The exceptionally large polarisability of highly excited Rydberg atoms (six orders of magnitude higher than ground-state atoms) makes them of great interest in fields such as quantum optics, quantum computing, quantum simulation and metrology. If how
ever they are to be used routinely in applications, a major requirement is their integration into technically feasible, miniaturised devices. Here we show that a Rydberg medium based on room temperature caesium vapour can be confined in broadband-guiding kagome-style hollow-core photonic crystal fibres. Three-photon spectroscopy performed on a caesium-filled fibre detects Rydberg states up to a principal quantum number of n = 40. Besides small energy level shifts we observe narrow lines confirming the coherence of the Rydberg excitation. Using different Rydberg states and core diameters we study the influence of confinement within the fibre core after different exposure times. Understanding these effects is essential for the successful future development of novel applications based on integrated room temperature Rydberg systems.
We demonstrate experimentally and theoretically that a nanoscale hollow channel placed centrally in the solid glass core of a photonic crystal fiber strongly enhances the cylindrical birefringence (the modal index difference between radially and azim
uthally polarized modes). Furthermore, it causes a large split in group velocity and group velocity dispersion. We show analytically that all three parameters can be varied over a wide range by tuning the diameters of the nanobore and the core.
It is shown that, in the liquid-filled hollow core of a single-mode photonic crystal fiber, a micron-sized particle can be held stably against a fluidic counter-flow using radiation pressure, and moved to and fro (over 10s of cm) by ramping the laser
power up and down. The results represent a major advance over previous work on particle transport in optically multimode liquid-filled fibers, in which the fluctuating transverse field pattern renders the radiation and trapping forces unpredictable. The counter-flowing liquid can be loaded with sequences of chemicals in precisely controlled concentrations and doses, making possible studies of single particles, vesicles or cells.
We demonstrate a quantitative broadband fiber sensor, based on evanescent field sensing in the cladding holes of an air-suspended solid-core photonic crystal fiber. We discuss the fabrication process, together with the structural- and optical charact
erization of a range of different fibers. Measured mode profiles are in good agreement with finite element method calculations made without free parameters. The fraction of the light in the hollow cladding can be tuned via the core diameter of the fiber. Dispersion measurements are in excellent agreement with theory and demonstrate tuning of the zero dispersion wavelength via the core diameter. Optimum design parameters for absorption sensors are discussed using a general parameter diagram. From our analysis, we estimate that a sensitivity increase of three orders of magnitude is feasible compared to standard cuvette measurements. Our study applies to both liquid and gas fiber sensors. We demonstrate the applicability of our results to liquid chemical sensing by measuring the broad absorption peak of an aqueous nickel chloride solution. We find striking agreement with the reference spectrum measured in a standard cuvette, even though the sample volume has decreased by three orders of magnitude. Our results demonstrate that air-suspended solid-core PCFs can be used in quantitative broadband chemical sensing measurements.
