The laboratory conducts research in the field of methods for generating terahertz radiation, which are based on quantum processes of interaction of radiation with matter. The terhertz frequency range, located on the border of the radio and optical ranges, is very promising for the development of communication systems, information processing, "tera-vision" - the detection of hidden objects, tomography, material recognition and biomedical applications. To create sources and receivers in this range, we are developing new methods for frequency conversion of laser radiation in nonlinear crystals, photoconductive antennas, and topological insulators.
For the first time in the world, the problem of generating quantum states of radiation in the terahertz frequency range was posed. Active work is underway on the study and application of optical-terahertz biphotons - pairs of quantum-entangled photons, one of which has a terahertz frequency, and the second has an optical frequency and is easily detected by a conventional photodetector. This occurs during spontaneous parametric down-conversion (SPDC), but not in the usual, but in a strongly frequency-nondegenerate regime. The unique SPDC effect at purely optical frequencies is well known in quantum optics, is widely used in quantum technologies to create nonclassical entangled states of radiation, and is used in quantum photometry and sensorics. The transfer of quantum optical concepts to the terahertz range can give a lot of new things in the very next few years.
The first steps in the practical application of optical-terahertz biphotons in absolute quantum photometry have already been made. The use of quantum approaches can make it possible to measure the brightness of terahertz radiation, the sensitivity and quantum efficiency of terahertz detectors without the use of any pre-calibrated standards. The laboratory also solves the problems of generating and detecting terahertz radiation in photoconductive antennas based on topological insulators from the family of bismuth and antimony chalcogenides, studying the mechanisms of relaxation of surface states, creating effective nonlinear converters of higher harmonics of terahertz radiation, and studying the complex conductivity of topological insulators in the terahertz region of the spectrum.
It has been found that topological insulators, like graphene, can serve as extremely efficient frequency converters for terahertz waves.
The results obtained open up opportunities for the implementation of new sources and converters of radiation in the terahertz range, as well as for the construction of ultrafast spintronic devices based on topological insulators.