100 THz-bandwidth difference frequency generation at LaAlO3/SrTiO3 nanoscale junctions*

We investigate the broadband nonlinear generation and detection capabilities of nanoscale junctions created at the LaAlO3/SrTiO3 interface using conductive AFM lithography. Using the large non-resonant third-order nonlinear susceptibility in SrTiO3, strong difference frequency mixing occurs when the junction is biased, leading to induced polarization that can also be detected at the junction (Ma et al, Nano Lett 13, 2884 (2013)). Here we characterize the bandwidth of the resulting THz emission, which appears to be bandwidth limited to about 100 THz for the 7 fs Ti:Sapphire laser pulse used. The ultrawide tunable bandwidth opens pathways for a new generation of THz spectroscopy on nanomaterials.