Photonics – Counters, Detectors, SPCM (Single Photon Counting Module)

Optical sensors are devices that detect and measure changes in light intensity or other optical properties, such as polarization, phase, or wavelength. Photonics refers to the science and technology of generating, detecting, and manipulating photons (the fundamental unit of light).

Counters, detectors, and single photon counting modules (SPCMs) are examples of commonly used optical sensors in a variety of applications. A counter is a device that counts the number of photons that pass through a specific point in space within a given period of time. They are often used in photon counting experiments, such as quantum cryptography and fluorescence microscopy.

A detector is a device that converts the energy of an incident photon into an electrical signal. There are several types of detectors, including photodiodes, photomultiplier tubes (PMTs), and charge-coupled devices (CCDs). Photodiodes are semiconductor-based detectors that generate a current proportional to the intensity of the incident light. PMTs are vacuum tube-based detectors that use the electron multiplication effect to amplify the initial signal generated by a photocathode. CCDs are arrays of tiny light-sensitive pixels used to capture images or perform spectral analysis.

Single photon counting modules (SPCMs) are highly sensitive detectors capable of efficiently detecting single photons. They consist of a single-photon avalanche diode (SPAD) and associated readout electronics. SPCMs are commonly used in applications such as quantum cryptography, quantum key distribution, and quantum entanglement experiments.