Optical sensor chip

Abstract

The LIDAR chip includes a common waveguide that guides the output LIDAR signal to a facet through which the output LIDAR signal is emitted from the chip. The chip also includes a control branch that removes a portion of the output LIDAR signal from the common waveguide. The control branch includes a control light sensor that receives an optical signal that includes light from the removed portion of the output LIDAR signal. The chip also includes a data branch that removes a second portion of the output LIDAR signal from the common waveguide. The data branch includes an optical combining component that combines a reference optical signal that includes light from the second portion of the output LIDAR signal with a comparison optical signal that includes light reflected from an object located outside the chip.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. patent application serial number 15 / 977,957, filed on May 11, 2018, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to optical devices. In particular, the present invention relates to LIDAR chips. Background Art

[0004] There is an increasing commercial demand for 3D sensing systems that can be economically deployed in applications such as ADAS (Advanced Driver Assistance Systems) and AR (Augmented Reality). LIDAR (Light Detection and Ranging) sensors are used to construct a 3D image of a target scene by illuminating the scene with lasers and measuring the returning signals.

[0005] Frequency modulated continuous wave (FMCW) is an example of a coherent detection method that can be used for LIDAR applications. FMCW technology is able to determine both the distance and speed of an object with a single measurement. In addition, FMCW technology has reduced sensitivity to ambient light and light from other LIDAR systems.

[0006] Integrated FMCW LIDAR chips are not yet available. Furthermore, efforts to create chips that have a portion of the LIDAR chip assembly have been limited in the amount of optical power they can transmit without signal clipping. This signal clipping limits the amount of transmitted laser power to reflective objects. This limitation on the amount of transmitted laser power limits the overall sensitivity of the device. For these reasons, there is a need for a platform that can integrate a LIDAR chip while also providing the optical power required to achieve the desired sensitivity level. Summary of the invention

[0007] The LIDAR chip includes one or more ridge waveguides having a ridge of a light-transmitting medium extending away from a slab region of the light-transmitting medium. The ridge has a width greater than 1 μm and less than 4 μm, and a height greater than 1 μm and less than 4 μm. The slab region has a thickness greater than 0.0 μm and less than 3 μm. In some examples, the chip is a silicon-on-insulator chip.

[0008] Another embodiment of the LIDAR chip includes a common waveguide that guides the outgoing LIDAR signal to a facet through which the outgoing LIDAR signal is emitted from the chip. The chip also includes a control branch that removes a portion of the outgoing LIDAR signal from the common waveguide. The control branch includes a control light sensor that receives an optical signal that includes light from the removed portion of the outgoing LIDAR signal. The chip also includes a data branch that removes a second portion of the outgoing LIDAR signal from the common waveguide. The data branch includes an optical combining component that combines a reference optical signal that includes light from the second portion of the outgoing LIDAR signal with a comparison optical signal that includes light reflected from an object located outside the chip.

[0009] Another embodiment of the chip includes a common waveguide terminating at a facet through which the outgoing LIDAR signal exits the chip. The common waveguide is also configured to receive a LIDAR input light signal through the facet. The LIDAR input light signal includes light from the outgoing LIDAR signal. The chip also includes a data branch including a light sensor configured to receive a light signal including light from the LIDAR input light signal.

[0010] Another embodiment of the chip includes a common waveguide terminating at a facet through which at least a portion of the outgoing LIDAR signal exits the LIDAR chip. The chip also includes an optical attenuator configured to attenuate the strength of the outgoing LIDAR signal on the common waveguide.

[0011] Another embodiment of the chip includes a waveguide that receives a comparison optical signal that includes light from a LIDAR input optical signal. The LIDAR input optical signal includes light reflected by an object located outside the chip. The chip also includes an optical attenuator that is configured to attenuate the intensity of the comparison optical signal on the waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a top view of the LIDAR chip.

[0013] Figure 2 is based on Figure 1 A cross section of a LIDAR chip constructed from a silicon-on-insulator wafer.

[0014] Figure 3 Diagram showing use with off-chip scanning mechanism Figure 1 LIDAR chip.

[0015] Figure 4 The invention is shown in conjunction with another embodiment of an off-chip scanning mechanism. Figure 1 LIDAR chip.

[0016] Figure 5 Has an integrated scanning mechanism Figure 1 A cross section of a LIDAR chip. DETAILED DESCRIPTION

[0017] A LIDAR chip is disclosed that integrates all-optical LIDAR functionality onto a single optical chip. The chip also provides optical components for monitoring and controlling the optical functions of the chip. For example, the chip includes optical components for controlling the frequency and intensity of outgoing LIDAR signals transmitted from the chip. The chip also includes optical components for controlling the intensity of LIDAR input optical signals received by the chip after being reflected by an off-chip object.

[0018] The chip is suitable for structures on various platforms, such as a silicon-on-insulator (SOI) platform. The chip can include multiple waveguides; however, in order to make these chip structures suitable for LIDAR applications, the waveguide size is increased to a size higher than that of standard silicon photonic LIDAR approaches. The LIDAR chip transmits an output optical signal, which is reflected by an object located outside the chip. The LIDAR chip receives a portion of the reflected optical signal. As a result of this mechanism, the power of the reflected optical signal that is actually available to the LIDAR chip for processing may be undesirably low.

[0019] The waveguide dimensions typically used by LIDAR chips constructed from SOI-type platforms are often a source of optical power and phase losses, making these chips difficult or even impossible to apply to LIDAR applications. However, the inventors have discovered that increasing the waveguide dimensions while maintaining a single-mode configuration allows these LIDAR chips to be successfully applied to LIDAR applications. For example, the chip may include ridge waveguides, each ridge waveguide comprising a ridge of an optical transmission medium (such as silicon) extending from a slab region of the optical transmission medium. Constructing the ridge waveguides so that the ridges have a width greater than 1 μm and less than 4 μm, a height greater than 1 μm and less than 4 μm, and extend away from a slab region having a thickness greater than 0.0 μm and less than 3 μm allows the chip to be successfully used in LIDAR applications.

[0020] Figure 11 is a top view of a LIDAR chip including a laser cavity. The laser cavity includes a light source 10, which may include or consist of a gain medium (not shown) for the laser. The chip also includes a cavity waveguide 12 that receives an optical signal from the light source 10. The light source can be positioned in a groove 13 so that a facet of the light source is optically aligned with a facet of the cavity waveguide 12 to allow the light source and the cavity waveguide 12 to exchange optical signals. The cavity waveguide 12 transmits the optical signal to a partial return device 14. The illustrated partial return device 14 is a grating, such as a Bragg grating. However, other partial return devices 14 may be used; for example, a mirror may be used in combination with an echelon grating and an arrayed waveguide grating.

[0021] The partial return device 14 returns the return portion of the optical signal to the cavity waveguide 12 as a return signal. For example, the cavity waveguide 12 returns the return signal to the light source 10, so that the return portion of the optical signal propagates through the gain medium. The light source 10 is configured so that at least a portion of the return signal is added to the optical signal received at the cavity waveguide 12. For example, the light source 10 may include a highly, completely or partially reflective device 15 that reflects the return signal received from the gain medium back into the gain medium. As a result, the light may resonate between the partial return device 14 and the reflective device 15 to form a distributed Bragg reflector (DBR) laser cavity. The DBR laser cavity has an inherently narrow linewidth and a longer coherence length than a DFB laser, and the performance is correspondingly improved when the object reflecting the LIDAR output signal from the chip is located farther away from the chip.

[0022] The partial return device 14 transfers a portion of the optical signal received from the cavity waveguide 12 to a common waveguide 16 included on the chip. The portion of the optical signal received by the common waveguide 16 from the partial return device 14 is used as the output of the laser cavity. The output of the laser cavity is used as the outgoing LIDAR signal on the common waveguide 16. The common waveguide 16 terminates at the facet 18 and transmits the outgoing LIDAR signal to the facet 18. The facet 18 can be positioned so that the outgoing LIDAR signal propagating through the facet 18 is emitted out of the chip and is used as the LIDAR output signal. For example, the facet 18 can be positioned at the edge of the chip so that the outgoing LIDAR signal propagating through the facet 18 is emitted out of the chip and is used as the LIDAR output signal.

[0023] The LIDAR output signal propagates away from the chip and is reflected by an object in the LIDAR signal path. The reflected signal propagates away from the object. At least a portion of the reflected signal returns to the facet 18 of the common waveguide 16. Therefore, a portion of the reflected signal can enter the common waveguide 16 through the facet 18 and serve as the LIDAR input signal guided by the common waveguide 16.

[0024] The common waveguide 16 may include a tapered portion before the facet 18. For example, the common waveguide 16 may include a taper 20 that terminates at the facet 18. The taper 20 may relax the alignment tolerances required to efficiently couple the common waveguide 16 to the LIDAR input light and the outgoing LIDAR signal. Thus, the taper 20 may increase the percentage of LIDAR input signals that are successfully returned to the chip for processing. In some examples, the taper 20 is configured such that the facet 18 has an area that is greater than two, five, or ten times the cross-sectional area of ​​the straight portion of the common waveguide 16. Although Figure 1 The cone 20 is shown as a horizontal cone, but the cone 20 can be a horizontal and / or vertical cone. The horizontal and / or vertical cone can be linear and / or curved. In some examples, the cone 20 is an adiabatic cone.

[0025] The chip includes a data branch 24 in which an optical signal processed for LIDAR data is generated. The data branch includes an optical coupler 26 that moves a portion of the optical signal from the common waveguide 16 into the data branch. For example, the optical coupler 26 couples a portion of the outgoing LIDAR signal from the common waveguide 16 onto a reference waveguide 27 as a reference signal. The reference waveguide 27 transmits the reference signal to an optical combining assembly 28.

[0026] The optical coupler 26 also couples a portion of the LIDAR input signal from the common waveguide 16 to the comparison waveguide 30 as a comparison signal. The comparison signal includes at least a portion of the light from the LIDAR input signal. The comparison signal may exclude light from the reference light signal. The comparison waveguide 30 transmits the comparison signal to the optical combining assembly 28.

[0027] The illustrated optical coupler 26 is the result of positioning the common waveguide 16 sufficiently close to the reference waveguide 27 and the comparison waveguide 30 so that light from the common waveguide 16 is coupled into the reference waveguide 27 and the comparison waveguide 30; however, other signal tapping components may be used to move a portion of the optical signal from the common waveguide 16 to the reference waveguide 27 and the comparison waveguide 30. Examples of suitable signal tapping components include, but are not limited to, y-junctions, multimode interference couplers (MMIs), and integrated optical circulators.

[0028] The light combining component 28 combines the comparison signal and the reference signal into a composite signal. The reference signal includes light from the outgoing LIDAR signal. For example, the reference signal can be used as a sample of the outgoing LIDAR signal. The reference signal can exclude light from the LIDAR output signal and the LIDAR input signal. In contrast, the comparison signal light includes light from the LIDAR input signal. For example, the comparison signal can be used as a sample of the LIDAR input signal. Therefore, the comparison signal has been reflected by an object outside the chip, while the LIDAR output signal has not yet been reflected. When the chip and the reflective object move relative to each other, the comparison signal and the reference signal have different frequencies due to the Doppler effect. As a result, a jump occurs between the comparison signal and the reference signal.

[0029] The light combining assembly 28 also splits the resulting composite sample signal onto a first detector waveguide 36 and a second detector waveguide 38. The first detector waveguide 36 transmits a first portion of the composite sample signal to a first photosensor 40, which converts the first portion of the composite sample signal into a first electrical signal. The second detector waveguide 38 transmits a second portion of the composite sample signal to a second photosensor 42, which converts the second portion of the composite sample signal into a second electrical signal. Examples of suitable photosensors include germanium photodiodes (PDs) and avalanche photodiodes (APDs).

[0030] The optical combination assembly 28, the first light sensor 40, and the second light sensor 42 can be connected as a balanced photodetector that outputs an electrical data signal. For example, the optical combination assembly 28, the first light sensor 40, and the second light sensor 42 can be connected so that the DC components of the signal photocurrent cancel each other, thereby improving the detection sensitivity. A suitable method of connecting the first light sensor 40 and the second light sensor 42 as a balanced photodetector includes connecting the first light sensor 40 and the second light sensor 42 in series. In one example, both the first light sensor 40 and the second light sensor 42 are avalanche photodiodes connected in series. Balanced photodetection is desirable for the detection of small signal fluctuations.

[0031] An example of a suitable optical combining component 28 is a multi-mode interference (MMI) device, such as a 2x2 MMI device. Other suitable optical combining components 28 include, but are not limited to, adiabatic splitters and directional couplers. In some examples, the functions of the illustrated optical combining component 28 are performed by more than one optical component or a combination of optical components.

[0032] A single optical sensor can replace the first optical sensor 40 and the second optical sensor 42, and can output a data signal. When a single optical sensor replaces the first optical sensor 40 and the second optical sensor 42, the optical combination assembly 28 does not need to include a light splitting function. As a result, the illustrated optical combination assembly 28 can be a 2×1 optical combination assembly instead of the illustrated 2×1 optical combination assembly. For example, the illustrated optical combination assembly can be a 2×1 MMI device. In these examples, the chip includes a single detector waveguide that transmits the composite sample signal to the optical sensor.

[0033] The data branch includes a data optical attenuator 44 positioned along the comparison waveguide 30, such that the data optical attenuator 44 can be operated to attenuate the comparison signal on the comparison waveguide 30. The chip also includes an output optical attenuator 46 positioned along the common waveguide 16, such that the output optical attenuator 46 can be operated to attenuate the outgoing LIDAR signal on the common waveguide 16. Suitable attenuators of the data optical attenuator 44 and / or the output optical attenuator 46 are configured to attenuate the intensity of the optical signal. Examples of suitable attenuators configured to attenuate the intensity of the optical signal include carrier injection-based PIN diodes, electro-absorption modulators, and Mach-Zehnder (MZ) modulators.

[0034] The chip also includes a sampling directional coupler 50, which couples a portion of the comparison signal from the comparison waveguide 30 to a sampling waveguide 52. The coupled portion of the comparison signal is used as a sampling signal. The sampling waveguide 52 transmits the sampling signal to a sampling light sensor 54. Figure 1 Sampling directional coupler 50 is shown which moves a portion of the comparison signal to sampling waveguide 52, but other signal tapping components may be used to move a portion of the comparison signal from comparison waveguide 30 to sampling waveguide 52. Examples of suitable signal tapping components include, but are not limited to, y-junctions and MMIs.

[0035] The chip includes a control branch 55 for controlling the operation of the laser cavity. The control branch includes a directional coupler 56 that moves a portion of the outgoing LIDAR signal from the common waveguide 16 to a control waveguide 57. The coupled portion of the outgoing LIDAR signal serves as a tap signal. Figure 1 A directional coupler 56 is shown that moves a portion of the outgoing LIDAR signal to the control waveguide 57, but other signal tapping components may be used to move a portion of the outgoing LIDAR signal from the common waveguide 16 to the control waveguide 57. Examples of suitable signal tapping components include, but are not limited to, y-junctions and MMIs.

[0036] Control waveguide 57 transmits the tap signal to interferometer 58, which splits the tap signal and then recombine the different parts of the tap signal with the phase difference between the parts of the tap signal. The illustrated interferometer 58 is a Mach-Zehnder interferometer; however, other interferometers may be used.

[0037] The interferometer 58 outputs a control light signal on an interferometer waveguide 60. The interferometer waveguide 60 transmits the control light signal to a control light sensor 61, which converts the control light signal into an electrical signal used as an electrical control signal. The interferometer signal has an intensity that is a function of the frequency of the outgoing LIDAR signal. For example, the Mach-Zehnder interferometer will output a sinusoidal control light signal with a fringe pattern. A change in the frequency of the outgoing laser radar signal will result in a change in the frequency of the control light signal. Therefore, the frequency of the electrical control signal output from the control light sensor 61 is a function of the frequency of the outgoing laser radar signal. Other detection mechanisms can be used to replace the control light sensor 61. For example, the control light sensor 61 can be replaced with a balanced photodetector arranged as an optical combination component 28, a first light sensor 40, and a second light sensor 42.

[0038] The electronic device 62 can operate one or more components on the chip. For example, the electronic device 62 can communicate electrically with the light source 10, the data optical attenuator 44, the output optical attenuator 46, the first light sensor 40, the second light sensor 42, the sampling light sensor 54, and the control light sensor 61 and control their operation. Although the electronic device 62 is shown off-chip, all or part of the electronic device can be included on the chip. For example, the chip can include an electrical conductor that connects the first light sensor 40 in series with the second light sensor 42.

[0039] During operation of the chip, the electronic device 62 operates the light source 10 so that the laser cavity outputs an outgoing LIDAR signal. The electronic device 62 then operates the chip through a series of cycles, wherein each cycle generates at least a distance data point. During each cycle, the data signal is sampled multiple times. During each sampling, the electronic device tunes the frequency of the outgoing LIDAR signal. As will be described in more detail below, the electronic device can use the output from the control branch to control the frequency of the outgoing LIDAR signal so that the frequency of the outgoing LIDAR signal is known to the electronic device as a function of time. In some instances, the cycle includes a first sampling and a second sampling. During the first sampling, the electronic device 62 can increase the frequency of the outgoing LIDAR signal, and during the second sampling, the electronic device 62 can reduce the frequency of the outgoing LIDAR signal. For example, the laser cavity can be configured to output an outgoing LIDAR signal (and correspondingly the LIDAR output signal) having a wavelength of 1550nm. During a first sampling period, the electronics 62 may increase the frequency of the outgoing LIDAR signal (and accordingly the LIDAR output signal) such that the wavelength decreases from 1550 nm to 1459.98 nm, and subsequently decrease the frequency of the outgoing LIDAR signal such that the wavelength increases from 1459.98 nm to 1550 nm.

[0040] When the frequency of the outgoing LIDAR signal increases during the first sampling period, the LIDAR output signal propagates away from the chip and then returns to the chip as the LIDAR input signal. A portion of the LIDAR input signal becomes the comparison signal. During the time when the LIDAR output signal and the LIDAR input signal are propagating between the chip and the reflective object, the frequency of the outgoing LIDAR signal continues to increase. Since a portion of the outgoing LIDAR signal becomes the reference signal, the frequency of the reference signal continues to increase. As a result, the comparison signal enters the optical combination component at a lower frequency than the reference signal that simultaneously enters the optical combination component. In addition, the farther the reflective object is located from the chip, the more the frequency of the reference signal increases before the LIDAR input signal returns to the chip. Therefore, the greater the difference between the frequency of the comparison signal and the frequency of the reference signal, the farther the reflective object is from the chip. As a result, the difference between the frequency of the comparison signal and the frequency of the reference signal is a function of the distance between the chip and the reflective object.

[0041] For the same reason, when the frequency of the outgoing LIDAR signal during the second sampling period decreases, the comparison signal enters the light combining assembly at a higher frequency than the reference signal that simultaneously enters the light combining assembly, and the difference between the frequency of the comparison signal and the frequency of the reference signal during the second sampling period is also a function of the distance between the chip and the reflecting object.

[0042] In some instances, the difference between the frequency of the comparison signal and the frequency of the reference signal may also be a function of the Doppler effect, since the relative movement of the chip and the reflecting object may also affect the frequency of the comparison signal. For example, the Doppler effect may affect the frequency of the comparison signal when the chip is moving toward or away from the reflecting object and / or the reflecting object is moving toward or away from the chip. Since the frequency of the comparison signal is a function of the speed at which the reflecting object is moving toward or away from the chip and / or the speed at which the chip is moving toward or away from the reflecting object, the difference between the frequency of the comparison signal and the frequency of the reference signal is also a function of the speed at which the reflecting object is moving toward or away from the chip and / or the speed at which the chip is moving toward or away from the reflecting object. Therefore, the difference between the frequency of the comparison signal and the frequency of the reference signal is a function of the distance between the chip and the reflecting object, and is also a function of the Doppler effect.

[0043] The composite sample signal and the data signal both effectively compare the comparison signal to the reference signal. For example, because the optical combining component combines the comparison signal and the reference signal, and these signals have different frequencies, there is a jitter between the comparison signal and the reference signal. Therefore, the composite sample signal and the data signal have a beat frequency related to the frequency difference between the comparison signal and the reference signal, and the beat frequency can be used to determine the difference in the frequency of the comparison signal and the reference signal. A higher beat frequency of the composite sample signal and / or the data signal indicates a higher difference between the frequencies of the comparison signal and the reference signal. As a result, the beat frequency of the data signal is a function of the distance between the chip and the reflecting object, and is also a function of the Doppler effect.

[0044] As described above, the beat frequency is a function of two unknowns; the two unknowns are the distance between the chip and the reflecting object and the relative speed of the chip and the reflecting object (i.e., the contribution of the Doppler effect). The change in the frequency difference (Δf) between the comparison signal and the reference signal is given by Δf=2Δvf / c, where f is the frequency of the LIDAR output signal and, correspondingly, the reference signal, Δv is the relative speed of the chip and the reflecting object, and c is the speed of light in air. The use of multiple different samples permits the electronic device 62 to solve two unknown problems. For example, the beat frequency determined for the first sample is related to the unknown distance and the Doppler contribution, and the beat frequency determined for the second sample is also related to the unknown distance and the Doppler contribution. The availability of two relationships allows the electronic device 62 to solve two unknown problems. Therefore, the distance between the chip and the reflecting object can be determined without being affected by the Doppler effect. In addition, in some instances, the electronic device 62 uses the distance in combination with the Doppler effect to determine the speed of the reflecting object toward or away from the chip.

[0045] In instances where the relative velocity of the target and source is zero or very small, the contribution of the Doppler effect to the beat frequency is substantially zero. In these instances, the Doppler effect does not contribute substantially to the beat frequency, and the electronics 62 can take only the first sample to determine the distance between the chip and the reflecting object.

[0046] During operation, the electronic device 62 can adjust the frequency of the outgoing LIDAR signal in response to the electrical control signal output from the control light sensor 61. As described above, the amplitude of the electrical control signal output from the control light sensor 61 is a function of the frequency of the outgoing LIDAR signal. Therefore, the electronic device 62 can adjust the frequency of the outgoing LIDAR signal in response to the amplitude of the control. For example, when changing the frequency of the outgoing LIDAR signal during a sample, the electronic device 62 can have a range of suitable values ​​of the electrical control signal amplitude as a function of time. At multiple different times during the sampling period, the electronic device 62 can compare the electrical control signal amplitude with the range of values ​​associated with the current time in the sample. If the electrical control signal amplitude indicates that the frequency of the outgoing LIDAR signal is outside the associated range of the electrical control signal amplitude, the electronic device 62 can operate the light source 10 so as to change the frequency of the outgoing LIDAR signal so that it falls within the associated range. If the electrical control signal amplitude indicates that the frequency of the outgoing LIDAR signal is within the associated range of the electrical control signal amplitude, the electronic device 62 does not change the frequency of the outgoing LIDAR signal.

[0047] During operation, the electronics 62 may adjust the attenuation level provided by the output optical attenuator 46 in response to the sampled signal from the sampled light sensor 54. For example, the electronics 62 operates the output optical attenuator 46 to increase the attenuation level in response to the amplitude of the sampled signal being above a first signal threshold, and / or to decrease the amplitude of the power reduction in response to the amplitude of the sampled signal being below a second signal threshold.

[0048] In some examples, the electronic device 62 adjusts the attenuation level provided by the output optical attenuator 46 to prevent or reduce the impact of back reflections on the performance of the laser cavity. For example, the first signal threshold and / or the second signal threshold can be optionally selected to prevent or reduce the impact of back reflections on the performance of the laser cavity. Back reflection occurs when a portion of the LIDAR input signal returns to the laser cavity as a return LIDAR signal. In some examples, about 50% of the LIDAR input signal that passes through the facet 18 returns to the laser cavity. When the power of the return LIDAR signal entering the partial return device 14 does not decrease to less than the power of the outgoing LIDAR signal emitted from the partial return device 14 ("power drop") greater than the minimum power drop threshold, the return LIDAR signal may affect the performance of the laser cavity. In the illustrated chip, the minimum power drop threshold can be about 35dB (0.03%). Therefore, when the power of the return LIDAR signal entering the partial return device 14 is no more than 35dB lower than the power of the outgoing LIDAR signal emitted from the partial return device 14, the return LIDAR signal may affect the performance of the laser cavity.

[0049] Electronics 62 may operate output optical attenuator 46 to reduce the effects of low power drops, such as when a target object is very close or highly reflective, or both. Figure 1 It is apparent that operation of the output optical attenuator 46 to increase the attenuation level reduces the power of the returning LIDAR signal entering the partial return device 14, and also reduces the power of the returning outgoing LIDAR signal at a location remote from the partial return device 14. Since the output optical attenuator 46 is located remote from the partial return device 14, the power of the outgoing LIDAR signal emitted from the partial return device 14 is not directly affected by the operation of the output optical attenuator 46. Therefore, operation of the output optical attenuator 46 to increase the attenuation level increases the level of power reduction. As a result, the electronic device can employ the optical attenuator 46 to tune the power reduction.

[0050] In addition, the amplitude of the sampled signal is related to the power drop. Figure 1 It is obvious that the amplitude of the sampled signal is related to the power of the comparison signal. Since the comparison signal is part of the LiDAR input signal, the amplitude of the sampled signal is related to the power of the LiDAR input signal. This result means that the amplitude of the sampled signal is also related to the power of the return LIDAR signal, because the return LIDAR signal is part of the LiDAR input signal. Therefore, the amplitude of the sampled signal is related to the power drop.

[0051] Since the amplitude of the sampled signal is related to the power drop, the electronic device 62 can use the amplitude of the sampled signal to operate the output optical attenuator to keep the amplitude of the comparison signal power within the target range. For example, the electronic device 62 can operate the output optical attenuator 46 to increase the amplitude of the power drop in response to the sampled signal indicating that the amplitude of the power drop is at or below the first threshold, and / or the electronic device 62 can operate the output optical attenuator 46 to reduce the amplitude of the power drop in response to the sampled signal indicating that the amplitude of the power drop is at or above the second threshold. In some instances, the first threshold is greater than or equal to the minimum power drop threshold. In one example, the electronic device 62 operates the output optical attenuator 46 to increase the amplitude of the power drop in response to the amplitude of the sampled signal being above the first signal threshold, and / or to reduce the amplitude of the power drop in response to the amplitude of the sampled signal being below the second signal threshold. The identification of (one or more) values ​​of one, two, three or four variables selected from the group consisting of the first threshold, the second threshold, the first signal threshold and the second signal threshold can be determined based on the calibration of the optical chip during the setup of the LIDAR chip system.

[0052] When the power of the composite optical signal exceeds the power threshold, the optical sensor may become saturated. When the optical sensor becomes saturated, the amplitude of the data signal reaches a maximum value that does not increase despite the additional increase in the power of the composite optical signal above the power threshold. Therefore, when the power of the composite optical signal exceeds the power threshold, data may be lost. During operation, the electronic device 62 can adjust the attenuation level provided by the data optical attenuator 44 so that the power of the composite optical signal remains below the power threshold.

[0053] As from Figure 1 It is apparent that the amplitude of the sampling signal is related to the power of the comparison signal. Therefore, the electronic device 62 can operate the data optical attenuator 44 in response to the output from the sampling signal. For example, when the amplitude of the sampling signal indicates that the power of the comparison signal is above the upper comparison signal threshold, the electronic device 62 can operate the data optical attenuator to increase the attenuation of the comparison signal, and / or when the amplitude of the sampling signal indicates that the power of the comparison signal is below the lower comparison signal threshold, the electronic device 62 can operate the data optical attenuator to reduce the attenuation of the comparison signal. For example, in some instances, when the amplitude of the sampling signal is at or above the upper comparison threshold, the electronic device 62 can increase the attenuation of the comparison signal, and / or when the amplitude of the sampling signal is at or below the upper comparison signal threshold, the electronic device 62 reduces the attenuation of the comparison signal.

[0054] As described above, the electronics 62 may adjust the attenuation level provided by the output optical attenuator 46 in response to the sampling signal. In addition to, or as an alternative to, adjusting the attenuation level provided by the output optical attenuator 46 in response to the sampling signal, the electronics 62 may adjust the attenuation level provided by the data optical attenuator 44 in response to the sampling signal.

[0055] Suitable platforms for the chip include, but are not limited to, silicon dioxide, indium phosphide, and silicon-on-insulator wafers. Figure 2 is a cross section of a portion of a chip constructed from a silicon-on-insulator wafer. A silicon-on-insulator (SOI) wafer includes a buried layer 80 between a substrate 82 and an optical transmission medium 84. In a silicon-on-insulator wafer, the buried layer is silicon dioxide, while the substrate and the optical transmission medium are silicon. The substrate of an optical platform such as an SOI wafer can be used as the base of the entire chip. For example, Figure 1 The optical components shown in FIG. 5 can be positioned on or over the top and / or sides of the substrate.

[0056] Figure 2 The portion of the chip illustrated in FIG. 8 includes a waveguide structure suitable for use with a chip constructed from a silicon-on-insulator wafer. A ridge 86 of the optical transmission medium extends away from a slab region 88 of the optical transmission medium. The optical signal is confined between the top of the ridge and the buried oxide layer.

[0057] The dimensions of the ridge waveguide are marked on Figure 2 For example, the ridge has a width labeled w and a height labeled h. The thickness of the slab region is labeled T. For LTDAR applications, these dimensions are more important than other applications because higher levels of optical power than used in other applications need to be used. The ridge width (labeled w) is greater than 1 μm and less than 4 μm, the ridge height (labeled h) is greater than 1 μm and less than 4 μm, and the slab region thickness is greater than 0.5 μm and less than 3 μm. These dimensions can apply to straight or substantially straight portions of the waveguide, curved portions of the waveguide, and (one or more) tapered portions of the waveguide. Therefore, these portions of the waveguide will be single-mode. However, in some instances, these dimensions apply to straight or substantially straight portions of the waveguide, while the curved portions of the waveguide and / or the tapered portions of the waveguide have dimensions outside of these ranges. For example, Figure 1The tapered portion of the common waveguide 16 illustrated in FIG. 1 may have a width and / or height of >4 μm, and may be in the range of 4 μm to 12 μm. Additionally or alternatively, the curved portion of the waveguide may have a reduced slab thickness so as to reduce optical losses in the curved portion of the waveguide. For example, the curved portion of the waveguide may have a ridge extending away from a slab region having a thickness greater than or equal to 0.0 μm and less than 0.5 μm. Although the above dimensions will generally provide a single-mode structure for a straight or substantially straight portion of the waveguide, they may result in multi-mode (one or more) tapered portions and / or (one or more) curved portions. Coupling between multi-mode geometries and single-mode geometries may be accomplished using a cone that does not substantially excite higher order modes. Thus, the waveguide may be constructed such that a signal transmitted in the waveguide is transmitted in single mode, even when transmitted in a waveguide portion having multi-mode dimensions. Figure 2 The waveguide structure is applicable to all or a part of a waveguide selected from the group consisting of a cavity waveguide 12, a common waveguide 16, a reference waveguide 27, a comparison waveguide 30, a first detector waveguide 36, a second detector waveguide 38, a sampling waveguide 52, a control waveguide 57 and an interferometer waveguide 60.

[0058] The light source 10 that interfaces with the common waveguide 16 may be a gain element that is a component that is separated from a chip and then attached to the chip. For example, the light source 10 may be a gain element that is attached to a chip using a flip chip arrangement.

[0059] The use of a flip chip arrangement is suitable when the light source 10 is to be interfaced with a ridge waveguide on a chip constructed from a silicon-on-insulator wafer. Examples of suitable interfaces between a flip chip gain element and a ridge waveguide on a chip constructed from a silicon-on-insulator wafer can be found in U.S. Patent No. 9,705,278, issued on July 11, 2017, and U.S. Patent No. 5,991,484, issued on November 23, 1999; each of which is incorporated herein in its entirety. The structure is suitable for use as a light source 10. When the light source 10 is a gain element, the electronic device 62 can change the frequency of the outgoing LIDAR signal by changing the current level applied through the gain element.

[0060] The attenuator may be a component that is separated from the chip and then attached to the chip. For example, the attenuator may be included on an attenuator chip that is attached to the chip in a flip chip arrangement. The use of the attenuator chip is applicable to all or a portion of an attenuator selected from the group consisting of a data attenuator and a control attenuator.

[0061] As an alternative to including the attenuator on a separate component, all or a portion of the attenuator may be integrated with the chip. For example, an example of an attenuator interfaced with a ridge waveguide on a chip constructed from a silicon-on-insulator wafer may be found in U.S. Patent No. 5,908,305, issued June 1, 1999; each of which is incorporated herein in its entirety. The use of an attenuator integrated with the chip is applicable to all or a portion of a light sensor selected from the group consisting of a data attenuator and a control attenuator.

[0062] The light sensor that interfaces with the waveguide on the chip can be a component that is separated from the chip and then attached to the chip. For example, the light sensor can be a photodiode or an avalanche photodiode. Examples of suitable light sensor components include, but are not limited to, InGaAs PIN photodiodes manufactured by Hamamatsu, located in Hamamatsu, Japan, or InGaAs APDs (avalanche photodiodes) manufactured by Hamamatsu, located in Hamamatsu, Japan. These light sensors can be located in the center of the chip, such as Figure 1 Alternatively, all or a portion of the waveguide terminating at the light sensor may terminate at a facet 18 located at the edge of the chip, and the light sensor may be attached to the edge of the chip above the facet 18 so that the light sensor receives light passing through the facet 18. The use of the light sensor as a component separate from the chip is applicable to all or a portion of the light sensors selected from the group consisting of the first light sensor 40, the second light sensor 42, the sampling light sensor 54, and the control light sensor 61.

[0063] As an alternative to the light sensor being a separate component, all or a portion of the light sensor may be integrated with the chip. Examples of light sensors interfaced with ridge waveguides on a chip constructed from a silicon-on-insulator wafer may be found, for example, in Optics Express, Vol. 15, No. 21, 13965-13971 (2007); U.S. Pat. No. 8,093,080, issued Jan. 10, 2012; U.S. Pat. No. 8,242,432, issued Aug. 14, 2012; and U.S. Pat. No. 6,108,8472, issued Aug. 22, 2000, each of which is incorporated herein in its entirety. The use of a light sensor integrated with the chip applies to all or a portion of the light sensor selected from the group consisting of the first light sensor 40, the second light sensor 42, the sampling light sensor 54, and the control light sensor 61.

[0064] Gratings can be constructed to integrate with various optical device platforms. For example, a Bragg grating can be formed in a ridge waveguide by forming grooves on top of the ridge and / or behind the ridge.

[0065] In some instances, it is desirable to scan the LIDAR output signal. The above chip structure is suitable for use with various scanning mechanisms used in LIDAR applications. For example, the output LIDAR signal can be received by one or more reflection devices and / or one or more collimation devices. One or more reflection devices can be configured to redirect and / or manipulate the LIDAR output signal so as to provide a scan of the LIDAR output signal. Suitable reflection devices include, but are not limited to, mirrors, such as mechanically driven mirrors and micro-electromechanical systems (MEMS) mirrors. One or more collimation devices provide collimation of the LIDAR output signal, and the portion of the LIDAR input signal received in the common waveguide 16 can be increased accordingly. Suitable collimation devices include, but are not limited to, single lenses and compound lenses.

[0066] Figure 3 The above chip is illustrated for use with a reflection device 90 and a collimation device 92. For example, a lens is used as a collimation device that receives a LIDAR output signal and provides collimation of the LIDAR output signal. A mirror is used as a reflection device 90 that receives the collimated LIDAR output signal and reflects the collimated LIDAR output signal in a desired direction. As illustrated by the arrow marked A, the electronics can move the mirror so as to manipulate the collimated LIDAR output signal and / or scan the collimated LIDAR output signal. The movement of the mirror can be in two or three dimensions. Suitable mirrors include, but are not limited to, mechanically driven mirrors and micro-electromechanical systems (MEMS) mirrors.

[0067] Figure 4 The above chip is illustrated for use with a reflection device 90 and a collimation device 92. For example, a mirror is used as a reflection device 90, which receives the LIDAR output signal and reflects the LIDAR output signal in a desired direction. As illustrated by the arrow marked A, the electronic device can move the mirror to manipulate the LIDAR output signal and / or scan the LIDAR output signal. A lens is used as a collimation device 92, which receives the LIDAR output signal from the mirror and provides collimation of the LIDAR output signal. The lens can be configured to move with the movement of the mirror so that the lens continues to receive the LIDAR output signal at different positions of the mirror. Alternatively, the movement of the mirror can be sufficiently limited so that the lens continues to receive the LIDAR output signal at different positions of the mirror. The movement of the mirror can be in two or three dimensions. Suitable mirrors include, but are not limited to, mechanically driven mirrors and micro-electromechanical systems (MEMS) mirrors.

[0068] Reflective devices such as MEMS mirrors can be incorporated into chips using technologies such as SOI MEMS (Silicon-On-Insulator Micro-Electro-Mechanical Systems) technology. Figure 5is a cross section of a portion of the chip taken through the longitudinal axis of the common waveguide 16. The illustrated chip is constructed on a silicon-on-insulator waveguide. The mirror groove extends to the substrate through an optical transmission medium. The mirror is positioned in the mirror groove so that the mirror receives the LIDAR output signal from the common waveguide. The lens is used as a collimating device 92, which receives the LIDAR output signal from the mirror and provides collimation of the LIDAR output signal. The lens can be configured to move with the movement of the mirror so that the lens continues to receive the LIDAR output signal at different positions of the mirror. Alternatively, the movement of the mirror can be sufficiently restricted so that the lens continues to receive the LIDAR output signal at different positions of the mirror. The electronic device can control the movement of the mirror in two or three dimensions.

[0069] Suitable electronic devices may include, but are not limited to, a controller comprising, or consisting of, an analog circuit, a digital circuit, a processor, a microprocessor, a digital signal processor (DSP), a computer, a microcomputer, or a combination thereof suitable for performing the operations, monitoring, and control functions described above. In some instances, the controller is capable of accessing a memory comprising instructions to be executed by the controller during the performance of the operations, control, and monitoring functions. Although the electronic device is illustrated as a single component in a single location, the electronic device may include multiple different components that are independent of each other and / or placed in different locations. In addition, as described above, all or a portion of the disclosed electronic device may be included on a chip, including an electronic device integrated with a chip.

[0070] Although the laser cavity is shown as being located on-chip, all or part of the laser cavity may be located off-chip. For example, the common waveguide 16 may terminate at a second facet through which an outgoing LIDAR signal may enter the common waveguide 16 from the laser cavity located off-chip.

[0071] The chip may include components in addition to those illustrated. As an example, optical attenuators (not shown) may be positioned along the first detector waveguide 36 and the second detector waveguide 38. The electronics may operate these attenuators so that the power of the first portion of the composite sample signal reaching the first light sensor 40 is the same or approximately the same as the power of the second portion of the composite sample signal reaching the second light sensor 42. The electronics may operate the attenuators in response to outputs from the first light sensor 40 indicating the power level of the first portion of the composite sample signal and the second light sensor 42 indicating the power level of the second portion of the composite sample signal.

[0072] In view of these teachings, other embodiments, combinations and modifications of the present invention will be readily apparent to those skilled in the art. Therefore, the present invention is limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above description and drawings.

Claims

1. A LIDAR system, comprising: a LIDAR chip having a common waveguide configured to guide an outgoing LIDAR signal and a LIDAR input signal, the LIDAR input signal comprising light from the LIDAR output signal after reflection from an object located outside the LIDAR system; a LIDAR chip including a coupler configured to couple a portion of an outgoing LIDAR signal from the common waveguide to a reference waveguide as a reference signal and also to couple a portion of an input LIDAR signal from the common waveguide to a comparison waveguide as a comparison signal; a LIDAR chip configured to generate a composite signal having light from a reference signal pulsed with light from a comparison signal; and An electronic device is configured to use the composite signal to generate LIDAR data including a distance between the LIDAR chip and the object.

2. The system of claim 1, wherein the LIDAR chip is a silicon-on-insulator chip.

3. The system of claim 1, wherein the common waveguide is a single mode waveguide.

4. The system of claim 1, wherein the common waveguide comprises one or more sections having multi-mode dimensions.

5. The system of claim 1, wherein the common waveguide includes a tapered portion.

6. The system of claim 1, wherein the common waveguide comprises a curved portion wherein a ridge extends away from one or more slab regions having a thickness greater than 0.5 μm.

7. The system of claim 1, wherein at least a portion of the electronics is included on a LIDAR chip.

8. The system of claim 1, wherein the LIDAR data includes a relative velocity between an object and a LIDAR chip.

9. The system of claim 1, wherein the system includes a light sensor configured to convert light from the composite signal into an electrical signal used by the electronics to generate the LIDAR data.

10. The system of claim 9, wherein the common waveguide transmits the outgoing LIDAR signal to a facet through which the outgoing LIDAR signal is emitted from the LIDAR chip; The LIDAR chip includes a control branch that taps a portion of the outgoing LIDAR signal from the common waveguide, The control branch includes a control light sensor that receives an optical signal including light from a tapped portion of the outgoing LIDAR signal.

11. The system of claim 10, wherein the electronics are configured to tune the frequency of the outgoing LIDAR signal in response to the output from the control light sensor.

12. The system according to claim 10, wherein: The LIDAR chip includes a data branch including a sampling light sensor that receives a light signal including light from the comparison signal.

13. The system of claim 12, wherein the electronics are configured to attenuate the strength of the comparison signal in response to sampling the output of the light sensor.

14. The system of claim 12, wherein the electronics are configured to attenuate the intensity of the outgoing LIDAR signal in response to sampling the output of the light sensor.

15. The system of claim 1, wherein the comparison signal excludes light from a reference signal.

16. The system of claim 1, wherein the common waveguide terminates at a facet through which outgoing LIDAR signals are emitted from the LIDAR chip, The common waveguide is further configured to receive a LIDAR input signal through the facet, the LIDAR input signal comprising light from the outgoing LIDAR signal; and The LIDAR chip includes a data branch including a light sensor that receives a light signal including light from the LIDAR input signal.

17. The system of claim 16, wherein the electronics are configured to attenuate the intensity of an optical signal in response to the output of the optical sensor, the optical signal comprising light from the LIDAR input signal.

18. The system of claim 1, wherein the common waveguide terminates at a facet through which outgoing LIDAR signals are emitted from the LIDAR chip; and An optical attenuator configured to attenuate the strength of the outgoing LIDAR signal on the common waveguide.

19. The system of claim 18, wherein a sampling light sensor that receives a light signal including light from the outgoing LIDAR signal, and The electronics are configured to operate the optical attenuator in response to the output of the sampled light sensor.

20. The system of claim 1, wherein the common waveguide receives a comparison signal comprising light from a LIDAR input signal comprising light reflected by an object located outside of the LIDAR chip, and an optical attenuator configured to attenuate the intensity of the comparison signal on the waveguide; and The LIDAR chip includes a sampling light sensor that receives a light signal including light from the comparison signal, and The electronics are configured to operate the optical attenuator in response to the output of the sampled light sensor.

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