Highly intense monocycle terahertz vortex generation by utilizing a Tsurupica spiral phase plate

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.

Generation of high-quality terahertz OAM mode based on soft-aperture difference frequency generation

“…In recent years, we have developed a spiral phase plate (SPP) formed of a polymeric material, dubbed Tsurupica, with an extremely low-frequency dispersion (dn/dν = -5.1×10 -4 /THz) and high transmission (0.4-0.94 cm -1 ) in the THz frequency region (1-6 THz), and we have successfully generated monochromatic 2 and 4 THz vortex outputs with topological charges of ℓ = 1 and 2 at high conversion efficiencies of over 70% and 50%, respectively [54]. The generation of a monocycle THz vortex mode [55] with ultrahigh intensity has also been demonstrated by employing the SPP in combination with tilted-pulse-front optical rectification [56]. Such a SPP is typically designed for a specific frequency; therefore, it inherently constrains the wavelength tunability of the THz vortex modes.…”

Optical vortex with a small core and Gaussian intensity envelope for light-matter interaction

“…When the optical vortex grating is created with broadband pulses of a high peak power (e.g. 2.3 MW), an SPP with high transmission and low dispersion [23] could be utilized.…”

“…z 0 is the phase retardation term in the Gouy phase. While the Laguerre function and r | | terms are frequently used in describing an optical vortex with a large optical vortex core [2,3,[23][24][25][26][27][28][29], take note of its absence in Eq. 9.…”

Vortex terahertz wave generation in air by femtosecond optical vortex pulses

“…[5][6][7][8][9] On the other hand, special light fields, such as optical vortex, 10 radially polarized, 11 Bessel 12, 13 and Airy beams 14 are widely studied and employed in various fields. 15,16 Previous attempts on vortex generation at the THz frequencies [17][18][19][20][21][22][23][24] were exclusively based on manipulation of THz wave by external components which are inherently limited in terms of acceptable bandwidth. Therefore, alternative methods for ultra-broadband vortex generation at THz frequencies should be proposed and investigated.…”