In this review, we introduce photonic crystal fibre as a novel optofluidic microdevice that can be employed as both a versatile chemical sensor and a highly efficient microreactor. We demonstrate that it provides an excellent platform in which light and chemical samples can strongly interact for quantitative spectroscopic analysis or photoactivation purposes. The use of photonic crystal fibre in photochemistry and sensing is discussed and recent results on gas and liquid sensing as well as on photochemical and catalytic reactions are reviewed. These developments demonstrate that the tight light confinement, enhanced light-matter interaction and reduced sample volume offered by photonic crystal fibre make it useful in a wide range of chemical applications.

We study the ultrafast switching-on and -off of planar GaAs/AlAs microcavities. Up to 0.8% refractive index changes are achieved by optically exciting free carriers at λ = 1720 nm and pulse energy EPump = 1.8±0.18 µJ. The cavity resonance is dynamically tracked by measuring reflectivity versus time delay with tunable laser pulses, and is found to shift by as much as 3.3 linewidths within a few ps. The switching-off occurs with a decay time of ∼ 50 ps. We derive the dynamic behavior of the carrier density, and of the complex refractive index. We propose that our inferred 10 GHz switching rate may be tenfold improved by optimized sample growth.

The exceptionally large polarizability 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. However, if they are to be used routinely in applications, a major requirement is their integration into technically feasible, miniaturized 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.

Optical fibre sensors make use of diverse physical effects to measure parameters such as strain, temperature and electric field. Here we introduce a new class of reconfigurable fibre sensor, based on a 'flying-particle' optically trapped inside a hollow-core photonic crystal fibre and illustrate its use in electric field and temperature sensing with high spatial resolution. The electric field distribution near the surface of a multi-element electrode is measured with a resolution of similar to 100 mu m by monitoring changes in the transmitted light signal due to the transverse displacement of a charged silica microparticle trapped within the hollow core. Doppler-based velocity measurements are used to map the gas viscosity, and thus the temperature, along a hollow-core photonic crystal fibre. The flying-particle approach represents a new paradigm in fibre sensors, potentially allowing multiple physical quantities to be mapped with high positional accuracy over kilometre-scale distances

In optical fiber telecommunications, there is much current work on the use of orbital angular momentum (OAM) modes for increasing channel capacity. Here we study the properties of a helically twisted photonic crystal fiber (PCF) that preserves the chirality of OAM modes of the same order, i.e., it inhibits scattering between an order +1 mode to an order -1 mode. This is achieved by thermally inducing a helical twist in a PCF with a novel three-bladed Y-shaped core. The effect is seen for twist periods of a few millimeters or less. We develop a novel scalar theory to analyze the properties of the twisted fiber, based on a helicoidal extension to Bloch wave theory. It yields results that are in excellent agreement with full finite element simulations. Since twisted PCFs with complex core structures can be produced in long lengths from a fiber drawing tower, they are of potential interest for increasing channel capacity in optical telecommunications, but the result is also of interest to the photonic crystal community, where a new kind of guided helical Bloch mode is sure to excite interest, and among the spin-orbit coupling community. (C) 2014 Optical Society of Americ