Supercontinuum (SC) generation based on ultrashort pulse compression constitutes one of the most promising technologies towards ultra-wide bandwidth, high-brightness, and spatially coherent light sources for applications such as spectroscopy and microscopy. Here, multi-octave SC generation in a gas-filled hollow-core antiresonant fiber (HC-ARF) is reported spanning from 200 nm in the deep ultraviolet (DUV) to 4000 nm in the mid-infrared (mid-IR) having an output energy of 5 μJ. This was obtained by pumping at the center wavelength of the first anti-resonant transmission window (2460 nm) with ~100 fs pulses and an injected pulse energy of ~8 μJ. The mechanism behind the extreme spectral broadening relies upon intense soliton-plasma nonlinear dynamics which leads to efficient soliton self-compression and phase-matched dispersive wave (DW) emission in the DUV region. The strongest DW is observed at 275 nm which corresponds to the calculated phase-matching wavelength of the pump. Furthermore, the effect of changing the pump pulse energy and gas pressure on the nonlinear dynamics and their direct impact on SC generation was investigated. This work represents another step towards gas-filled fiber-based coherent sources, which is set to have a major impact on applications spanning from DUV to mid-IR.

In this paper, we numerically investigate various hollow-core anti-resonant (HC-AR) fibers towards low propagation and bend loss with effectively single-mode operation in the telecommunications window. We demonstrate how the propagation loss and higher-order mode modal contents are strongly influenced by the geometrical structure and the number of the anti-resonant cladding tubes. We found that 5-tube nested HC-AR fiber has a wider antiresonant band, lower loss, and larger higher-order mode extinction ratio than designs with 6 or more anti-resonant tubes. A loss ratio between the higher-order modes and fundamental mode, as high as 12,000, is obtained in a 5-tube nested HC-AR fiber. To the best of our knowledge, this is the largest higher-order mode extinction ratio demonstrated in a hollowcore fiber at 1.55 μm. In addition, we propose a modified 5-tube nested HC-AR fiber, with propagation loss below 1 dB/km from 1330 to 1660 nm. This fiber also has a small bend loss of ~15 dB/km for a bend radius of 1 cm.

We investigate various methods for extending the simple analytical capillary model to describe the dispersion and loss of anti-resonant hollow-core fibers without the need of detailed finite-element simulations across the desired wavelength range. This poor-man's model can with a single fitting parameter quite accurately mimic dispersion and loss resonances and anti-resonances from full finite-element simulations. Due to the analytical basis of the model it is easy to explore variations in core size and cladding wall thickness, and should therefore provide a valuable tool for numerical simulations of the ultrafast nonlinear dynamics of gas-filled hollow-core fibers.

As technology continues to advance, the development of novel sensing systems opens up new possibilities for low cost, practical biosensing applications. In this paper, we demonstrate a localized surface plasmon resonance (LSPR) system that combines both wave-guiding and plasmonic resonance sensing with a single microstructured polymeric structure. Characterizing the sensor using Finite Element Method (FEM) simulation results show a record wavelength sensitivity (WS) of 111000 nm/RIU, high amplitude sensitivity (AS) of 2050 RIU −1 , high sensor resolution and limit of detection (LOD) of 9 × 10 −7 RIU and 8.12 × 10 −12 RIU 2 /nm respectively. Furthermore, these sensors have the capability to detect an analyte within the refractive index (RI) range of 1.33 to 1.43 in the visible to mid-IR therefore being potentially suitable for applications in biomolecular and chemical analyte detection.

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A hollow-core fiber with nested anti-resonant node-free cladding tubes suitable for broadband THz guidance with low transmission losses is proposed. It is shown that the tube separation and tube thickness of the inner elements have a significant effect on the confinement loss and effective material loss of these fibers in the THz band. Using TOPAS copolymer, the proposed fiber was optimized for operation at 1 THz and it is predicted from numerical simulations that loss can be reduced to as low as 0.05 dB/m with a 0.6 THz wide dispersion flattened bandwidth.

In this Letter, we demonstrate a high pulse energy and linearly polarized mid-infrared Raman fiber laser targeting the strongest absorption line of C O 2 at ∼ 4.2 µ m . This laser was generated from a hydrogen ( H 2 )-filled antiresonant hollow-core fiber, pumped by a custom-made 1532.8 nm Er-doped fiber laser delivering 6.9 ns pulses and 11.6 kW peak power. A quantum efficiency as high as 74% was achieved, to yield 17.6 µJ pulse energy at 4.22 µm. Less than 20 bar H 2 pressure was required to maximize the pulse energy since the transient Raman regime was efficiently suppressed by the long pump pulses.

We propose and numerically analyze various hollow-core antiresonant fiber (HC-ARF) for operation at terahertz frequencies. We compare typical HC-ARF designs with nested and adjacent nested designs while analyzing performance in terms of loss and single-mode guidance of terahertz waves. With optimized fiber dimensions, the fundamental core mode, cladding mode, core higher-order modes (HOMs), and the angle dependence of adjacent tubes are analyzed to find the best design for low loss terahertz transmission. Analysis of the fiber designs shows that the nested tube-based antiresonant fiber exhibits lower transmission loss and superior HOM suppression, exceeding 140. The nested HC-ARF is feasible for fabrication using existing fabrication technologies and opening up the possibility of efficient transmission of terahertz waves.