting absorption layer 314 also changes. The change in the secondary light emission may change the photocurrent or another electrical parameter in the reverse biased photodetector portion of the SMI sensor 300, thereby allowing the distance to the object 324 to be estimated.

[0078] Figure 44 is a cross-sectional view of a second embodiment of an SMI sensor 400. The SMI sensor 400 includes at least a PCSEL portion (or just "PCSEL") and an associated photodetector separated from the PCSEL by a space or gap. The SMI sensor 400 includes a substrate 402 on which components of the PCSEL are layered. The substrate 402 can be a semiconductor substrate layer formed of a semiconductor such as Si, GaAs, InP, or another III-V semiconductor. The components of the PCSEL of the SMI sensor 400 include a first semiconductor cladding layer 404, an active region 406, a photonic crystal layer 408, and a second semiconductor cladding layer 410.

[0079] The substrate 402, the first semiconductor cladding layer 404, the active region 406, the photonic crystal layer 408 and the second semiconductor cladding layer 410 may be as described in Figure 3 Similar corresponding components of the SMI sensor 300 are described above, and therefore, for the sake of brevity, those descriptions will not be repeated. The PCSEL portion of the SMI sensor 400 also includes a DBR 412 that is bonded to a side of the second semiconductor cladding layer 410 opposite the photonic crystal layer 408 .

[0080] The first semiconductor cladding layer 404 , the active region 406 , the photonic crystal layer 408 , the second semiconductor cladding layer 410 , and the DBR 412 may be sequentially formed on the substrate 402 by any of various semiconductor manufacturing techniques, such as epitaxial deposition.

[0081] The SMI sensor 400 may have one or more top electrodes 411a-b formed on the primary light emission side of the substrate 402, which is the side of the substrate 402 that emits the primary light emission 420. Figure 4 In the orientation of , the primary light emitting side is the top of substrate 402. Although shown as two parts, the top electrodes 411a-b can be connected, such as for Figure 2A The DBR 412 has one or more base electrodes 413 on the side opposite to the second semiconductor cladding layer 410.

[0082] The photodetector portion of the SMI sensor 400 includes an external photodetector 414 (or just "photodetector") separated from the PCSEL portion. The photodetector 414 includes one or more connector electrodes 417 on a first side facing the DBR 412, wherein the connector electrodes 417 are electrically connected to one or more base electrodes 413 on the DBR 412. The photodetector 414 also includes one or more bottom electrodes 419 on a side of the photodetector 414 opposite to the first side. The PCSEL portion of the SMI sensor 400 and the photodetector portion of the SMI sensor 400 may be formed on separate semiconductor chips and subsequently bonded or linked.

[0083] When the external photodetector 414 is separated from the PCSEL portion of the SMI sensor 400, the external photodetector 414 can be implemented in a variety of photodetector technologies. In one class of embodiments, the external photodetector 414 can be constructed as an active region between a pair of DBRs, such as in Figure 3 In the case of the photodetector portion of the SMI sensor 300 of FIG. 4 , the external photodetector 414 may be implemented with a CMOS photodetector structure. Other technologies for the external photodetector 414 may be used. In order to detect self-mixing interference in the PCSEL portion of the SMI sensor 400, the external photodetector 414 may be selected to be capable of detecting changes in an electromagnetic property (such as frequency or amplitude) of the light it receives.

[0084] The SMI sensor 400 is configured to detect the self-mixing interference of a primary light emission 420 with its reflection 422 from an object 424. In some embodiments, the substrate 402 and the first semiconductor cladding layer 404 have n-type doping, and the DBR 412 has p-type doping to form a diode structure that is forward biased when a higher voltage is applied to the base electrode 413 relative to the lower voltage applied to the top electrodes 411a-b. Under this forward bias, charge carriers are injected into the active region and laser emission may then occur. The DBR 412 may act as a mirror for a lasing cavity.

[0085] As described above, the self-mixing interference of the active region 406 of the primary light emission 420 with the reflection 422 from the object 424 can cause one or more changes in the electromagnetic properties (such as frequency or amplitude) of the generated and emitted laser light. The SMI sensor 400 also emits a secondary light emission 426 having those changes through the second semiconductor cladding layer 410 and the DBR 412 toward the photodetector 414.

[0086] Although in Figure 4412, but the secondary light emission 426 may be emitted from a central location on the DBR 412, which may have a base electrode located on the edge, similar to Figure 2A The photodetector 414 may also have its corresponding connector electrode 417 similarly located on the edge of its surface.

[0087] When the PCSEL portion of the SMI sensor 400 has a forward bias applied between the base electrode 413 and the top electrodes 411a-b, thereby causing lasing, a voltage applied between the connector electrode 417 and the bottom electrode 419 enables the photodetector 414 to detect secondary light emission 426. In embodiments where the photodetector 414 is constructed as an active region between a pair of DBRs of alternating doping types, a reverse bias is applied so that the photodetector 414 can operate as a resonant cavity photodetector.

[0088] In additional and / or alternative embodiments, SMI sensor 300 and SMI sensor 400 may further include a second DBR positioned on the light emitting side of the respective substrates 302 and 402. The second DBR may include fewer alternating layers than DBR 412 and may provide a greater primary emission side surface reflectivity for the PCSEL structure. Such a second DBR may allow the feedback coefficient to be adjusted to improve the signal-to-noise ratio.

[0089] Despite Figure 3 to Figure 4 It is not explicitly shown, but those skilled in the art will recognize that both SMI sensor 300 and SMI sensor 400 may include additional electronic circuits, such as one or more: voltage or current sources, ground connections, amplifiers, transistors, bypass diodes, or other components. Other types of components that may be included are on-chip lenses, protective layers, etc.

[0090] Figure 5A A cross-sectional view of an embodiment of an FMCW sensor 500 that utilizes FMCW measurements to detect information (distance, motion, etc.) about an object 524 in an external environment is shown. The FMCW sensor 500 emits a primary light emission 520 toward the object and emits secondary light emissions 526a-b toward a light combining unit (or "beam combiner") 528. Reflections 522a-b of the primary light emission 520 from the object 524 are combined with the secondary light emissions 526a-b to generate a net frequency modulated light. In the case where the FMCW sensor 500 changes the frequency of the primary light emission 520 in a known manner, information about the distance and motion to the object 524 can be estimated from the net frequency modulated light. The PCSEL structure can emit laser light with a narrower laser line width than other types of laser diodes (such as VCSELs or EELs). This can allow the FMCW sensor 500 to sense the object 524 at a longer distance.

[0091] The FMCW sensor 500 includes a semiconductor current distribution layer 502 having a light emitting side through which a primary light emission 520 is emitted toward an object 524. In the configuration shown in FIG. 5 , the light emitting side is on top of the semiconductor current distribution layer 502. In the FMCW sensor 500, the semiconductor current distribution layer 502 forms the top layer of the PCSEL structure. Moving sequentially away from the semiconductor current distribution layer 502, the PCSEL includes as components: a first semiconductor cladding layer 504 bonded to a side of the semiconductor current distribution layer 502 opposite to the light emitting side, an active region 506, a photonic crystal layer 508, and a second semiconductor cladding layer 510. These components of the PCSEL may be as described above with respect to Figures 2A to 4 These components are formed sequentially so that the active region is located between the first semiconductor cladding layer 504 and the photonic crystal layer 508 , and the photonic crystal layer 508 is located between the active region 506 and the second semiconductor cladding layer 510 .

[0092] The FMCW sensor 500 also includes a DBR 512 on a side of the second semiconductor cladding layer 510 opposite the photonic crystal layer 508. The FMCW sensor 500 may also include a tunnel junction 514, as described below with respect to Figure 5B As described, the tunnel junction is formed on the side of the DBR 512 opposite to the second semiconductor cladding layer 510. In the embodiment shown in Figure 5, the FMCW includes a semiconducting substrate layer 516 on the side of the tunnel junction opposite to the DBR 512. The semiconductor substrate layer 516 can be Si, GaAs, InP or another III-V semiconductor.

[0093] Semiconductor current distribution layer 502, first semiconductor cladding layer 504, active region 506, photonic crystal layer 508, second semiconductor cladding layer 510, DBR 512, tunnel junction 514 and semiconducting base layer 516 may be formed on a single semiconductor wafer, for example, by epitaxial or vapor deposition, ion implantation or other techniques.

[0094] In some embodiments of the FMCW sensor 500, the semiconductor current distribution layer 502 and the first semiconductor cladding layer 504 are n-type doped. In these embodiments, the second semiconductor cladding layer 510 is p-type doped. Figure 5B A cross-section 530 of a tunnel junction 514 of these embodiments is shown. The tunnel junction 514 includes a first tunnel junction layer 532 that is bonded to the side of the DBR 512 opposite the second semiconductor cladding layer 510. The first tunnel junction layer 532 has a p-type doping, which may be heavy (dopant concentration greater than 5×10 18 cm -3) p-type doped (p++). The second tunnel junction layer 534 has n-type doping, which may be heavily n-type doped (n++). In embodiments including the tunnel junction 514, the semiconducting base layer 516 has n-type doping.

[0095] In an alternative embodiment, tunnel junction 514 may not be included, in which case semiconducting base layer 516 has a p-type doping.

[0096] One or more electrodes 511a-b are formed on the light emitting side of the semiconductor current distribution layer 502. The electrodes 511a-b may be a single metal ring (rectangular, circular, etc.) around the edge of the light emitting side of the semiconductor current distribution layer 502, similar to Figure 2A 514. The first electrode 202 shown in FIG. 514 is a semiconductor substrate layer 516. One or more other electrodes 513 may be formed on a side of the semiconductor substrate layer 516 opposite the tunnel junction 514. When a higher voltage is applied at the electrode 513 than the voltage applied at the electrodes 511a-b, a forward bias occurs in the PCSEL structure of the FMCW sensor 500, so that lasing may occur, resulting in a primary light emission 520 emitted toward an object 524. In addition, secondary light emissions 526a-b may also be emitted through the semiconductive substrate layer 516. The semiconductive substrate layer 516 may include one or more on-chip lenses 518a-b that direct the secondary light emissions 526a-b toward a beam combiner 528. The beam combiner 528 may be separated from the semiconductor substrate layer 516 by a space or gap.

[0097] Primary light emission 520 may impinge on object 524 and produce reflections 522a-b. Reflections 522 may then be received in beam combiner 528 instead of in the PCSEL portion of FMCW sensor 500. Secondary light emissions 526a-b may be used as local oscillators for FM sensing.

[0098] Figure 5C A configuration 540 of components of a beam combiner 528 is shown. Secondary light emissions 526a-b and reflections 522a-b of primary light emissions 520 from an object 524 are received in a particular beam combiner 529 to produce a combined light beam that is input into a waveguide 546. Waveguide 546 may be a fiber optic waveguide. A beam splitter 548 then splits the combined light beam equally and sends the two separated light beams to a pair of balanced photodetectors 550a and 550b, which may be operated as diodes powered by a high voltage 551 and a ground voltage 553. Amplifier 552 may be a transimpedance amplifier for amplifying the detected FMCW signal. The output of amplifier 552 is received by a processing element 554 within the FMCW sensor 500 or in an electronic device containing the FMCW sensor 500.

[0099] Figure 5D A cross-sectional view of another embodiment 560 of the beam combiner 528 is shown. Embodiment 560 includes two photosensors 562a and 562b. The two photosensors 562a and 562b can be both or separately implemented as resonant cavity photodiodes (RCPDs) or CMOS photodetectors or another photodetector technology. The two photosensors 562a and 562b are powered by top electrodes 565a and 565b and bottom electrodes 567a and 567b, respectively.

[0100] The two photosensors 562a and 562b are each connected to the corresponding metasurfaces 564a and 564b. The metasurface 564a is used to combine the incident reflection 522 and the secondary light emission 526a, which may have different incident angles on the metasurface 546a, into a combined light beam received by the photosensor 562a. The metasurface 564b is used to combine the incident reflection 522 and the secondary light emission 526b, which may have different incident angles on the metasurface 546b, into a combined light beam received by the photosensor 562b.

[0101] An amplifier 568, such as a transimpedance amplifier, may take as differential inputs the photocurrents or another pair of electrical outputs generated from the two photosensors 562a and 562b at the top electrodes 565a and 565b. The output of the amplifier 568 is received at a processor or processing unit 570, which may be included in the embodiment 560 of the beam combiner 528, or in a component of an electronic device that includes the FMCW sensor 500.

[0102] Those skilled in the art will recognize that the individually described SMI sensor 300, SMI sensor 400, and FMCW sensor 500 may be part of a respective array of such sensors. Figure 3 The PCSEL structures of the SMI sensor 300, SMI sensor 400, and FMCW sensor 500 shown in the corresponding cross-sections of FIG. 5 may be formed on a single chip as part of an array of such PCSEL structures. Figure 3 The RCPD structure of the PD portion of the SMI sensor 300 may also be formed in a Figure 3 Multiple copies of the PD structure of SMI sensor 400 can be formed as separate individual chips and arranged toward the PCSEL array, as described with respect to Figure 4 Similarly, multiple copies of the PD structure or beam combiner of the FMCW sensor 500 may be formed as separate single chips and arranged toward a PCSEL array, as described with respect to FIG. 5 .

[0103] Although not explicitly shown in FIG5 , one skilled in the art will recognize that the FMCW sensor 500 may include additional electronic circuitry, such as one or more of: a voltage source or current source, a ground connection, an amplifier, a transistor, a bypass diode, or other components. Other types of components that may be included are on-chip lenses, protective layers, etc.

[0104] Figure 6 A PCSEL-based SMI or FMCW sensor (such as reference FIG. 1A to FIG. 5D 600) is an example electrical block diagram of an electronic device 600 having any of the SMI sensors described in any of the PCSEL-based sensors. The electronic device 600 may be an image sensor, a depth sensor, or another type of sensor. The electronic device 600 may take the form of, for example, a handheld or portable device (e.g., a smart phone, a tablet computer, or an electronic watch), a navigation system for a vehicle, etc. The electronic device 600 may include an optional display 602 (e.g., a light-emitting display), a processor 604, a power supply 606, a memory 608 or a storage device, a sensor system 610, and an optional input / output (I / O) mechanism 612 (e.g., an input / output device and / or an input / output port). The processor 604 may control some or all operations of the electronic device 600. The processor 604 may communicate directly or indirectly with substantially all components of the electronic device 600. For example, a system bus or other communication mechanism 614 may provide communication between the processor 604, the power supply 606, the memory 608, the sensor system 610, and / or the input / output mechanism 612.

[0105] Processor 604 may be implemented as any electronic device capable of processing, receiving, or sending data or instructions. For example, processor 604 may be a microprocessor, a central processing unit (CPU), an application specific integrated circuit (ASIC), a digital signal processor (DSP), a controller, or any combination of such devices. As used herein, the term "processor" is intended to encompass a single processor or processing unit, multiple processors, multiple processing units, or one or more other appropriately configured computing elements.

[0106] In some embodiments, components of the electronic device 600 may be controlled by multiple processors. For example, selected components of the electronic device 600 may be controlled by a first processor, and other components of the electronic device 600 may be controlled by a second processor, wherein the first processor and the second processor may or may not communicate with each other.

[0107] The power supply 606 may be implemented using any device capable of providing energy to the electronic device 600. For example, the power supply 606 may include one or more disposable or rechargeable batteries. Additionally or alternatively, the power supply 606 may include a power connector or a power cord that connects the electronic device 600 to another power source, such as a wall outlet.

[0108] The memory 608 can store electronic data that can be used by the electronic device 600. For example, the memory 608 can store electronic data or content, such as, for example, audio and video files, documents and applications, device settings and user preferences, timing signals, control signals, data structures or databases, image data, maps, or focus settings. The memory 608 can be configured as any type of memory. By way of example only, the memory 608 can be implemented as a random access memory, a read-only memory, a flash memory, a removable memory, other types of storage elements, or a combination of such devices.

[0109] The electronic device 600 may also include one or more sensors defining a sensor system 610, such as FIG. 1A to FIG. 5D Any of the described PCSEL-based sensors, as well as other types of sensors. The sensors may be positioned substantially anywhere on the electronic device 600. The sensors may be configured to sense substantially any type of characteristic, such as, but not limited to, touch, force, pressure, electromagnetic radiation (e.g., light), heat, movement, relative motion, biometric data, distance, and the like. For example, the sensor system 610 may include a touch sensor, a force sensor, a thermal sensor, a position sensor, a light or optical sensor, an accelerometer, a pressure sensor (e.g., a pressure transducer), a gyroscope, a magnetometer, a health monitoring sensor, an image sensor, a SPAD-based photon detector, and the like. In addition, one or more sensors may utilize any appropriate sensing technology, including, but not limited to, capacitive, ultrasonic, resistive, optical, ultrasonic, piezoelectric, and thermal sensing technologies.

[0110] I / O mechanisms 612 can send and / or receive data from a user or another electronic device. I / O devices may include a display, a touch-sensing input surface such as a trackpad, one or more buttons (e.g., a graphical user interface "home" button or one of the buttons described herein), one or more cameras (including one or more 2D or 3D image sensors, such as those described above with respect to FIG. 1A to FIG. 5DThe I / O mechanism 612 may include any of the PCSEL-based sensors, and / or one or more SPAD-based photon detectors), one or more microphones or speakers, one or more ports such as a microphone port, and / or a keyboard. In addition or alternatively, the I / O device or port may send electrical signals via a communication network such as a wireless and / or wired network connection. Examples of wireless and wired network connections include, but are not limited to, cellular networks, Wi-Fi, Bluetooth, IR, and Ethernet connections. The I / O mechanism 612 may also provide feedback to the user (e.g., tactile output).

[0111] For the purpose of illustration, the foregoing description uses specific nomenclature to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that specific details are not required in order to practice the embodiments. Therefore, for the purpose of illustration and description, the foregoing description of the specific embodiments described herein is presented. They are not intended to be exhaustive or to limit the embodiments to the disclosed precise forms. It will be apparent to those of ordinary skill in the art that, in view of the above teachings, many modifications and variations are feasible.

Claims

1. A self-mixing interferometry (SMI) sensor, the SMI sensor comprising: substrate; A photonic crystal surface emitting laser diode, the photonic crystal surface emitting laser diode being disposed on the substrate and configured to perform a single light emission through the substrate, the photonic crystal surface emitting laser diode comprising: Photonic crystal layer; an active region, the active region being disposed between the photonic crystal layer and the substrate, the active region having a primary emission side, through which the primary light emission occurs; a first semiconductor cladding layer, the first semiconductor cladding layer being disposed on the primary emission side of the active region and between the active region and the substrate; and a second semiconductor cladding layer, the second semiconductor cladding layer being disposed on a secondary light emission side of the active region, the secondary light emission side being opposite to the primary emission side, the photonic crystal layer being disposed between the second semiconductor cladding layer and the active region; a distributed Bragg reflector DBR, the DBR being disposed on the second semiconductor cladding layer, so that the second semiconductor cladding layer is disposed between the DBR and the photonic crystal layer; and a photodetector positioned proximate to the DBR and configured to receive secondary light emission emitted from the photonic crystal surface emitting laser diode through the second semiconductor cladding layer and the DBR, the photodetector configured to produce a measurable electrical parameter related to self-mixing of light within the photonic crystal surface emitting laser diode.

2. The SMI sensor of claim 1, wherein the photonic crystal layer defines a patterned photonic crystal structure.

3. The SMI sensor according to claim 1, wherein: The DBR is a first DBR; and The photodetector comprises: a photodetector absorbing layer adjacent to the first DBR and opposite to the second semiconductor cladding layer; and A second DBR is adjacent to the photodetector absorber layer and opposite to the first DBR.

4. The SMI sensor according to claim 3, wherein: The photonic crystal surface emitting laser diode and the photodetector include epitaxial layers on the substrate; and The measurable electrical parameter related to the self-mixing is the photocurrent of the photodetector.

5. The SMI sensor according to claim 3, wherein: The substrate includes a semiconductor doped to an n-type; and The semiconductor of the substrate includes one of gallium arsenide (GaAs) or indium phosphide (InP).

6. The SMI sensor according to claim 3, wherein: The first DBR has n-type doping and the second DBR has p-type doping; the photodetector absorber layer is bonded to the first DBR; and At least during the secondary light emission of the photonic crystal surface emitting laser diode, the first DBR is biased with a first voltage higher than a second voltage applied to the second DBR.

7. The SMI sensor according to claim 1, wherein: The photodetector is spaced apart from the DBR; and The photodetector is electrically connected to the DBR through a metal link between at least a first electrode on the DBR and at least a second electrode on the photodetector.

8. The SMI sensor according to claim 7, wherein: The substrate includes a semiconductor doped to an n-type; The semiconductor includes one of gallium arsenide (GaAs), indium phosphide (InP), indium gallium arsenide (InGaAs), aluminum gallium arsenide (AlGaAs) or indium gallium arsenide phosphide (InGaAsP); The photonic crystal surface emitting laser diode and the DBR include epitaxial layers on the substrate; and The measurable electrical parameter related to the self-mixing is the photocurrent of the photodetector.

9. The SMI sensor according to claim 1, further comprising: An additional DBR is adjacent to the substrate and opposite the first semiconductor cladding layer, the additional DBR having fewer alternating layers than the DBR.

10. A frequency modulated continuous wave (FMCW) sensor, the FMCW sensor comprising: Semiconductor current distribution layer; A photonic crystal surface emitting laser diode, wherein the photonic crystal surface emitting laser diode is disposed on the semiconductor current distribution layer and is configured to perform a single light emission through the semiconductor current distribution layer, and the photonic crystal surface emitting laser diode comprises: Photonic crystal layer; an active region, the active region being disposed between the photonic crystal layer and the semiconductor current distribution layer, the active region having a primary emission side, through which the primary light emission occurs; a first semiconductor cladding layer disposed on the primary emission side of the active region and between the active region and the semiconductor current distribution layer; and a second semiconductor cladding layer, the second semiconductor cladding layer being arranged on the secondary light emission side of the active region, the secondary light emission side being opposite to the primary emission side, the photonic crystal layer being arranged between the second semiconductor cladding layer and the active region; a distributed Bragg reflector DBR, the DBR being arranged on the second semiconductor cladding layer, so that the second semiconductor cladding layer is arranged between the DBR and the photonic crystal layer; A semiconductor base layer, the semiconductor base layer is adjacent to the DBR and opposite to the second semiconductor cladding layer; a beam combiner positioned across a gap from the semiconductor substrate layer of the photonic crystal surface emitting laser diode and configured to produce a FMCW optical output by combining a reflection of the primary light emission emitted from the primary emission side of the active region and a secondary light emission emitted from the secondary light emission side of the active region, the secondary light emission being emitted through the semiconductor substrate layer; and An optoelectronic circuit is configured to receive the FMCW optical output and to generate a measurable electrical parameter related to modulation of the FMCW optical output.

11. The FMCW sensor according to claim 10, wherein: The semiconductor current distribution layer has n-type doping; The first semiconductor cladding layer has n-type doping; The second semiconductor cladding layer has p-type doping; The DBR has p-type doping; and The semiconductor base layer has n-type doping and is one of gallium arsenide (GaAs), indium phosphide (InP), indium gallium arsenide (InGaAs), aluminum gallium arsenide (AlGaAs) or indium gallium arsenide phosphide (InGaAsP).

12. The FMCW sensor according to claim 11, further comprising a tunnel junction, wherein the tunnel junction is disposed between the DBR and the semiconductor substrate layer; wherein the tunnel junction comprises: a heavily p-type doped layer, the heavily p-type doped layer being adjacent to the DBR; and A heavily n-type doped layer is adjacent to the p-type doped layer and opposite to the DBR.

13. The FMCW sensor of claim 11, wherein the photonic crystal surface emitting laser diode further comprises at least one on-chip lens positioned on the semiconductor substrate layer and configured to direct the secondary light emission to the beam combiner.

14. The FMCW sensor according to claim 11, wherein: The beam combiner comprises: a first metasurface configured to combine the reflection of the primary light emission with a secondary light emission and produce a first combined light output; and a second metasurface configured to combine the reflection of the primary light emission with a secondary light emission and produce a second combined light output; and The optoelectronic circuit comprises: a first photodetector positioned to receive the first combined light output; and a second photodetector positioned to receive the second combined light output; and An amplifier is configured to receive both the electrical output of the first photodetector and the electrical output of the second photodetector.

15. The FMCW sensor of claim 14, wherein the first photodetector and the second photodetector are balanced photodetectors. 16 . The FMCW sensor of claim 14 , wherein the electrical output of the first photodetector and the electrical output of the second photodetector are photocurrents.

17. An electronic device, comprising: an array of photonic crystal surface emitting laser diodes, each photonic crystal surface emitting laser diode operable to emit a single light emission from the photonic crystal surface emitting laser diode through a light emitting surface of the electronic device toward one or more objects external to the electronic device; a photodetector array configured to receive at least secondary light emissions emitted from the photonic crystal surface emitting laser diodes in the photonic crystal surface emitting laser diode array toward the photodetector array; and an electronic circuit configured to receive a measurable output signal from a photodetector in the photodetector array; wherein: Each photonic crystal surface emitting laser diode in the photonic crystal surface emitting laser diode array comprises: an n-doped current distribution layer, the n-doped current distribution layer being close to the light emitting surface of the electronic device, the primary light emission being emitted from the electronic device through the light emitting surface; an n-type cladding layer adjacent to the n-doped current distribution layer and opposite the light emitting surface of the electronic device; an active region, the active region being adjacent to the n-type cladding layer and opposite to the semiconductor base layer; a photonic crystal layer, the photonic crystal layer being adjacent to the active region and opposite to the n-type cladding layer; a p-type cladding layer adjacent to the photonic crystal layer and opposite to the active region; and A p-type distributed Bragg reflector (DBR) layer is adjacent to the p-type cladding layer and opposite to the photonic crystal layer.

18. The electronic device according to claim 17, wherein: The photonic crystal surface emitting laser diodes in the photonic crystal surface emitting laser diode array are individually addressable by the electronic circuit; and The electronic circuitry is operable to generate a depth map of the one or more objects external to the electronic device using the measurable output signals from the photodetectors in the photodetector array.

19. The electronic device according to claim 18, wherein: The photodetectors in the photodetector array include a photodetector absorbing layer; The photodetectors in the photodetector array generate output signals related to self-mixing interference of the secondary light emissions with reflections of the primary light emissions from the one or more objects external to the electronic device; and The output signal associated with the self-mixing interference is included in the measurable output signal used by the electronic device to generate the depth map.

20. The electronic device according to claim 18, wherein: The photodetectors in the photodetector array include a pair of separated and balanced semiconductor photodetectors having corresponding metasurfaces; The metasurface is configured to combine the secondary light emission with reflections of the primary light emission from the one or more objects external to the electronic device; and The pair of separated and balanced semiconductor photodetectors produce respective output photocurrents that are related to frequency modulation between the combined primary and secondary light emissions.

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