Experimental Studies of the Near Field Enhancement Properties of Metal Resonators for Nonlinear THz Experiments*

Developing broadband sources of electromagnetic radiation in the terahertz (THz) frequency range is of current interest for studying novel magnetic phases of matter by directly coupling to the spin degrees of freedom over their intrinsic energy scale [1]. For optical studies in the nonlinear regime, sufficient THz field strengths have typically only been achieved in super-radiant linear accelerators or low-gain free-electron lasers [2]. Micron-scale metal antennas offer near-field enhancement of the incident THz field by orders of magnitude, providing table-top sources of intense THz radiation [3]. However, experimentally verifying the field enhancement from such antennas proves challenging. We present experimental studies of the field enhancement in photolithographically-patterned metallic antennas. This work provides insight into the enhancement properties of resonant metal structures and enables table-top nonlinear THz experiments.

[1] Kampfrath, T., et. al. Nature Photonics 7, 680–690 (2013).
[2] Schlauderer, S., et. al. Nature 569, 383–387 (2019).
[3] Mukai, Y. et. al. New J. Phys. 18, 013045 (2016).