Integrated Active Quenching Circuit for High-Rate and Distortionless SPAD-Based Time-Resolved Fluorescence...

Area of Science:

• Instrumentation and Measurement Science
• Photonics and Optical Engineering

Background:

• Time-Correlated Single Photon Counting (TCSPC) is crucial for low-light detection in fluorescence lifetime imaging microscopy (FLIM) and quantum optics.
• The pile-up effect significantly distorts TCSPC measurements at high photon detection rates, limiting performance.
• Existing solutions for pile-up often involve complex post-processing or multichannel systems, complicating setups.

Purpose of the Study:

• To develop a novel Active Quenching Circuit (AQC) to mitigate the pile-up effect in TCSPC.
• To achieve distortionless TCSPC histograms at high illumination conditions by precisely controlling photodetector dead time.
• To ensure robust and precise dead time tuning resistant to environmental variations.

Main Methods:

• Development of an Active Quenching Circuit (AQC) using high-voltage 150 nm technology.
• Implementation of Process, Voltage, and Temperature (PVT) compensation for stable dead time control.
• Experimental validation using fluorescence measurements under elevated count-rate conditions.

Main Results:

• The AQC achieved a dead-time resolution of 50 ps, suitable for laser frequencies from 20 to 100 MHz.
• Demonstrated close-to-ideal linearity in dead-time control across varying conditions.
• Experimental results showed a distortion as low as 0.43% under high count-rate conditions.

Conclusions:

• The developed AQC effectively overcomes the pile-up limitation in TCSPC.
• This advancement enables more accurate and sensitive measurements in demanding optical applications.
• The circuit offers a robust and precise solution for time-resolved experiments.