Time Correlated Single Photon Counting, or TCSPC, is a specialised technique used to detect and measure the arrival time of individual photons with extremely high precision.
The core idea behind TCSPC is to measure the time between the emission of a photon and its detection. TCSPC has become an essential tool in a range of research fields, particularly in applications such as fluorescence lifetime imaging (FLIM), time-of-flight measurements and LiDAR.
So, what exactly is TCSPC, how does it work and why is it a game-changer in photon counting and single-photon detection?
How does TCSPC work?
The TCSPC process normally begins when a light pulse is emitted from a source such as a laser or LED. This pulse of light may interact with a sample, undergo absorption and a photon re-emitted at a different wavelength, or the pulse may simply bounce off a surface like in LiDAR. When the photon reaches the detector, the detector measures the exact time the photon arrives, which is recorded as a “time tag.” This time-tagging is central to TCSPC’s power, as it allows for extremely high temporal resolution, often down to picoseconds.
A typical TCSPC system works by generating a reference signal, or sync, at the point of photon emission and another signal when the photon is detected. The time delay between these two signals is recorded precisely. Over time, by accumulating data from many individual photons, TCSPC builds a statistical profile of photon arrival times. This enables the construction of time-resolved histograms and the extraction of important data about photon emission processes, fluorescence lifetimes or distance measurements in time-of-flight setups.
Key concepts in Time Correlated Single Photon Counting
Photon Counting
Photon counting is the foundation of TCSPC, as the technique relies on the detection of single photons. Traditional light detection methods might capture the total intensity of light over time, but photon counting focuses on individual photon events, allowing for ultra-sensitive measurements at low light levels. Photon counting also enables researchers to study light-matter interactions on a particle-by-particle basis, making TCSPC ideal for precision experiments.
Single Photon Detection
Single-photon detection is essential for TCSPC because the technique depends on capturing the precise time each photon is detected. Specialised sensors, such as SPADs (Single Photon Avalanche Diodes), photomultiplier tubes (PMTs), and SNSPDs (superconduction nanowire detectors) are typically used for this purpose. These sensors are capable of detecting individual photons and triggering the time-tagging process, providing a crucial basis for the TCSPC workflow.
Time-Tagging
Time-tagging refers to the process of assigning a precise timestamp to each detected photon. With time-tagging resolutions down to the picosecond level, researchers can capture time-resolved information that reveals intricate details about photon dynamics. In applications like fluorescence lifetime imaging, time tagging enables scientists to determine how long a molecule remains in an excited state before emitting a photon, providing insights into molecular interactions and environments.
Applications of TCSPC
TCSPC has a broad range of applications, especially in fields requiring high temporal resolution and sensitivity. Here are some of the most impactful areas:
- Fluorescence Lifetime Imaging (FLIM): FLIM uses TCSPC to measure fluorescence lifetimes, revealing information about molecular environments and cellular processes.
- Quantum Optics and Quantum Cryptography: TCSPC plays a critical role in quantum experiments, especially in the development of secure quantum communication systems.
- Time-of-Flight (ToF) Measurements: In time-of-flight applications, such as LiDAR, TCSPC provides accurate distance measurements by calculating the time photons take to travel to an object and back.
- Single Molecule Detection: TCSPC allows researchers to monitor single molecules in real time, advancing understanding in fields like biophysics and chemistry.
Photon Force Solutions for TCSPC
At Photon Force, we are committed to delivering advanced TCSPC solutions that empower researchers and innovators. Our flagship PF32 camera range is designed specifically for time-correlated single photon counting, featuring high-speed single-photon detection with exceptional temporal resolution. The PF32 cameras are ideal for applications like fluorescence imaging, quantum optics, and LiDAR, providing reliable, precise photon counting and time-tagging capabilities.
For those with specialised needs, Photon Force also offers custom modules and sensors for OEM applications. Whether you require a tailored sensor design or an integration-ready TCSPC solution, our team can design and manufacture high-performance single-photon detectors that align with your technical requirements.
By leveraging Photon Force’s cutting-edge technology, researchers and engineers can achieve the highest standards in TCSPC, helping to unlock new possibilities in science and technology. For more information on how Photon Force can support your TCSPC needs, explore our PF32 camera range and custom module or sensor offerings, or contact us to discuss your unique requirements.
