A 32-channel photon counting module with embedded auto/cross-correlators for real-time parallel fluorescence...

Area of Science:

• Biophysics
• Spectroscopy
• Instrumentation

Background:

• Fluorescence Correlation Spectroscopy (FCS) is crucial for studying biomolecular interactions and diffusion.
• Fast FCS requires parallel data acquisition and analysis, often using Single Photon Avalanche Diode (SPAD) arrays and correlators.

Purpose of the Study:

• To develop and characterize a compact, high-throughput instrument for fast FCS.
• To investigate and mitigate distortions caused by SPAD array artifacts in FCS measurements.

Main Methods:

• Development of a 32-channel Field-Programmable Gate Array (FPGA) based correlator.
• Integration of the correlator with a 32x1 SPAD array module.
• Analysis of auto- and cross-correlation functions over a lag-time range of 10 ns to 150 ms.
• Investigation of afterpulsing and optical crosstalk effects inherent to SPAD arrays.

Main Results:

• A 32-channel FPGA correlator capable of simultaneous auto/cross-correlations was implemented.
• The correlator, integrated with a SPAD array, forms a compact instrument for high-throughput FCS.
• The impact of SPAD afterpulsing and optical crosstalk on correlation functions was assessed.

Conclusions:

• The developed instrument enables high-throughput FCS experiments with parallel data processing.
• Understanding and addressing SPAD array limitations are essential for accurate FCS data.
• Potential workarounds for SPAD-related distortions were evaluated to enhance measurement reliability.