Photon-Number-Resolved Counting via Amplitude Segmentation
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Solution Overview
Problem
Conventional time-correlated single-photon counting (TCSPC) systems face challenges with pulse pile-up and coinciding photon detection, leading to artifacts and longer measurement times, especially in fast fluorescence lifetime imaging and spectroscopy applications, due to the inability to distinguish between different detection signal amplitudes and the loss of 'early' photons.
Innovation Solution
A system combining a photon-number-resolving detector with comparators adjusted to different reference values, conversion electronics to generate digital detection events with time and photon-number codes, and recording electronics to store these events, allowing for the resolution of detection signals and avoidance of pulse pile-up by encoding the amplitude of detection signals for the detected photon number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional TCSPC electronics are used, then the system is simple and easy to operate, but it cannot distinguish between different detection signal amplitudes leading to pulse pile-up artifacts
Solution Approach 1:
The detection signal is segmented by amplitude thresholding using multiple comparators, each detecting a specific photon number range. This divides the continuous amplitude signal into discrete photon number categories, enabling precise photon number resolution while maintaining manageable electronic complexity through modular comparator design.
Solution Approach 2:
The system transitions from temporal dimension analysis (time-correlated single-photon counting) to amplitude dimension analysis by utilizing the amplitude information of detection signals. This dimensional shift enables direct photon number resolution through amplitude discrimination, complementing the existing time-correlated measurement capabilities.
2Productivity
If measurements are performed at low count rates to avoid pulse pile-up, then measurement accuracy is maintained, but measurement time increases significantly
Solution Approach 1:
The system replaces the mechanical constraint of low count rate operation with an electronic solution - amplitude-based photon number resolution through comparators. This substitution allows high count rate measurements while maintaining accuracy by electronically distinguishing piled-up photons from single photons based on their amplitude signatures.
Solution Approach 2:
The system changes the operational parameter from low count rate to high count rate by utilizing amplitude discrimination. By measuring signal amplitude rather than relying on low photon flux, the system achieves both high productivity (fast measurement) and high measurement precision (accurate photon counting) simultaneously.
3Loss of information
If early photons are counted in conventional TCSPC, then they contribute to measurement data, but they are lost due to pulse pile-up effects
Solution Approach 1:
The system performs preliminary amplitude discrimination at the moment of photon detection using comparators. By immediately categorizing each detection signal's amplitude, the system prevents information loss of early photons before they can be lost to pulse pile-up effects, enabling accurate reconstruction of temporal photon arrival patterns.
Solution Approach 2:
The comparators act as intermediary devices that mediate between the raw detection signal and the final photon number determination. This intermediary amplitude analysis stage preserves information about early photons by distinguishing their amplitude characteristics even when pile-up occurs, reducing information loss without requiring overly complex post-processing.
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 faster measurement times, up to 10 to 100 times faster than conventional single-photon-counting systems, by accurately resolving photon numbers and reducing artifacts, allowing for precise analysis of fluorescence lifetimes at higher count rates.
Implementation Method 1
a photon-number-resolving detector (1) connected to a plurality of comparators (5)... capable of detecting single photons... Each detected photon generates an electrical signal of finite duration at the output of the detector
Data Source
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AI summary
The invention relates to a system for time-correlated photon-number-resolved counting applications, the system comprising the following components: - A photon-number-resolving detector (1) connected to - A plurality of comparators (5), wherein each comparator (5) is adjusted to a different reference value (Vref), wherein each comparator (5) is configured to output a comparator-signal (102) in the event that the modulus of a received detection signal (100, 101) from the photon-number-resolving detector (1) exceeds the modulus of the reference value (Vref) of the comparator (5); - A conversion electronics (8) configured to receive the comparator-signals (102) from the plurality of comparators (5) and to generate a digital detection event for each detection signal (100) of the photon-number-resolving detector (1), wherein each detection event comprises a time code (104) for the detection event comprising a time information of the detection signal (100) and an associated photon-number code (105) obtained from the number of coinciding comparator-signals (5); - A recording electronics (9), wherein the recording electronics (9) is configured to record the time code (104) of the detection event and the associated photon-number code (105), wherein the reference values (Vref) of the comparators (5) are adjusted such that a photon number for each detection signal (100) can be resolved by the system. The invention further relates to a method for time-correlated photon-number-resolved counting applications as well as to a method for adjusting the reference values for the comparators (5) of the system. Furthermore, a file structure for storing data acquired from time-correlated photon-number-resolved counting applications is disclosed.