Bright upconverted emission from light-induced inelastic tunneling

Area of Science:

• Photonics and Nanotechnology
• Quantum Optics

Background:

• Conventional methods for upconverted light generation, such as harmonic generation and multi-photon luminescence, are inefficient, requiring extremely high field intensities.
• Existing light-induced inelastic tunneling emission has shown promise with 2% conversion efficiency per tunneling event.

Purpose of the Study:

• To investigate a novel mechanism for bright upconverted light emission from nanostructured metal surfaces.
• To explore the potential of light-induced inelastic tunneling emission in metal tunnel junctions for efficient light generation.

Main Methods:

• Fabrication of metal tunnel junctions.
• Excitation using a 1560 nm femtosecond pulsed laser.
• Characterization of emitted light properties, including intensity and wavelength dependence on the local electric field.
• Finite-difference time-domain (FDTD) simulations to model local electric field enhancement.

Main Results:

• Observed bright emission from metal tunnel junctions, significantly exceeding harmonic generation by 5 orders of magnitude.
• Attributed the emission to light-induced inelastic tunneling.
• Demonstrated that emission wavelength varies with the local electric field, consistent with tunneling-based phenomena.
• FDTD simulations confirmed sufficient local fields for visible light emission via inelastic tunneling.

Conclusions:

• Light-induced inelastic tunneling in metal tunnel junctions provides a highly efficient pathway for ultrafast upconverted light emission.
• This phenomenon surpasses conventional nonlinear optical processes in brightness and efficiency.
• The findings present a promising avenue for developing advanced light sources and photonic devices.