Geiger-mode Avalanche Photodiode Spectrometer Wavelength Estimation
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Solution Overview
Problem
Geiger-mode avalanche photodiodes (GMAPs) face challenges in detecting subsequent photons due to self-sustaining avalanche ionization, which prevents them from continuously detecting photons after the initial photon is absorbed, requiring quenching circuits to inhibit ionization and restore biasing voltage.
Innovation Solution
A spectrometer design that includes a Geiger-mode avalanche photodiode with a semiconductor body having regions of different conductivity types, forming depleted regions, and electronic components to generate and analyze delay signals between photon detection and emission, allowing for statistical distribution analysis and wavelength estimation using theoretical probability functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reverse-biasing voltage is set higher than breakdown voltage to enable single-photon detection, then detection sensitivity is improved, but the avalanche ionization becomes self-sustaining and prevents detection of subsequent photons
Solution Approach 1:
The patent extracts and removes minority charge carriers from the quasi-neutral regions before they can trigger spurious avalanche events. This is achieved by applying a forward bias to the second junction, which creates an electric field that sweeps out these carriers, thereby eliminating the harmful effect while maintaining the high reverse bias needed for single-photon detection sensitivity
Solution Approach 2:
The patent changes the biasing parameters of the photodiode structure by introducing a dual-junction configuration where the first junction is reverse-biased above breakdown voltage for sensitive detection, while the second junction is forward-biased to control carrier populations. This parameter change allows simultaneous optimization of detection sensitivity and continuous operation capability
2Productivity
If quenching circuits are used to inhibit ionization and restore biasing voltage, then continuous detection is enabled, but device complexity increases
Solution Approach 1:
The patent implements a self-service mechanism where the photodiode structure itself, through its internal dual-junction design and appropriate biasing, automatically manages the charge carrier populations. The forward-biased second junction continuously sweeps out minority carriers, eliminating the need for external active quenching circuits and their associated complexity
Solution Approach 2:
The second junction acts as an intermediary element that mediates between the high reverse bias of the first junction and the need to control charge carriers. By being forward-biased, it creates a carrier-sweeping mechanism that protects the detection process without requiring complex external quenching circuitry
3Measurement precision
If depleted region is extended throughout the entire first region, then detection accuracy is improved, but response time increases due to carrier transit time
Solution Approach 1:
The patent segments the photodiode structure into multiple regions with different doping levels and biasing conditions. The first region is fully depleted for accurate wavelength determination, while the introduction of a second junction with forward bias creates additional functional zones that manage carrier dynamics, effectively segmenting the detection and carrier management functions
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
Enables continuous detection of photons by reducing the impact of minority charge carriers from quasi-neutral regions, improving response time and allowing for accurate wavelength determination of light sources.
Implementation Method 1
generation of a single electron-hole pair, caused by absorption within the depleted region of a photon incident on the SPAD, can be sufficient to trigger a process of ionization. This process of ionization in turn causes an avalanche multiplication of the charge carriers
Implementation Method 2
generation of a single electron-hole pair, caused by absorption within the depleted region of a photon incident on the SPAD
Implementation Method 3
electronic converter means configured for receiving the electrical detection signal and the electrical synchrony signal, and for generating an electrical delay signal, indicating delays between the instants of detection and the corresponding instants of emission
Data Source
AI summary
A spectrometer including: a photodiode having a depleted region and generating an electrical detection signal indicating instants of detection of optical pulses; a converter generating an electrical delay signal, indicating delays between the instants of detection and corresponding instants of emission of the optical pulses; a memory, storing a theoretical function corresponding to the probability of triggering an avalanche by a charge carrier generated in the depleted region; and a computing stage which determines a statistical distribution of the delays between the instants of detection and the corresponding instants of emission; selects a Gaussian portion of the statistical distribution; calculates the ratio between the sum of the number of delays of the Gaussian portion and the sum of the number of delays of the statistical distribution; and determines an estimate of the wavelength of the optical pulses on the basis of the theoretical function and of the sample value.