Electrical Generation of Surface Phonon Polaritons

TL;DR

This paper proposes a novel method for electrically generating mid-infrared light by coupling longitudinal and transverse phonon polaritons in polar crystals, bypassing the need for dipole-active electronic transitions.

Contribution

It introduces a theoretical approach to generate mid-infrared photons electrically via hybridized phonon polaritons in polar dielectric crystals, expanding possibilities for mid-infrared optoelectronic devices.

Findings

Longitudinal-transverse polaritons can be efficiently generated by electrical currents.

This method enables narrowband mid-infrared photonic emission.

Potential for developing new mid-infrared optoelectronic devices.

Abstract

Efficient electrical generation of mid-infrared light is challenging because of the dearth of materials with natural dipole-active electronic transitions in this spectral region. One approach to solve this problem is through quantum-engineering of the electron dispersion to create artificial transitions, as in quantum cascade devices. In this work we propose an alternative method to generate mid-infrared light, utilizing the coupling between longitudinal and transverse degrees of freedom due to the nonlocal optical response of nanoscopic polar dielectric crystals. Polar crystals support sub-diffraction photonic modes in the mid-infrared. They also support longitudinal phonons, which couple efficiently with electrical currents through the Fr\"ohlich interaction. As we have shown in previous theoretical and experimental works, these two degrees of freedom can hybridize forming longitudinal-transverse polaritons. Here we theoretically demonstrate that longitudinal-transverse polaritons can be efficiently generated by electrical currents, leading to resonant narrowband photonic emission. This approach can therefore be utilised to electrically generate far-field mid-infrared photons in the absence of dipole-active electronic transitions, potentially underpinning a novel generation of mid-infrared optoelectronic devices.