G. Antonopoulos

Bio: G. Antonopoulos is an academic researcher from University of Bath. The author has contributed to research in topics: Optical fiber & Photonic-crystal fiber. The author has an hindex of 4, co-authored 13 publications receiving 1077 citations.

Stimulated Raman Scattering in Hydrogen-Filled Hollow-Core Photonic Crystal Fiber

Abstract: We report on stimulated Raman scattering in an approximately 1-meter-long hollow-core photonic crystal fiber filled with hydrogen gas under pressure. Light was guided and confined in the 15-micrometer-diameter hollow core by a two-dimensional photonic bandgap. Using a pulsed laser source (pulse duration, 6 nanoseconds; wavelength, 532 nanometers), the threshold for Stokes (longer wavelength) generation was observed at pulse energies as low as 800 ± 200 nanojoules, followed by a coherent anti-Stokes (shorter wavelength) generation threshold at 3.4 ± 0.7 microjoules. The pump-to-Stokes conversion efficiency was 30 ± 3% at a pulse energy of only 4.5 microjoules. These energies are almost two orders of magnitude lower than any other reported energy, moving gas-based nonlinear optics to previously inaccessible parameter regimes of high intensity and long interaction length.

Experimental demonstration of the frequency shift of bandgaps in photonic crystal fibers due to refractive index scaling.

Abstract: Experimental demonstration of the frequency shift of photonic bandgaps due to refractive index scaling using D2O-filled hollow-core photonic crystal fibers is presented. The results confirm a simple scaling law for bandgaps in fibers in which the low-index medium is varied.

Stokes amplification regimes in quasi-cw pumped hydrogen-filled hollow-core photonic crystal fiber.

Abstract: Pure rotational stimulated Raman scattering spectra containing nine strong spectral components were generated from a approximately 11 m long hollow-core photonic crystal fiber filled with hydrogen and pumped with nanosecond pulses having energies around 100-300 nJ. Observation of both transient and steady-state scattering threshold behavior is reported. Passage from the transient to the steady state is observed with a pulse as long as 14 ns. Convenient analytical expressions for energy and power threshold are deduced for the present configuration.

Robust plasmonic tips fabricated by the tapering of composite hybrid silicate microfibers with metallic core

Abstract: A tapered hybrid microfiber comprising a metal core and a glass silicate cladding is the platform proposed here for the development of plasmonic sensing devices. The existence of the glass cladding provides several advantages over pure metal tips while exhibiting high enhancement factors at the tip apex up to 104. Optimization of the fiber tapering process conditions can be achieved by using different metals having different melting points, viscosity and thermal expansion coefficients as well as composite fibers with different glass and metal core diameter in order to achieve tapered microwires with the desirable geometrical and operational characteristics.

Applications of hollow-core photonic crystal fiber

Abstract: We report on long-distance particle-guidance and low-threshold SRS using hollow-core photonic-crystal-fiber. A laser of 80 mW was sufficient to levitate dry particles and guide them through a 150 mm long fiber, and a 800 nJ nanosecond pump-laser generated SRS in the hydrogen-filled fiber

Photonic crystal fibers

Abstract: Photonic crystal fibers guide light by corralling it within a periodic array of microscopic air holes that run along the entire fiber length Largely through their ability to overcome the limitations of conventional fiber optics—for example, by permitting low-loss guidance of light in a hollow core—these fibers are proving to have a multitude of important technological and scientific applications spanning many disciplines The result has been a renaissance of interest in optical fibers and their uses

Supercontinuum generation in photonic crystal fiber

Abstract: A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Bound states in the continuum

Abstract: Bound states in the continuum (BICs) are waves that remain localized even though they coexist with a continuous spectrum of radiating waves that can carry energy away. Their very existence defies conventional wisdom. Although BICs were first proposed in quantum mechanics, they are a general wave phenomenon and have since been identified in electromagnetic waves, acoustic waves in air, water waves and elastic waves in solids. These states have been studied in a wide range of material systems, such as piezoelectric materials, dielectric photonic crystals, optical waveguides and fibres, quantum dots, graphene and topological insulators. In this Review, we describe recent developments in this field with an emphasis on the physical mechanisms that lead to BICs across seemingly very different materials and types of waves. We also discuss experimental realizations, existing applications and directions for future work. The fascinating wave phenomenon of ‘bound states in the continuum’ spans different material and wave systems, including electron, electromagnetic and mechanical waves. In this Review, we focus on the common physical mechanisms underlying these bound states, whilst also discussing recent experimental realizations, current applications and future opportunities for research.

Photonic-Crystal Fibers

Abstract: The history, fabrication, theory, numerical modeling, optical properties, guidance mechanisms, and applications of photonic-crystal fibers are reviewed