Katsuhiko Miyamoto
Professor, Chiba University, Japan

Frequency-versatile THz vortices generation based on difference frequency generation

An optical vortex has a spatial profile of annular intensity and an orbital angular momentum characterized by a topological charge, ℓ. This enables us to investigate various research fields, such as optical trapping, optical communications, and the fabrication of chiral structured materials. Specifically, the utilization of terahertz (THz) vortex has the potential to enhance spectroscopic capabilities by enabling the two-dimensional identification of biomaterials with a superior spatial resolution that beyond the diffraction limit. Various optical devices, such as a molded phase plate and a spiral phase plate (SPP), have already been used to show the creation of THz vortices through wavefront modulation. However, the frequency tunability of THz vortices is restricted due to their inherent specificity to a particular frequency. We herein propose a frequency-tunable THz (2–6 THz) vortex source with ℓTHz = 1 or 2 by employing a 1.5 µm optical vortex pumped 4’-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) difference frequency generator (DFG).