A simple and compact reflective refractometer based on a tilted fiber Bragg grating (TFBG) inscribed in an ultra-high photon-sensitive thin-core fiber is proposed and experimentally demonstrated. The reflective refractometer utilizes a short piece of thin-core fiber containing one TFBG to ensure the recoupling of cladding modes. The reflection spectra occur in two well-defined wavelength bands ...

A hollow-core fiber using anisotropic anti-resonant tubes in the cladding is proposed for low loss and effectively single-mode guidance. We show that the loss performance and higher-order mode suppression is significantly improved by using symmetrically distributed anisotropic anti-resonant tubes in the cladding, elongated in the radial direction, when compared to using isotropic, i.e. circular...

We describe erbium-ytterbium co-doped fiber lasers in different free-running and tunable configurations. The lasers were cladding-pumped by high-power multimode diode sources. We compare pumping at 915 and 980 nm. With a free-running laser, we obtained slope efficiencies of up to 50% with 915-nm pumping and 38% with 980-nm pumping, with respect to absorbed pump power. We reached a double-ended ...

A tunable negative-tap photonic microwave filter using a cladding-mode coupler together with optical injection locking of large wavelength detuning is demonstrated. Continuous and precise tunability of the filter is realized by physically sliding a pair of bare fibers inside the cladding-mode coupler. Signal inversion for the negative tap is achieved by optical injection locking of a single-mod...

Photonic crystal cavities enable the realization of high Q-factor and low mode-volume resonators, with typical architectures consisting of a thin suspended periodically-patterned layer to maximize confinement of light by strong index guiding. We investigate a heterostructure-based approach comprising a high refractive index core and lower refractive index cladding layers. Whilst confinement typ...

During loss-of-coolant (LOCA) accidents the primary reactor coolant system shall be maintained in a safe state so that the coolability of fuel rods was maintained and the emergency core cooling criteria must be met. These criteria were accepted originally for Western design reactors and the same criteria were applied in Hungary to the Paks NPP as well. However the WER type reactor has different...

A fiber-optic vector vibroscope based on orthogonal polarization cladding-to-core recoupling is demonstrated. A compact structure in which a short section of polarization-maintained (PM) fiber stub containing a straight fiber Bragg grating (FBG) is spliced to another single-mode fiber. Two well-defined orthogonally polarized cladding modes reflected by the PM-FBG are recoupled at the junction a...

An electrically controllable fiber Bragg grating (FBG) with polarization-dependent characteristics is described. The optic axis of a liquid crystal (LC) can be rearrangeable by means of external electric fields, which results in the change of an effective refractive index of an LC. The reflectivity and Bragg wavelength of an LC-cladding FBG can be controlled according to the refractive index of...

Alkali vapours, such as rubidium, are being used extensively in several important fields of research such as slow and stored light nonlinear optics quantum computation, atomic clocks and magnetometers. Recently, there is a growing effort towards miniaturizing traditional centimetre-size vapour cells. Owing to the significant reduction in device dimensions, light-matter interactions are greatly ...