Over 100-THz bandwidth selective difference frequency generation at LaAlO3/SrTiO3 nanojunctions

Abstract

The ability to combine continuously tunable narrow-band terahertz (THz) generation that can access both the far-infrared and mid-infrared regimes with nanometer-scale spatial resolution is highly promising for identifying underlying light-matter interactions and realizing selective control of rotational or vibrational resonances in nanoparticles or molecules. Here, we report selective difference frequency generation with over 100 THz bandwidth via femtosecond optical pulse shaping. The THz emission is generated at nanoscale junctions at the interface of LaAlO 3 /SrTiO 3 (LAO/STO) that is 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 facilitates the identification of components that contribute to the THz generation. This ultra-wide-bandwidth tunable nanoscale coherent THz source transforms the LAO/STO interface into a promising platform for integrated lab-on-chip optoelectronic devices with various functionalities.

Gate-tunable optical extinction of graphene nanoribbon nanoclusters

“…𝑉 SD creates a quasi-static electric field 𝐸 ⃗ SD across the junction that is highly confined in space to ~10 nm, while input optical fields 𝐸 ⃗ 𝑜𝑝𝑡 (𝜔 1 ), 𝐸 ⃗ 𝑜𝑝𝑡 (𝜔 2 ) are sharply peaked in the time domain. The three electric fields mix to generate the nonlinear response of the nanojunction 32 . The power spectrum 𝑆(𝛺) versus frequency 𝛺 is calculated by taking a Fourier transform of the photoresponse 𝛥𝑉(𝜏) with respect to τ.…”

“…LaAlO3/SrTiO3 (LAO/STO) nanostructures are able to characterize the nonlinear optical response of materials like graphene 27 , and have a variety of interesting optical and electronic properties themselves 28 . A wide range of LAO/STO-based optoelectronic devices have been created using conductive atomic force microscope lithography 29 , including 10 nm-scale photodetectors 30 and nanoscale terahertz (THz) sources and detectors with >100 THz bandwidth 31,32 . Previously, the THz response of LAO/STO nanojunctions has been coupled to the plasmonic degrees of freedom in single gold plasmonic nanorods 33 .…”

Selective excitation of one among the three peaks of tip‐enhanced Raman spectroscopy by a shaped ultrafast laser pulse

“…Femtosecond laser pulse shaping is an effective method for coherent control of Raman scattering by modulating the laser spectral phase and/or amplitude. This results in constructive/destructive interference between different path integrals . This method has been widely used in controlling the molecular vibration state, rotation state, ionization state, isomerization, and other molecular dynamics.…”

Gate-Tunable Optical Nonlinearities and Extinction in Graphene/LaAlO3/SrTiO3 Nanostructures

“…LAO/STO has a tunable conductive interface 23 with a variety of interesting physical properties 24 . When the LAO thickness is close to the critical thickness for a metal-insulator transition, ∼3-4 unit cells 25 , the conductivity of the LAO/STO interface can be controlled using conductive atomic force microscope (c-AFM) lithography 14,26 .A wide range of optoelectronic devices can be fabricated at the LAO/STO interface in this fashion, such as a 10 nm-scale photodetector 27 and nanoscale, terahertz (THz) sources and detectors 28,29 with a bandwidth of more than 100 THz. LAO/STO nanostructures can be placed within two nanometers of an active graphene device and used, for example, to create reconfigurable edge channels in graphene 22 .…”