Negative-feedback avalanche photodetector for single-photon sensitivity
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Solution Overview
Problem
Current infrared imaging technologies face limitations in achieving single-photon sensitivity and high dynamic range video rate operation due to analog noise, self-heating effects, and complexity in existing photodetector systems, particularly in low-light-level conditions.
Innovation Solution
The development of a focal plane array (FPA) using negative-feedback avalanche diodes (NFADs) that provide single-photon sensitivity and passive quenching, eliminating the need for external quenching circuitry and enabling high-speed operation by integrating negative feedback elements with the photodiode, allowing for digital threshold detection and counting of photons within a given time period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional p-i-n photodetectors are used for SWIR imaging, then low noise at room temperature is achieved, but single-photon sensitivity and high dynamic range video rate operation cannot be achieved
Solution Approach 1:
The patent changes the operating parameters of the photodetector by switching from linear mode to avalanche breakdown mode, and further to geiger mode with negative feedback. This parameter transformation enables single-photon sensitivity while maintaining high operational rates through passive quenching, resolving the contradiction between measurement precision and productivity.
Solution Approach 2:
The patent introduces negative feedback mechanisms in the form of parallel resistors that automatically quench avalanche events. This feedback system enables the detector to reset rapidly after each photon detection event, achieving both single-photon sensitivity and high video rate operation without external control circuitry.
2Measurement precision
If SPAD-based pixels with active quenching are used, then single-photon sensitivity is achieved, but device complexity increases due to external quenching circuitry
Solution Approach 1:
The patent implements self-service by designing the photodetector structure itself to provide quenching functionality through parallel resistors integrated within the device. The detector automatically quenches its own avalanche events without requiring external control circuitry, thereby maintaining single-photon sensitivity while eliminating device complexity associated with external quenching systems.
Solution Approach 2:
The patent merges the quenching function with the photodetector structure by integrating parallel resistors directly into the device architecture. This combination eliminates the need for separate external quenching circuitry, reducing device complexity while preserving single-photon detection capability.
3Temperature
If microbolometers are used for LWIR imaging, then thermal radiation detection is achieved, but self-heating effects and poor sensitivity occur
Solution Approach 1:
The patent replaces thermal detection mechanisms with quantum mechanical avalanche photodetection. By using photodetectors operating in avalanche breakdown mode rather than thermal microbolometers, the system achieves superior sensitivity without self-heating effects, as the detection mechanism relies on photon-induced carrier multiplication rather than thermal radiation measurement.
4Quantity of substance
If analog detection mechanisms are used, then image data accumulation is achieved, but electrical and thermal noise degrade signal-to-noise ratio
Solution Approach 1:
The patent employs periodic action by using discrete avalanche events triggered by individual photons rather than continuous analog accumulation. Each photon detection creates a distinct, quantized electrical pulse that can be counted and differentiated from noise, significantly improving signal-to-noise ratio while maintaining detection of total photon quantity over time.
Solution Approach 2:
The patent segments the continuous analog signal into discrete quantized pulses corresponding to individual photon events. By detecting and counting separate avalanche events rather than accumulating analog charge, the system achieves superior noise immunity while preserving information about total photon quantity, resolving the contradiction between quantity measurement and signal-to-noise ratio.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution significantly enhances the operational rate and reduces noise, achieving high dynamic range and single-photon resolution imaging without the complexity of active quenching circuitry, with photon detection efficiencies exceeding 25% and dark count rates below 10 kHz, enabling improved low-light-level imaging performance.
Implementation Method 1
a first photodiode, wherein the first photodiode is a single-photon avalanche diode that is physically adapted to provide a current pulse in response to a single received photon
Implementation Method 2
a first photodiode, wherein the first photodiode is a single-photon avalanche diode that is physically adapted to provide a current pulse in response to a single received photon
Implementation Method 3
a first negative feedback element, wherein the first negative feedback element is electrically connected in series with the first photodiode, and wherein the first photodiode and the first negative feedback element collectively define a negative-feedback avalanche diode
Data Source
AI summary
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.