SPAD Sensor Dual-Mode Operation for Photon Detection Rate
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Solution Overview
Problem
The recovery time of single-photon avalanche diodes (SPADs) after triggering limits their maximum photon detection rate due to the quench time required for voltage reset, which restricts the operational range and efficiency of SPAD-based sensor systems.
Innovation Solution
Operating a SPAD in two modes: a first mode to determine light intensity and a second mode where the reverse bias voltage is adjusted based on the intensity to optimize detection, allowing for improved detection efficiency without device saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reverse bias voltage is increased to improve photon detection sensitivity, then the detection capability is improved, but the device is more prone to saturation and noise under high light intensity
Solution Approach 1:
The patent implements dynamic adjustment of the reverse bias voltage based on ambient light intensity conditions. The control circuitry continuously monitors light levels and adjusts the voltage accordingly - operating in Geiger mode with high voltage for low-light conditions to maximize single-photon detection sensitivity, and switching to linear mode with reduced voltage for high-light conditions to prevent saturation and minimize noise, thus resolving the contradiction between detection sensitivity and saturation resistance
Solution Approach 2:
The patent changes the operational parameter (reverse bias voltage) of the SPAD device based on environmental conditions. By transitioning between different voltage regimes (high voltage for Geiger mode vs. lower voltage for linear mode), the system adapts to varying light intensity conditions, improving both detection precision under low light and reliability under high light without requiring hardware modifications
2Reliability
If the quench time is extended to ensure complete carrier recombination, then the reliability of preventing after-pulses is improved, but the maximum photon detection rate is reduced
Solution Approach 1:
The patent implements dynamic quenching strategies where the quench time and voltage reset profile are adjusted based on operating conditions. The control circuitry optimizes the quench duration and voltage restoration rate to achieve sufficient carrier recombination while minimizing dead time, allowing the system to maintain high detection rates without compromising after-pulse prevention reliability
Solution Approach 2:
The patent applies preliminary voltage reduction before the avalanche event fully develops and maintains optimized voltage restoration timing after quenching. By carefully controlling the voltage profile timing and magnitude, the system ensures complete carrier recombination while minimizing the duration of the quench period, thus resolving the contradiction between reliable after-pulse prevention and maintaining high detection rates
3Measurement precision
If the SPAD operates in Geiger mode for single-photon detection, then the detection sensitivity is improved, but the operational range is limited due to saturation at higher light intensities
Solution Approach 1:
The patent makes the SPAD device multi-functional by enabling it to operate in multiple modes (Geiger mode for single-photon detection and linear mode for high-light conditions) through dynamic voltage control. This allows a single device to handle a wide range of light intensities effectively, resolving the contradiction between single-photon sensitivity and broad operational adaptability
Solution Approach 2:
The patent dynamically switches between Geiger mode and linear mode operation based on ambient light intensity. The control circuitry monitors light levels and adjusts the reverse bias voltage accordingly - maintaining high voltage for Geiger mode under low-light conditions to maximize single-photon detection, and reducing voltage to linear mode under high-light conditions to expand the operational range and prevent saturation
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 approach enhances the operational range and accuracy of SPAD-based systems by optimizing voltage settings for light intensity levels, reducing quench time, and enabling higher detection rates while avoiding saturation and noise issues.
Implementation Method 1
The high reverse bias voltage generates a sufficient electric field such that a single photon can create an electron-hole pair in the depletion layer of the device via impact ionization
Implementation Method 2
the creation of which can trigger a self-sustaining avalanche
Data Source
AI summary
A method may include operating a single-photon avalanche diode (SPAD) in a first mode to determine a light intensity level associated with the SPAD, operating the SPAD in a second mode wherein a reverse bias voltage is applied in the second mode to bias the SPAD beyond its breakdown voltage, such that the SPAD operates in a detection mode, and determining a magnitude of the bias voltage applied to the SPAD in the second mode based on the light intensity level determined in the first mode.