Abstract: Disclosed are improved LiDAR systems and methods that achieve an improved signal-to-noise by interrogating a sub-region of a scene with an optical signal. An instantaneous field-of-view (FOV) of each detector pixel is narrowed along a first direction to reduce detection of solar-generated photons. Instantaneous FOVs of the pixels are compressed along the first direction to provide a composite FOV that is narrower than a total FOV. To sample the total FOV of a scene, the optical signal and composite FOV of the receiver are scanned across the scene along the first direction.

Abstract: A method for developing a map of objects in a region surrounding a location is disclosed. The method includes interrogating the region along a detection axis with a series of optical pulses and detecting reflections of the optical pulses that originate at objects located along the detection axis. A multi-dimensional map of the region is developed by scanning the detection axis about the location in at least one dimension. The reflections are detected via a single-photon detector that is armed using a sub-gating scheme such that the single-photon detector selectively detects photons of reflections that originate only within each of a plurality of zones that collectively define the detection field. In some embodiments, the optical pulses have a wavelength within the range of 1350 nm to 1390 nm, which is a spectral range having a relatively high eye-safety threshold and a relatively low solar background.

Abstract: A method for computing the intensity of light incident on a photodiode capable detecting single photons comprises using arrival-time statistics for a plurality of detected single photons. The statistics are based on the determination of the arrival time for each detected photon relative to the beginning of a detection period within an image frame in which the photon is detected. In some embodiments, Poisson statistics are applied to the computation of the intensity. By computing the intensity of light in this manner for each of plurality of single-photon photodetectors that compose a focal plane array, a high-contrast image of a scene can be developed.

Abstract: A method for developing a map of objects in a region surrounding a location is disclosed. The method includes interrogating the region along a detection axis with a series of optical pulses and detecting reflections of the optical pulses that originate at objects located along the detection axis. A multi-dimensional map of the region is developed by scanning the detection axis about the location in at least one dimension. The reflections are detected via a single-photon detector that is armed using a sub-gating scheme such that the single-photon detector selectively detects photons of reflections that originate only within each of a plurality of zones that collectively define the detection field. In some embodiments, the optical pulses have a wavelength within the range of 1350 nm to 1390 nm, which is a spectral range having a relatively high eye-safety threshold and a relatively low solar background.

Abstract: A negative feedback avalanche diode for detecting the receipt of a single photon is described. The photodetector comprises a load element having two load states, one characterized by high impedance and the other characterized by low impedance. The load state of the load element is controlled by a control signal generated within the negative feedback avalanche diode itself.

Abstract: A single-photon receiver is presented. The receiver comprises two SPADs that are monolithically integrated on the same semiconductor chip. Each SPAD is biased with a substantially identical gating signal. The output signals of the SPADs are combined such that capacitive transients present on each output signal cancel to substantially remove them from the output signal from the receiver.

Abstract: Methods for forming a buried p-n junction and avalanche photodiodes incorporating same are disclosed. The method includes forming a well in a semiconductor layer, wherein a depth of the well is selected as a function of the desired shape of the p-n junction in the edge region of the avalanche photodiode. A diffusion mask is then formed on the semiconductor layer, wherein the diffusion mask includes at least two openings per APD formed, wherein one opening is a diffusion window and the other is a diffusion sink. The depth of the p-n junction in the active region of the APD is based, in part, on an attribute of the diffusion mask relating to the diffusion sink.

Abstract: A single-photon receiver and method for detecting a single-photon are presented. The receiver comprises a SPAD that receives a gating signal having a fundamental frequency in the 100 MHz to multiple GHz range. The receiver further comprises a two-stage frequency filter for filtering the output of the SPAD, wherein the filter has: (1) a notch filter response at the fundamental frequency; and (2) a low-pass filter response whose cutoff frequency is less than the first harmonic of the fundamental frequency. As a result, the frequency filter removes substantially all the frequency components in the SPAD output without significant degradation of the signal quality but with reduced complexity, cost, and footprint requirement relative to receivers in the prior art.

Abstract: A negative feedback avalanche diode for detecting the receipt of a single photon is described. The photodetector comprises a load element having two load states, one characterized by high impedance and the other characterized by low impedance. The load state of the load element is controlled by a control signal generated within the negative feedback avalanche diode itself.

Abstract: A single-photon receiver and method for detecting a single-photon are presented. The receiver comprises a SPAD that receives a gating signal having a fundamental frequency in the 100 MHz to multiple GHz range. The receiver further comprises a two-stage frequency filter for filtering the output of the SPAD, wherein the filter has: (1) a notch filter response at the fundamental frequency; and (2) a low-pass filter response whose cutoff frequency is less than the first harmonic of the fundamental frequency. As a result, the frequency filter removes substantially all the frequency components in the SPAD output without significant degradation of the signal quality but with reduced complexity, cost, and footprint requirement relative to receivers in the prior art.

Abstract: A single-photon receiver is presented. The receiver comprises two SPADs that are monolithically integrated on the same semiconductor chip. Each SPAD is biased with a substantially identical gating signal. The output signals of the SPADs are combined such that capacitive transients present on each output signal cancel to substantially remove them from the output signal from the receiver.

Abstract: Avalanche photodiodes and methods for forming them are disclosed. The breakdown voltage of an avalanche photodiode is controlled through the inclusion of a diffusion sink that is formed at the same time as the device region of the photodiode. The device region and diffusion sink are formed by diffusing a dopant into a semiconductor to form a p-n junction in the device region. The dopant is diffused through a first diffusion window to form the device region and a second diffusion window to form the diffusion sink. The depth of the p-n junction is based on an attribute of the second diffusion window.

Abstract: Methods for forming a buried p-n junction and avalanche photodiodes incorporating same are disclosed. The method includes forming a well in a semiconductor layer, wherein a depth of the well is selected as a function of the desired shape of the p-n junction in the edge region of the avalanche photodiode. A diffusion mask is then formed on the semiconductor layer, wherein the diffusion mask includes at least two openings per APD formed, wherein one opening is a diffusion window and the other is a diffusion sink. The depth of the p-n junction in the active region of the APD is based, in part, on an attribute of the diffusion mask relating to the diffusion sink.

Abstract: A method for aligning a first substrate relative to a second substrate by enabling reflow of low-melting-temperature solder bumps is disclosed. Reflow of the solder bumps induces a force that moves one substrate relative to the other to improve alignment accuracy between bond pads located on each substrate. The method further enables reduction of surface oxide on the solder bumps that would otherwise inhibit reliable solder joint formation.

Abstract: The present invention enables the detection of light using an APD that has high gain and/or a wide range of operating temperature. A first APD is biased with a voltage bias that is controlled based on the breakdown voltage of a second APD, which is thermally coupled with the first APD. Changes in the breakdown voltage of the second APD due to aging, temperature chances, and the like, are reflective of changes in the breakdown voltage of the first APD. As a result, the first APD can be operated with greater stability and reliability at high gain and over larger temperature excursions than APDs known in the prior art.

Abstract: A single-photon avalanche detector is disclosed that is operable at wavelengths greater than 1000 nm and at operating speeds greater than 10 MHz. The single-photon avalanche detector comprises a thin-film resistor and avalanche photodiode that are monolithically integrated such that little or no additional capacitance is associated with the addition of the resistor.

Abstract: A focal plane array suitable for use in hyperspectral imaging applications is provided. The focal plane array comprises pixels comprising arrays of photodiodes, wherein each photodiode in each array is selectively sensitive to a different wavelength of a set of wavelengths.

Abstract: An imaging sensor having sensitivity at the single-photon level is disclosed. The sensor comprises an array of pixels, each of which comprises a negative-feedback avalanche diode and a read-out circuit that includes a counter. The counter keeps track of the number of photons detected by the diode during a given time period.

Abstract: Avalanche photodiodes and methods for forming them are disclosed. The breakdown voltage of an avalanche photodiode is controlled through the inclusion of a diffusion sink that is formed at the same time as the device region of the photodiode. The device region and diffusion sink are formed by diffusing a dopant into a semiconductor to form a p-n junction in the device region. The dopant is diffused through a first diffusion window to form the device region and a second diffusion window to form the diffusion sink. The depth of the p-n junction is based on an attribute of the second diffusion window.

Abstract: Avalanche photodiodes and methods for forming them are disclosed. The breakdown voltage of an avalanche photodiode is controlled through the inclusion of a diffusion sink that is formed at the same time as the device region of the photodiode. The device region and diffusion sink are formed by diffusing a dopant into a semiconductor to form a p-n junction in the device region. The dopant is diffused through a first diffusion window to form the device region and a second diffusion window to form the diffusion sink. The depth of the p-n junction is based on an attribute of the second diffusion window.