Abstract-Highly nonlinear organic crystal OHQ-T for efficient ultra-broadband terahertz wave generation beyond 10 THz

Bong Joo Kang, In Hyung Baek, Seung-Heon Lee, Won Tae Kim, Seung-Jun Lee, Young Uk Jeong, O-Pil Kwon, and Fabian Rotermund
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-10-11054

We report on efficient generation of ultra-broadband terahertz (THz) waves via optical rectification in a novel nonlinear organic crystal with acentric core structure, i.e. 2-(4-hydroxystyryl)-1-methylquinolinium 4-methylbenzenesulfonate (OHQ-T), which possesses an ideal molecular structure leading to a maximized nonlinear optical response for near-infrared-pumped THz wave generation. By systematic studies on wavelength-dependent phase-matching conditions in OHQ-T crystals of different thicknesses we are able to generate coherent THz waves with a high peak-to-peak electric field amplitude of up to 650 kV/cm and an upper cut-off frequency beyond 10 THz. High optical-to-THz conversion efficiency of 0.31% is achieved by efficient index matching with a selective pumping at 1300 nm.

© 2016 Optical Society of America

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Abstract-In vivo analysis of THz wave irradiation induced acute inflammatory response in skin by laser-scanning confocal microscopy

Yoonha Hwang, Jinhyo Ahn, Jungho Mun, Sangyoon Bae, Young Uk Jeong, Nikolay A. Vinokurov, and Pilhan Kim  »View Author Affiliations

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-22-10-11465

Optics Express, Vol. 22, Issue 10, pp. 11465-11475 (2014)
http://dx.doi.org/10.1364/OE.22.011465

The recent development of THz sources in a wide range of THz frequencies and power levels has led to greatly increased interest in potential biomedical applications such as cancer and burn wound diagnosis. However, despite its importance in realizing THz wave based applications, our knowledge of how THz wave irradiation can affect a live tissue at the cellular level is very limited. In this study, an acute inflammatory response caused by pulsed THz wave irradiation on the skin of a live mouse was analyzed at the cellular level using intravital laser-scanning confocal microscopy. Pulsed THz wave (2.7 THz, 4 μs pulsewidth, 61.4 μJ per pulse, 3Hz repetition), generated using compact FEL, was used to irradiate an anesthetized mouse’s ear skin with an average power of 260 mW/cm² for 30 minutes using a high-precision focused THz wave irradiation setup. In contrast to in vitro analysis using cultured cells at similar power levels of CW THz wave irradiation, no temperature change at the surface of the ear skin was observed when skin was examined with an IR camera. To monitor any potential inflammatory response, resident neutrophils in the same area of ear skin were repeatedly visualized before and after THz wave irradiation using a custom-built laser-scanning confocal microscopy system optimized for in vivo visualization. While non-irradiated control skin area showed no changes in the number of resident neutrophils, a massive recruitment of newly infiltrated neutrophils was observed in the THz wave irradiated skin area after 6 hours, which suggests an induction of acute inflammatory response by the pulsed THz wave irradiation on the skin via a non-thermal process.

© 2014 Optical Society of America

Abstract-Generating high-power short terahertz electromagnetic pulses with multifoil radiator

Nikolay A. Vinokurov and Young Uk Jeong
http://prl.aps.org/accepted/fe071Ye2K2217a39225b2dd818ebc35e1da09eb4a
We describe a multi-foil cone radiator capable of generating high-field short terahertz pulses using short electron bunches. Round flat conducting foil plates with successively decreasing radii are stacked, forming a truncated cone with the z-axis. The gaps between the foil plates are equal and filled with some dielectric (or vacuum). A short relativistic electron bunch propagates along the z-axis. At sufficiently high particle energy, the energy losses and multiple scattering do not change the bunch shape significantly. When passing by each gap between the foil plates, the electron bunch emits some energy into the gap. Then, the radiation pulses propagate radially outward. For TEM-like waves with a longitudinal (along the z-axis) electric field and an azimuthal magnetic field, there is no dispersion in these radial lines; therefore, the radiation pulses conserve their shapes (time dependence). At the outer surface of the cone, we have synchronous circular radiators. Their radiation field forms a conical wave. Ultrashort terahertz pulses with gigawattlevel peak power can be generated with this device.