Silica-based photonic crystal fibre has proven highly successful for supercontinuum generation, with smooth and flat spectral power densities. However, fused silica glass suffers from strong material absorption in the mid-infrared (>2,500 nm), as well as ultraviolet-related optical damage (solarization), which limits performance and lifetime in the ultraviolet (<380 nm). Supercontinuum generation in silica photonic crystal fibre is therefore only possible between these limits. A number of alternative glasses have been used to extend the mid-infrared performance, including chalcogenides, fluorides and heavy-metal oxides, but none has extended the ultraviolet performance. Here, we describe the successful fabrication (using the stack-and-draw technique) of a ZBLAN photonic crystal fibre with a high air-filling fraction, a small solid core, nanoscale features and near-perfect structure. We also report its use in the generation of ultrabroadband, long-term stable, supercontinua spanning more than three octaves in the spectral range 200-2,500 nm

We report a novel source of twin beams based on modulational instability in highpressure argon-filled hollow-core kagomé-style photonic-crystal fibre. The source is Raman-free and manifests strong photon-number correlations for femtosecond pulses of squeezed vacuum with a record brightness of ~2500 photons per mode. The ultrabroadband (~50 THz) twin beams are frequency tunable and contain one spatial and less than 5 frequency modes. The presented source outperforms all previously reported squeezed-vacuum twin-beam sources in terms of brightness and low mode content.PACS numbers: (42.50.Ar) Photon statistics and coherence theory, (42.50.Dv) Quantum state engineering and measurements, (42.50.Lc) Quantum fluctuations, quantum noise, and quantum jumps, (42.65.Lm) Parametric down conversion and production of entangled photons 2 Correlated photons and twin beams, among very few accessible nonclassical states of light, are at the focus of modern quantum optics. Their applications in quantum metrology [1][2][3][4], imaging [5][6][7], key distribution [8] and other fields make them the basic resource in photonic quantum technologies. Entangled photon pairs can be generated by parametric downconversion (PDC) or four-wave mixing (FWM) sources. Depending on the pumping strength, the state emerging at the output of the nonlinear material is called squeezed vacuum (SV) at low photon flux [9], or bright squeezed vacuum (BSV) at high photon flux [10]. The mean field of such states is zero, while the mean energy can approach high values.In twin-beam SV, there is strong correlation in the photon numbers emitted into the two conjugated beams (called signal and idler). At low photon flux, this simply means that the emitted photons come rarely but always in pairs. For BSV, the numbers of photons emitted into signal and idler beams are very uncertain but always exactly the same. The standard technique for detecting photon-number correlations in this case is to measure the noise reduction factor (NRF), which is the variance of the photon-number difference between the signal and idler channels, normalized to the shot-noise level, i.e., the mean value of the total photon numberwhere , si NN are the photon numbers in the signal and idler modes. NRF is a measure of the reduction of quantum noise below the shot-noise level, which corresponds to NRF = 1. Section 2). Their proximity to the pump makes them normally difficult to use due to degradation of the lower-frequency sideband by photons Raman-scattered from the pump [18,19,20].The generation of SV by FWM or MI is described by a Hamiltonian similar to the one for PDC (see Supplementary Section 1). In such a system the mean number of photons per mode is given by, assuming the pump is undepleted [24]. The parametric gain G is proportional to the pump power, the optical path-length in the nonlinear material and the χnonlinearity [25]. Despite originating from the same fundamental mechanism, the properties of FWM and MI are substantially different, justifying distinguishing the two processe...

Precise knowledge of the group velocity dispersion in gas-filled hollow-core photonic crystal fiber is essential for accurate modeling of ultrafast nonlinear dynamics. Here we study the validity of the capillary approximation commonly used to calculate the modal refractive index in kagomé-style photonic crystal fibers. For area-preserving core radius a(AP) and core wall thickness t, measurements and finite element simulations show that the approximation has an error greater than 15% for wavelengths longer than 0.56√(a(AP)t), independently of the gas-filling pressure. By introducing an empirical wavelength-dependent core radius, the range of validity of the capillary approximation is extended out to a wavelength of at least 0.98√(a(AP)t).

CHX with an ADS did not prevent plaque or gingivitis development. In fact, the CHX mouthwash with an ADS showed no superior effect over placebo on oral hygiene or the prevention of gingivitis.