Recovering lossless propagation of polaritons with synthesized complex frequency excitation

TL;DR

This paper introduces a synthetic complex frequency excitation method to restore lossless propagation of phonon polaritons, overcoming intrinsic absorption losses and enhancing their practical applications in photonics.

Contribution

The study presents a novel synthetic excitation technique using virtual gain to compensate for polariton losses, enabling near-lossless propagation.

Findings

Successfully reduced intrinsic losses in phonon polaritons

Demonstrated potential for improved photonic circuit integration

Enhanced subwavelength light confinement and energy transfer

Abstract

Surface plasmon polaritons and phonon polaritons offer a means of surpassing the diffraction limit of conventional optics and facilitate efficient energy storage, local field enhancement, high sensitivities, benefitting from their subwavelength confinement of light. Unfortunately, losses severely limit the propagation decay length, thus restricting the practical use of polaritons. While optimizing the fabrication technique can help circumvent the scattering loss of imperfect structures, the intrinsic absorption channel leading to heat production cannot be eliminated. Here, we utilize synthetic optical excitation of complex frequency with virtual gain, synthesized by combining the measurements taken at multiple real frequencies, to restore the lossless propagations of phonon polaritons with significantly reduced intrinsic losses. The concept of synthetic complex frequency excitation represents a viable solution to compensate for loss and would benefit applications including photonic circuits, waveguiding and plasmonic/phononic structured illumination microscopy.