Nanojunctions*

The ability to combine continuously-tunable narrow-band terahertz (THz) generation that can access both far-infrared and mid-infrared regimes, with nanometer-scale spatial resolution, holds great potential for uncovering the underlying light-matter interactions as well as realizing selective control of rotational or vibrational resonances in nanoscale objects. Here, we report selective difference frequency generation with over 100 THz bandwidth through femtosecond optical pulse shaping. The THz emission is generated at nanoscale junctions at the interface of LaAlO₃/SrTiO₃ defined by conductive atomic force microscope lithography, with the potential to perform THz spectroscopy on individual nanoparticles or molecules. Numerical simulation of the time-domain signal helps to identify different contributing components for the THz generation. These results transform the LaAlO₃/SrTiO₃ interface into a promising platform for integrated lab-on-chip devices.