Higher-order modes are controllably excited in water-filled kagomè-, bandgap-style, and simplified hollow-core photonic crystal fibers (HC-PCF). A spatial light modulator is used to create amplitude and phase distributions that closely match those of the fiber modes, resulting in typical launch efficiencies of 10–20% into the liquid-filled core. Modes, excited across the visible wavelength range, closely resemble those observed in air-filled kagomè HC-PCF and match numerical simulations. These results provide a framework for spatially-resolved sensing in HC-PCF microreactors and fiber-based optical manipulation.
We report long-range optical binding of multiple polystyrene nanoparticles (100-600 nm in diameter) at fixed interparticle distances that match multiples of the half-beat-lengths between the lowest order modes of a hollow-core photonic crystal fiber. Analysis suggests that each nanoparticle converts the incoming optical mode into a superposition of co-propagating modes, within the beat pattern of which further particles can become trapped. Strikingly, the entire particle arrangement can be moved over a distance of several cm, without changing the inter-particle spacing, by altering the ratio of backward-to-forward optical power. Potential applications are in multi-dimensional nanoparticle-based quantum optomechanical systems.
Hollow-core photonic crystal fibre (HC-PCF) offers strong light confinement and long interaction lengths in an optofluidic channel. These unique advantages have motivated its recent use as a highly efficient and versatile microreactor for liquid-phase photochemistry and catalysis. In this work, we use a soft-glass HC-PCF to carry out photochemical experiments in a high-index solvent such as toluene. The high-intensity and strong confinement in the fibre is demonstrated to enhance the performance of a proof-of-principle photolysis reaction.
We report an electric field sensor based on a charged microparticle that is optically trapped, and moved to and
fro, inside a hollow-core photonic crystal fibre (PCF). Transverse electric fields displace the particle, altering
the transmitted optical power. The transmission change is found to be linear with fields in the 0.1-50 kV/m
range, with a flat frequency response from 0.01 to ~1 kHz. In a first test, the field pattern near a multi-element
electrode was resolved with a spatial resolution of 1 mm. This unique "flying particle" sensor allows electric
field mapping over long distances (the lowest loss hollow core PCF has a 3 dB length of ~3 km) and is
suitable for inaccessible or harsh environments.
Recent results on optomechanical and optoacoustic nonlinearities in optical fibres are reported. In a new type of a microstructured silica fibre, comprising two ultra-thin closely spaced glass waveguides, an extremely high and optically broadband optomechanical nonlinearity is shown to occur. This nonlinearity originates from the optical gradient forces between coupled waveguides, can exceed the Kerr effect by many orders of magnitude and allows the formation of stable self-trapped optical modes that represent a novel kind of optical soliton. Furthermore, optoacoustic interaction via electrostriction in the micron-sized core of a photonic crystal fibre is studied. It is demonstrated, that coherent optically-driven acoustic waves, tightly guided in the core, can facilitate in-fibre dynamic optical isolation and all-optical switching.
High-dimensional entangled photons pairs are interesting for quantum information and cryptography: Compared
to the well-known 2D polarization case, the stronger non-local quantum correlations could improve noise resistance
or security, and the larger amount of information per photon increases the available bandwidth. One
implementation is to use entanglement in the spatial degree of freedom of twin photons created by spontaneous
parametric down-conversion, which is equivalent to orbital angular momentum entanglement, this has been
proven to be an excellent model system. The use of optical fiber technology for distribution of such photons
has only very recently been practically demonstrated and is of fundamental and applied interest. It poses a
big challenge compared to the established time and frequency domain methods: For spatially entangled photons,
fiber transport requires the use of multimode fibers, and mode coupling and intermodal dispersion therein
must be minimized not to destroy the spatial quantum correlations. We demonstrate that these shortcomings
of conventional multimode fibers can be overcome by using a hollow-core photonic crystal fiber, which follows
the paradigm to mimic free-space transport as good as possible, and are able to confirm entanglement of the
fiber-transported photons. Fiber transport of spatially entangled photons is largely unexplored yet, therefore we
discuss the main complications, the interplay of intermodal dispersion and mode mixing, the influence of external
stress and core deformations, and consider the pros and cons of various fiber types.
We present ultrafast optical switching experiments on 3D photonic band gap crystals. Switching the Si inverse opal is
achieved by optically exciting free carriers by a two-photon process. We probe reflectivity in the frequency range of
second order Bragg diffraction where the photonic band gap is predicted. We observe a large frequency shift of up to
1.5% of all spectral features including the peak that corresponds to the photonic band gap. We also demonstrate large,
ultrafast shifts of stop bands of planar GaAs/AlAs photonic structures. We briefly discuss how our results can be used in
future switching and modulation applications.