Three-dimensional sensing of arbitrarily shaped nanoparticles by whispering gallery mode resonators.

Whispering-gallery-mode (WGM) microresonators are a promising platform for highly sensitive, label-free detection and probing of individual nano-objects. Our work expands these capabilities by providing the analysis tools required for three-dimensional (3D) characterization of arbitrarily shaped nanoparticles. Specifically, we introduce a theoretical model that describes interactions between nanoparticles and WGM resonators, taking into account effects that were often not considered, such as the elliptical polarization of the transverse-magnetic (TM) mode, the possible non-spherical shape of the nanoparticle, its finite size, and the open-system nature of the modes.

Cavity ring-up spectroscopy for ultrafast sensing with optical microresonators.

Spectroscopy of whispering-gallery mode microresonators has become a powerful scientific tool, enabling the detection of single viruses, nanoparticles and even single molecules. Yet the demonstrated timescale of these schemes has been limited so far to milliseconds or more. Here we introduce a scheme that is orders of magnitude faster, capable of capturing complete spectral snapshots at nanosecond timescales-cavity ring-up spectroscopy.

Quantum optics. All-optical routing of single photons by a one-atom switch controlled by a single photon.

The prospect of quantum networks, in which quantum information is carried by single photons in photonic circuits, has long been the driving force behind the effort to achieve all-optical routing of single photons. We realized a single-photon-activated switch capable of routing a photon from any of its two inputs to any of its two outputs. Our device is based on a single atom coupled to a fiber-coupled, chip-based microresonator.

Atomic-force-controlled capillary electrophoretic nanoprinting of proteins.

The general nanoprinting and nanoinjection of proteins on non-conducting or conducting substrates with a high degree of control both in terms of positional and timing accuracy is an important goal that could impact diverse fields from biotechnology (protein chips) to molecular electronics and from fundamental studies in cell biology to nanophotonics. In this paper, we combine capillary electrophoresis (CE), a separation method with considerable control of protein movement, with the unparalleled positional accuracy of an atomic force microscope (AFM). This combination provides the ability to electrophoretically or electroosmotically correlate the timing of protein migration with AFM control of the protein deposition at a high concentration in defined locations and highly confined volumes estimated to be 2 al.