Abstract
Optical vortex, possessing an annular intensity profile and an orbital angular momentum (characterized by an integer termed a topological charge) associated with a helical wavefront, has attracted great attention for diverse applications due to its unique properties. In particular for terahertz (THz) frequency range, several approaches for THz vortex generation, including molded phase plates consisting of metal slit antennas, achromatic polarization elements and binary-diffractive optical elements, have been recently proposed, however, they are typically designed for a specific frequency. Here, we demonstrate highly intense broadband monocycle vortex generation near 0.6 THz by utilizing a polymeric Tsurupica spiral phase plate in combination with tilted-pulse-front optical rectification in a prism-cut LiNbO3 crystal. A maximum peak power of 2.3 MW was obtained for THz vortex output with an expected topological charge of 1.15. Furthermore, we applied the highly intense THz vortex beam for studying unique nonlinear behaviors in bilayer graphene towards the development of nonlinear super-resolution THz microscopy and imaging system.
Highlights
Terahertz imaging systems, which enable the assignment of various eigen frequencies of molecules and clusters[1], have been intensively investigated in a variety of fields, such as biomedicine, security, and nondestructive inspection[2,3,4,5,6,7]
Optical vortices[11,12] have an annular intensity profile, an orbital angular momentum characterized by an integer, l, and a helicity defined by the sign of the topological charge
Intense and monocycle THz vortex pulses generated by the optical rectification of femtosecond laser pulses enable the study of nonlinear phenomena, e.g., nonlinear absorption and multi-photon excitation, and have the potential to enable THz imaging with a spatial resolution of micrometers, which would allow the observation of local defects in crystalline materials such as graphene[22] and various semiconductors[23,24,25,26]
Summary
Terahertz imaging systems, which enable the assignment of various eigen frequencies (molecular fingerprints) of molecules and clusters[1], have been intensively investigated in a variety of fields, such as biomedicine, security, and nondestructive inspection[2,3,4,5,6,7]. Their spatial resolution is typically diffraction-limited to the submillimeter scale due to the relatively long wavelength of THz radiation. Several optical devices, including molded phase plates consisting of V-shaped slit antennas[27] on thin metal, achromatic polarization elements[28], and binary-diffractive optical elements[29], have been recently proposed for www.nature.com/scientificreports/
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
