Optical-to-terahertz switches: state of the art and new opportunities for multispectral imaging

Compact and cost-effective spectrometers and imaging systems in the terahertz (THz) frequency range based on optical-THz photoconductive converters of ultrashort laser pulses (photoconductive antennas—PCAs) are actively being developed and widely used to solve fundamental and applied problems in a variety of fields of science and technology. This high activity of research and development is associated with the PCAs' reliability and compact size, the easy scalability of a single element to 1D and 2D arrays, and PCAs' ability to provide a wide spectral range and high dynamic range of recorded THz signals without cooling. Recently, systems for multi-pixel detection of THz radiation based on matrix PCA detectors, designed to greatly increase the speed of THz imaging, have been of particular interest. This review presents the latest trends in the development of PCA-based THz devices, PCA-based methods of THz pulsed spectroscopy and imaging, as well as alternative approaches to THz pulse recording and THz imaging.