Two-State Negative Feedback Avalanche Diode for High-Speed Photon Detection
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Solution Overview
Problem
Current single-photon avalanche detectors (SPADs) face challenges in achieving high operational speed and wavelength range, particularly in detecting photons beyond 1000 nm, due to issues with afterpulsing and the tradeoff between quenching and re-arming times, which limits their sensitivity and efficiency in applications like quantum computing and high-performance imaging.
Innovation Solution
A dual-state feedback system is integrated with the SPAD, featuring a feedback element that switches between high and low impedance states to facilitate rapid quenching and re-arming, allowing for high-speed operation without the need for external circuitry, thereby reducing afterpulsing and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single-photon avalanche detector uses a single-state feedback load for quenching, then the quenching function is provided, but the re-arming time is prolonged due to the RC time constant
Solution Approach 1:
The feedback load is transformed from a static single resistance value to a dynamic two-state system that can switch between a first resistance value (for quenching) and a second resistance value (for re-arming). This dynamic adjustment allows the system to optimize performance for different operational phases, reducing the RC time constant during re-arming while maintaining effective quenching capability.
Solution Approach 2:
The resistance parameter of the feedback load is changed between two distinct states: a first resistance value during quenching and a second resistance value during re-arming. This parameter change enables the system to overcome the trade-off between quenching effectiveness and re-arming speed by adapting the load resistance to the current operational requirement.
2Reliability
If the feedback load resistance is increased to improve quenching, then quenching effectiveness is improved, but the RC time constant increases slowing down re-arming
Solution Approach 1:
The feedback load dynamically switches between a first resistance value (higher) for effective quenching and a second resistance value (lower) for fast re-arming. This dynamic behavior allows the system to achieve both quenching effectiveness and fast re-arming speed by using the appropriate resistance value at the appropriate time in the operational cycle.
3Adaptability or versatility
If external circuitry is added to control the feedback load, then dual-state functionality is achieved, but device complexity increases
Solution Approach 1:
The feedback load is controlled by a control signal generated internally by the single-photon avalanche detector itself during its operation. This self-service approach eliminates the need for external control circuitry, achieving dual-state functionality while minimizing device complexity. The detector's own operational signals are used to switch the feedback load between quenching and re-arming states.
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 enables SPADs to operate at rates greater than 10 MHz with reduced afterpulsing and improved sensitivity, maintaining high performance while minimizing complexity and cost associated with external control circuits.
Implementation Method 1
As the free-charge carriers travel through the multiplication region, they collide with other electrons and holes bound in the atomic lattice, thereby generating more free-charge carriers through a process called 'impact ionization.'
Implementation Method 2
When operated in 'Geiger mode,' an APD can be made sensitive enough to detect even a single photon, and a device designed specifically for this purpose is referred to as a single-photon avalanche diode (SPAD). In Geiger-mode operation, a SPAD is 'armed' by biasing it with a voltage that is above its breakdown voltage, which is the voltage bias level above which free-charge carrier generation can become self-sustaining and result in a run-away avalanche.
Implementation Method 3
A dual-state feedback system is integrated with the SPAD, featuring a feedback element that switches between high and low impedance states to facilitate rapid quenching and re-arming
Data Source
AI summary
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.