Atomic vapor cells meet integrated optics

Abstract

The demonstration of slow, fast, and stopped light1 has helped generate considerable interest in quantum interference effects. In addition to producing intriguing physical phenomena, these effects will be valuable for future optical communications. Buffers using slow-light modules will be important elements in alloptical data networks. Cryptography systems may also be expected to use quantum interference effects for photon creation and detection. But if slow-light buffers and quantum cryptography are to be practical in real-world applications, wemust create miniaturized, stand-alone quantum interference modules. This is the aim of research involving on-chip atomic vapor cells integrated with optical waveguides Slow-light effects are a product of a medium with large, frequency-dependent gain or absorption features that then give rise to large dispersion characteristics. Our work employs quantum interference effects in atomic vapor to create large dispersion. At present, atomic vapor can provide excellent dispersion characteristics, but it usually requires a large system footprint. In classical optical setups, which beam a laser through a transparent vapor cell, there is also a constant trade-off between focal depth and beamwidth. By using on-chip hollow-core optical antiresonant reflecting optical waveguides (ARROWs), we are able to direct light down vapor-filled cores, maintaining large optical intensities over long distances. This is particularly beneficial for nonlinear optical effects that can be exploited for single-photon generation and detection. In addition, ARROW-based platforms also require only a small footprint (1×1cm). ARROWs are constructed by growing alternating layers of silicon oxide and silicon nitride around a sacrificial core on a silicon wafer. The alternating dielectric materials with specific thicknesses confine and guide light through antiresonance. After etching out the sacrificial core, we are left with a hollow channel into which we can introduce various gases and liquids for optical experiments. Solid waveguides etched into the silicon on Figure 1. A rubidium (Rb)-loaded ARROW atomic vapor cell.