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arXiv:2606.04589

Magnetic field free nonreciprocity in tapered atomic cladded nano waveguide

Ilan Sher, Benyamin Shnirman, Arieh Grosman, Roy Zektzer, Markus Greul, Mathias Kaschel, Tilman Pfau, Robert Löw, Uriel Levy

Published Jun 3, 2026• 0 citations

Abstract

Optical nonreciprocity is a fundamental requirement for modern optical communications and quantum information processing, where it is essential to protect sensitive sources from destabilizing feedback and preserving quantum coherence. Conventional nonreciprocal devices are based on the Faraday effect; however, their dependence on bulky permanent magnets poses a significant barrier to chip-scale integration and scalability. Moreover, the application of a magnetic field is undesired in many quantum atomic systems. In this work, we demonstrate magnet-free optical nonreciprocity on a fully integrated platform utilizing a Nanophotonic Alkali Silicon Waveguide (NASWAG) interfaced with hot rubidium vapor. By employing velocity-selective optical pumping (VSOP), we break time reversal symmetry by taking advantage of the Doppler effect-generated by the thermally moving atoms, a phenomenon traditionally viewed as a limitation in atomic spectroscopy. We show that the use of suspended tapered waveguides significantly mitigates transit-time broadening, thereby enabling the observation of a robust nonreciprocal response. We further characterize the dependence of the isolation contrast on pump power, finding that the experimental measurements and numerical simulations correspond and provide mutual support for the underlying physical model. With proper optimization, the demonstrated effect may be used in the future for applications such as magnetic free optical isolators.

DOI: 10.48550/arxiv.2606.04589

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{}^{85}

Rb atoms, with the assistance of Doppler effect. This scheme may have advantages in decreasing the number of optical isolators, and thus can reduce the complexity of an integrated multiwavelength system.

Abstract Nonreciprocal devices, such as isolators, are of great importance for optical communication and optical information processing. To bypass the limitation of a strong magnetic field imposed by the traditional Faraday magneto-optic effect, many alternative mechanisms have been proposed to demonstrate magnetic-free nonreciprocity. However, limited by the drive-induced noise, the noiseless isolator capable of working in the quantum regime has yet to be realized in the experiment. Here, we show a noiseless all-optical isolator with genuine single photons in hot atoms. We experimentally study this mechanism using an open V-type level scheme and demonstrate a low insertion loss of 0.6 dB and high isolation of 30.3 dB with bandwidth up to hundreds of megahertz. Furthermore, the nonreciprocal direction can be truly reversed only by tuning the frequency of the pump laser with the same setup. Our scheme relies on widely used optical technology and is thus universal and robust.