Computational Hyperspectral Terahertz Holography

Abstract

The progress in terahertz (0.1-10 THz) technologies has opened access to electromagnetic waves that are extremely short in the number of oscillations. Moreover, the result of THz technologies is not the envelope or radiation power but the spatial distribution of the electric field itself. This allows to access the amplitude-phase information for all spectral components. It makes possible the development of the holographic approach which involves measurements in a wide collimated beam. Moreover, in the practical implementation of measurements, it is possible to decrease the number of optical elements for THz range, since the field is recorded by a scanning diaphragm or a wide-aperture crystal.

In the thesis the method of digital hyperspectral THz holography was developed and improved, including the description of the physical, mathematical and computational aspects. This method allows to study the spatio-temporal and spatio-spectral dynamics of electricwavefields in linear isotropic homogeneous non-magnetic medium. The developed THz holography allows also to analyze the arbitrary vector beams including the behavior of transverse and longitudinal components of the field and polarization state. The practical application of THz holography was demonstrated on example of data transmission using the interference of pairs of THz vortex beams. The low signal-to-noise ration and high level of noise problems were solved by using the block-matching algorithms adapted for three dimensional complex THz fields, thus increasing the resolution and image quality of THz hyperspectral holograms. The developed approach was also expanded to the near infrared range corresponding to femtosecond laser pulses. Here the features of correlative registration of broadband laser fields of femtosecond duration was realized using the hyperspectral holography.