Refractive index describes the speed of light originating from light-matter interaction in its most linear form. Differently, the imaginary index defines nonlinear gain and alternating its sign allowed nonreciprocity. Yet, linear nonreciprocity by irreversible index, like in downstream literally dragging light (Fizeau, 1851), was never considered. As spinning devices isolate sound (Alù, 2014), one might ask why such a simple and straightforward approach was not considered for photonics applications such as optical isolation? The major technology stopper corresponds to maintaining separation between spinning cavities and couplers within tolerance-ranges of as small as several nanometers, as needed for critical coupling. But since light travels faster than sound, speeds near 360 km/hr are needed inside the resonator for isolating light. However, resonators spinning at 400,000 RPM for achieving such velocities, results in an un-tolerated wobbling, making coupling18,19 challenging. Inspired by harddrive technology of heads aerodynamically flying above disks. Here, we fabricate photonic couplers flying at nano-elevation over resonators spinning fast enough to fully split their counter-circulating optical-modes; and experimentally demonstrate that a coupled fiber turns transparent from one side, while at the same time, opaque from its other end. In the past, near zero-drag20 gas-film lubricantion21 enabled the big-data revolution22. This principle benefits here self-adjusted photonic flyers permitting 99.6% isolation in standard telecom fibers. Unlike flat geometries, the saddle-convex geometry of our bent-nanowire and sphere makes them relatively easy to bring closer; which might impact surface-science studies at nano-separations, where Casimir- and van der Walls-forces dominate, and gravity might even be examined.

Date Published: 4 March 2019
PDF
Proc. SPIE 10934, Optical, Opto-Atomic, and Entanglement-Enhanced Precision Metrology, 1093409 (4 March 2019); doi: 10.1117/12.2515413

Published in SPIE Proceedings Vol. 10934:
Optical, Opto-Atomic, and Entanglement-Enhanced Precision Metrology
Selim M. Shahriar; Jacob Scheuer, Editor(s)