The group has been involved in a solid state photon counting research and development since 1984, when the first samples of the Single Photon Avalanche Detectors (SPADs) have been manufactured and tested. The detectors based on silicon avalanche photodiodes were intended to replace the vacuum photomultipliers as an echo signal detectors in a satellite laser ranging system. The advance in the detector manufacturing technology and the signal processing electronics within the last years resulted in an increase of the timing resolution, detector active area size increase, reduction of the dark count rate and extension of the useable wavelength range. Recently, the semiconductor technology permits to manufacture and operate the solid state photon counters on the basis of silicon, germanium, SiGe, GaAsP, GaP and InGaAsP.
Wide spectrum of applications for the solid state photon counters has been elaborated. The satellite laser ranging remains to be a principal application, the SPAD on silicon permits to range satellites with millimeter precision within the wide dynamical range. The SPAD on germanium enables the photon counting and satellite laser ranging at the eye safe laser wavelength in the near infrared region. The silicon SPADs have been adopted for Lidar for atmospheric probing and pollution monitoring for ecology and for the deep space applications, as well. The attractive applications have been found in the monitors for ecology - dust meter and the water pollution monitoring. The use of SPAD for the imaging through opaque media based on a ballistic photon approach has been demonstrated. The applications of solid state photon counters for fiber optics, optic communication, quantum cryptography, spectroscopy and sensors are under development.