Title: Difference Frequency Generation in LaAlO3/SrTiO3 Nanoscale THz Detectors
Co-authors: Lu Chen, Jianan Li, Hyungwoo Lee, Jung-Woo Lee, Chang-Beom Eom, Patrick Irvin, Jeremy Levy
Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
Pittsburgh Quantum Institute, Pittsburgh, PA, 15260 USA
Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison,
WI 53706, USA
Abstract: We investigate the broadband nonlinear detection capabilities of nano-junctions created at the interface of LaAlO3/SrTiO3 heterostructures. Using conductive AFM lithography, we define a nano-junction at the interface. We then illuminate the junction with an ultrafast femtosecond pulse laser. As a result of the large third-order nonlinear susceptibility in SrTiO3, frequency components of the ultrafast laser are mixed at the nanojunction, producing broadband radiation in THz regime. Using a pulse shaping setup with a dual-mask spatial light modulator, we shape the incoming pulse so that two wavelengths are maximized, and the rest suppressed. The nonlinear THz generation at the nano-junction enables broadband sum and difference frequency generation of these two wavelengths that has an unprecedented bandwidth of >100 THz. Access to a nanoscale THz detector with a bandwidth of this size opens pathways for a new generation of THz spectroscopy on nanomaterials.
Acknowledgements: This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. 1747452. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.