Chiral Quantum Optics in Hot Vapor Cladded Waveguide

Alkali vapors such as rubidium are being used in many research fields such as quantum computation, nonlinear optics, magnetometer and atomics clocks. In the last few years there is a growing interest in miniaturizing Rubidium cells from centimeter scale to micro and nano scale. On top of the obvious advantages of such integration in reducing footprint and cost reduction, many other great qualities are resulted from such an approach. For example, the high confinement allows us to observe significant nonlinear effects under very low optical power levels (nano watts). Several miniaturized Rubidium systems have been demonstrated, e.g. the atomic cladded waveguide (ACWG) and coupled atomic-plamsonic systems. The combination of strong nonlinear effects and high confinement pave the way for applications such as few photons communication system by all-optical switching. Such a system will greatly benefit from the availability of an efficient integrated optical isolator.

Rubidium is a highly dichroic media due to the Zeeman effect and thus has been used to realize optical isolators. Basically, the Zeeman effect generates circular dichroism, i.e. two orthogonal circular polarizations are experiencing a large difference in absorption. While a rectangular waveguide supports quasi linear polarized modes, it has been shown in systems combining waveguides and cold atoms that due to the longitudinal electric field in highly confined waveguide, one can define the quantization axis by applying magnetic field perpendicular to the propagation direction such that an atom will experience circular polarization.

Hereby we have experimentally demonstrated the interaction between light in a guided mode, surrounding atoms and magnetic field in our ACWG. We have fabricated a miniaturized and portable device and measured the transmission through the ACWG under varying magnetics field. The obtained results are explained by numerical simulations. This device can be used as an optical isolator or as a nanoscale magnetometer.