Abstract: An exemplary optical measurement system includes a light source configured to emit light directed at a target. The optical measurement system further includes a photodetector configured to detect a photon of the light after the light is scattered by the target. The optical measurement system further includes a control circuit configured to receive a first input voltage that is a temperature-dependent voltage. The control circuit is further configured to receive a second input voltage that is a temperature-invariant voltage. The control circuit is further configured to output, based on a combination of the first input voltage and the second input voltage, a bias voltage for the photodetector, wherein the combination of the first and second input voltages is configured to cause the bias voltage to vary based on temperature.

Abstract: An exemplary system includes a processor, a wearable device comprising a plurality of slots, and a first module including a plurality of detectors and a module control circuit. The processor is configured to successively transmit, to each slot of the plurality of slots, a command to enable a respective module located in each slot. The processor is further configured to determine, based on an acknowledgment received from the module control circuit, that the first module is enabled and located in a first slot, and to successively transmit, based on the determining that the first module is enabled and located in the first slot, a plurality of detector address identifiers. The module control circuit is configured to successively place the plurality of detectors into an enumeration mode in which each detector of the plurality of detectors is assigned a different detector address identifier of the plurality of detector address identifiers.

Abstract: An exemplary system includes a photodetector configured to generate a photodetector output pulse when the photodetector detects a photon from a light pulse having a light pulse time period, a TDC configured to monitor for the occurrence of the photodetector output pulse during a measurement time window that is within and shorter in duration than the light pulse time period, a PLL circuit for the TDC, and a precision timing circuit connected to the PLL circuit and configured to adjust, based on at least one signal generated within the PLL circuit, a temporal position of the measurement time window within the light pulse time period.

Abstract: An exemplary system includes a PLL circuit and a precision timing circuit connected to the PLL circuit. The PLL circuit has a PLL feedback period defined by a reference clock and includes a voltage controlled oscillator configured to lock to the reference clock and having a plurality of stages configured to output a plurality of fine phase signals each having a different phase, and a feedback divider configured to be clocked by a single fine phase signal included in the plurality of fine phase signals and have a plurality of feedback divider states during the PLL feedback period. The precision timing circuit is configured to generate a timing pulse and set, based on a first combination of one of the fine phase signals and one of the feedback divider states, a temporal position of the timing pulse within the PLL feedback period.

Abstract: An exemplary optical measurement system includes a signal generator configured to generate a signal and a processing unit configured to direct the signal generator to apply the signal to a component within the optical measurement system, generate, based on a response of the component to the signal, characterization data representative of a timing uncertainty associated with the component, and perform, based on the characterization data, an action associated with the component.

Abstract: An illustrative optical measurement system includes a light source configured to emit light directed at a target, an array of photodetectors configured to detect photons of the light after the light is scattered by the target, and a processing unit. The processing unit is configured to measure a noise level of a photodetector included in the array of photodetectors and determine that the noise level meets a predetermined threshold. The processing unit is further configured to prevent, based on the determining that the noise level meets the predetermined threshold, an output of the photodetector from being used in generating a histogram based on a temporal distribution of photons detected by the array of photodetectors.

Abstract: An exemplary optical measurement system described herein includes a control circuit configured to output a global bias voltage and a module communicatively coupled to the control circuit. The module includes a light source configured to emit light directed at a target. The module further includes a plurality of detectors configured to detect arrival times for photons of the light after the light is scattered by the target. The module further includes a module control circuit configured to receive the global bias voltage and output a plurality of detector bias voltages based on the global bias voltage. The plurality of detector bias voltages include a respective detector bias voltage for each detector of the plurality of detectors.

Abstract: An illustrative optical measurement system includes a signal generator configured to generate a signal and a processing unit configured to direct the signal generator to apply the signal to a TDC included in the optical measurement system and generate, based on timestamp symbols recorded by the TDC in response to the signal, characterization data representative of a nonlinearity of the TDC.

Abstract: An exemplary wearable brain interface system includes a head-mountable component and a control system. The head-mountable component includes an array of photodetectors that includes a photodetector comprising a single-photon avalanche diode (SPAD) and a fast-gating circuit configured to arm and disarm the SPAD. The control system is for controlling a current drawn by the array of photodetectors.

Abstract: An optical measurement system includes a first wearable module comprising a first source configured to emit a first light pulse sequence comprising a plurality of light pulses and a first plurality of detectors configured to detect photons from the first light pulse sequence. The system further includes a second wearable module comprising a second source configured to emit a second light pulse sequence comprising a plurality of light pulses and that is time interleaved with the first light pulse sequence, and a second plurality of detectors configured to detect photons from the second light pulse sequence. The system further includes a control circuit configured to control light pulses emitted by the sources in accordance with time and/or frequency division multiplexing heuristics.

Abstract: An exemplary system includes an array of photodetectors and a control system. Each photodetector of the array of photodetectors may include a single-photon avalanche diode (SPAD) and a fast-gating circuit configured to arm and disarm the SPAD. The control system is configured to control a current drawn by the array of photodetectors.

Abstract: The source light having a range of optical wavelengths is split into sample light and reference light. The sample light is delivered into a sample, such that the sample light is scattered by the sample, resulting in signal light that exits the sample. The signal light and the reference light are combined into an interference light pattern having optical modes having oscillation frequency components respectively corresponding to optical pathlengths extending through the sample. Different sets of the optical modes of the interference light pattern are respectively detected, and high-bandwidth analog signals representative of the optical modes of the interference light pattern are output. The high-bandwidth analog signals are parallel processed, and mid-bandwidth digital signals are output. The mid-bandwidth digital signals are processed over an i number of iterations, and a plurality of low-bandwidth digital signals are output on the ith iteration.

Abstract: An illustrative wearable system includes a head-mountable component configured to be worn on a head of a user and a processor. The head-mountable component includes a time-to-digital converter (TDC) configured to receive, during a predetermined event detection time window that commences in response to an application of a light pulse to a target, a signal triggered by an event in which a photodetector detects a photon of the light pulse after the light pulse reflects from the target, the signal configured to enable a GRO of the TDC. The TDC is further configured to measure, using the GRO, a time interval between when the event occurred and an end of the predetermined event detection time window. The processor is configured to determine, based on the time interval and the predetermined event detection time window, an arrival time of the photon at the photodetector.

Abstract: An exemplary photodetector system includes a photodetector and a time-to-digital converter (TDC) coupled to the photodetector. The TDC is configured to receive, during a predetermined event detection time window that commences in response to an application of a light pulse to a target, a signal triggered by an event in which the photodetector detects a photon of the light pulse after the light pulse reflects from the target. The TDC is further configured to enable, in response to the receiving the signal, a gated ring oscillator (GRO) of the TDC, measure, using the GRO, a time interval between when the event occurred and an end of the predetermined event detection time window, and determine, based on the time interval and the predetermined event detection time window, an arrival time of the photon at the photodetector.

Abstract: An exemplary photodetector system includes a photodetector and a time-to-digital converter (TDC) coupled to the photodetector. The TDC is configured to receive, during a predetermined event detection time window that commences in response to an application of a light pulse to a target, a signal triggered by an event in which the photodetector detects a photon of the light pulse after the light pulse reflects from the target. The TDC is further configured to enable, in response to the receiving the signal, a gated ring oscillator (GRO) of the TDC, measure, using the GRO, a time interval between when the event occurred and an end of the predetermined event detection time window, and determine, based on the time interval and the predetermined event detection time window, an arrival time of the photon at the photodetector.

Abstract: An exemplary system includes an array of photodetectors and a control system. Each photodetector of the array of photodetectors may include a single-photon avalanche diode (SPAD) and a fast-gating circuit configured to arm and disarm the SPAD. The control system is configured to control a current drawn by the array of photodetectors.

Abstract: An exemplary photodetector system includes a plurality of photodetectors connected in parallel and a processor communicatively coupled to the plurality of photodetectors. The processor is configured to receive an accumulated output from the plurality of photodetectors. The accumulated output represents an accumulation of respective outputs from each of the plurality of photodetectors detecting photons during a predetermined measurement time period that occurs in response to a light pulse being directed toward a target within a body. The processor is further configured to determine, based on the accumulated output, a temporal distribution of photons detected by the plurality of photodetectors, and generate, based on the temporal distribution of photons, a histogram representing a light pulse response of the target within the body.

Abstract: The source light having a range of optical wavelengths is split into sample light and reference light. The sample light is delivered into a sample, such that the sample light is scattered by the sample, resulting in signal light that exits the sample. The signal light and the reference light are combined into an interference light pattern having optical modes having oscillation frequency components respectively corresponding to optical pathlengths extending through the sample. Different sets of the optical modes of the interference light pattern are respectively detected, and high-bandwidth analog signals representative of the optical modes of the interference light pattern are output. The high-bandwidth analog signals are parallel processed, and mid-bandwidth digital signals are output. The mid-bandwidth digital signals are processed over an i number of iterations, and a plurality of low-bandwidth digital signals are output on the ith iteration.

Abstract: A method for single-molecule detection is provided and uses a carbon nanotube having a probe entity attached thereto to define a first state of the carbon nanotube. The carbon nanotube is introduced to a target entity to define a second state of the carbon nanotube. The electrical conductance of the carbon nanotube in the first and second states is compared to detect the presence of a biomolecular entity. A system for single-molecule detection including a carbon nanotube is also provided.

Abstract: A method for single-molecule detection is provided and uses a carbon nanotube having a probe entity attached thereto to define a first state of the carbon nanotube. The carbon nanotube is introduced to a target entity to define a second state of the carbon nanotube. The electrical conductance of the carbon nanotube in the first and second states is compared to detect the presence of a biomolecular entity. A system for single-molecule detection including a carbon nanotube is also provided.