Microscopic optical buffering in a harmonic potential.

M Sumetsky

doi:10.1038/srep18569

Abstract

In the early days of quantum mechanics, Schrödinger noticed that oscillations of a wave packet in a one-dimensional harmonic potential well are periodic and, in contrast to those in anharmonic potential wells, do not experience distortion over time. This original idea did not find applications up to now since an exact one-dimensional harmonic resonator does not exist in nature and has not been created artificially. However, an optical pulse propagating in a bottle microresonator (a dielectric cylinder with a nanoscale-high bump of the effective radius) can exactly imitate a quantum wave packet in the harmonic potential. Here, we propose a tuneable microresonator that can trap an optical pulse completely, hold it as long as the material losses permit, and release it without distortion. This result suggests the solution of the long standing problem of creating a microscopic optical buffer, the key element of the future optical signal processing devices.

Highlights

Follows from the equidistance of the spectrum of the resonator within the spectral width of the wave packet, which can be ensured by potentials with more general spatial dependencies
We consider the resonant propagation of a whispering gallery mode (WGM) pulse corresponding to the fixed azimuthal and radial quantum numbers m and p, which is fully described by the amplitude Ψ(z, t)as a function of axial coordinate z and time t
We show that a tuneable harmonic potential well, which is reproduced by a miniature Surface Nanoscale Axial Photonics (SNAP) bottle resonator illustrated in Fig. 2, can trap an optical pulse completely, hold it as long as the material losses permit, and release without distortion

Summary

Introduction

Follows from the equidistance of the spectrum of the resonator within the spectral width of the wave packet, which can be ensured by potentials with more general spatial dependencies. In contrast to quantum mechanics, where the experimental realization of such resonators is problematic and still does not mean much in one dimension[10], essentially one-dimensional resonant structures can be realized based on the photonic crystal waveguides, sequences of ring resonators, and fibre Bragg gratings To this end, the periodicity of these structures should be appropriately chirped[12,13,14] to arrive at the locally precise equidistant spectrum. The recently developed photonic fabrication platform, Surface Nanoscale Axial Photonics (SNAP), precisely imitates the one-dimensional Schrödinger equation optically and, at the same time, does not require the subwavelength-scale modulation of the refractive index to arrive at the effective potential with required spectrum governing the slow light propagation[15,16,17]. In the final Discussion section, the feasibility of the proposed harmonic optical buffers is analysed based on the recent progress in fabrication and investigation of nonlinear and piezoelectric multimaterial optical fibres

Methods

Results

Conclusion