Hollow-core Photonic Bandgap Fiber Research Articles

Hollow-core photonic bandgap fibers based on a square lattice cladding

We propose a novel air-guiding photonic bandgap fiber based on a square lattice cladding. The fiber presents a 20% wider bandgap than is achievable with a conventional triangular-lattice-based cladding and with the choice of a nine-cell core can be effectively single moded at all wavelengths within the bandgap.

Molding light flow from photonic band gap circuits to microstructured fibers

The authors demonstrate nearly lossless, broadband coupling of light between photonic band gap (PBG) circuits and photonic crystal fibers (PCFs) using two-dimensional design paradigms. A hollow-core PBG fiber yields a coupling efficiency of better than 94% over a bandwidth of 25% of the center frequency, with peak transmittance exceeding 98%. A small-mode-area PCF consisting of a subwavelength solid core with nonadiabatic taper, combined with a PBG beam collimator at the air-waveguide exit port, yields over 98% coupling efficiency over a bandwidth of 135nm centered at a wavelength of 1.5μm.

Optical Guiding of Atoms through a Hollow-Core Photonic Band-Gap Fiber

We demonstrate the first guiding of atoms through a hollow-core photonic band-gap fiber. Rb atoms from a thermal oven source travel through 6.1 and 4.0 cm long fibers with a guiding potential 1/e(2) radius of 3.0 microm. When the photon scattering rate is small, the observed guiding efficiency is greater than 70%. An unexpected low-speed cutoff is attributed to inefficient optical coupling.

Saturated Optical Absorption by Slow Molecules in Hollow-Core Photonic Band-Gap Fibers

We report on saturated absorption in a hollow-core photonic band-gap fiber filled with 12C2H2 molecules. We find that slow molecules provide a major contribution to the signal in the limit of low optical power and low pressure where the signal deviates significantly from the usual Lorentzian line shape. In particular, we observe a linewidth reduction of about 3 times as compared to the transit-time limited linewidth.

Similariton fiber laser with a hollow-core photonic bandgap fiber for dispersion control

We report on an ytterbium-doped similariton fiber ring laser with a hollow-core photonic bandgap fiber for intracavity dispersion control. The oscillator is hybrid mode locked with a saturable Bragg reflector and by nonlinear polarization evolution. This scheme allows for an exact adjustment of the transmission characteristic to avoid the formation of bunched noiselike pulses while the self-starting characteristic is preserved. The oscillator generates highly stretched similaritons at 1025 nm with a pulse energy above 1n J at a repetition rate of 21.9 MHz.

Methane detection at 1670-nm band using a hollow-core photonic bandgap fiber and a multiline algorithm

The long interaction pathlengths provided by hollow-core photonic bandgap fibers (HC-PBFs) are especially advantageous for the detection of weakly absorbing gases such as methane (CH(4)). In this paper, we demonstrate methane sensing with a 1670-nm band HC-PBF. A multiline algorithm is used to fit the R(6) manifold (near 1645 nm) and, in this way, to measure the gas concentration. With this method, a minimum detectivity of 10 ppmv for the system configuration was estimated.

Micro-channels machined in microstructured optical fibers by femtosecond laser

Micro-channels were fabricated in hollow-core photonic bandgap fiber (HC-PBGF) and suspended-core holey fiber (SC-HF) by femtosecond Ti:sapphire laser irradiation. Gaseous access was demonstrated via these engineered ports to the core of HC-PBGF and the hollow cladding of SC-HF. Femtosecond laser micro-machining caused no additional transmission loss in HC-PBGFs. This allowed a novel gas cell to be produced, in which gaseous access was provided solely through two micro-channels. Acetylene diffusion was also confirmed through a micro-channel leading to a single cladding airhole in SC-HF. This further highlighted the fabrication technique's precision, selectivity, and potential for developing fiber-based micro-fluidic devices.

PMD Measurement of Hollow-Core Photonic Bandgap Fiber by Investigating Power Penalty of Optically Generated Microwave Signals

A simple method based on carrier suppression modulation for measuring first-order polarization-mode dispersion of hollow-core photonic bandgap fiber (HC-PBGF) is proposed and investigated. By adjusting the incident optical wavelength and measuring the power penalty of optically generated microwave signals, the wavelength-dependent differential group delay (DGD) in HC-PBGF can be obtained. Moreover, this proposed method is chromatic-dispersion-insensitive. The experimental results indicate that a segment of 20-m HC-PBGF exhibits highly birefringent DGD of 25, 59, and 84 ps with measurement error less than 2 ps for the incident optical wavelength of 1560, 1575, and 1580 nm, respectively

Photonic band-gap fiber gas cell fabricated using femtosecond micromachining

Femtosecond laser drilling is used to produce a variablepressure fiber gas cell. Tightly focused laser pulses are used to produce micrometer-diameter radial channels in a hollow-core photonic band-gap fiber (HC-PBGF), and through these microchannels the core of the fiber is filled with a gas. The fiber cell is formed by fusion splicing and sealing the ends of the HC-PBGF to standard step-index fiber. As a demonstration, acetylene is introduced into an evacuated fiber at multiple backing pressures and spectra are measured.

Advanced confocal microscope using single hollow-core photonic bandgap fibre design

A simple confocal microscope design based on a single hollow-core fibre approach has been developed and experimentally analysed. Key optical components are the use of a hollow-core photonic bandgap fibre and a holed-mirror beam-splitter, both of which provide significant reduction of Fresnel back-reflections at the fibre tips and total background level resulting in increased resolving confocal laser power.

Design of 7 and 19 cells core air-guiding photonic crystal fibers for low-loss, wide bandwidth and dispersion controlled operation

We study the modal properties of feasible hollow-core photonic bandgap fibers (HC-PBGFs) with cores formed by omitting either 7 or 19 central unit-cells. Firstly, we analyze fibers with thin core surrounds and demonstrate that even for large cores the proposed structures are optimum for broad-band transmission. We compare these optimized structures with fibers which incorporate antiresonant core surrounds which are known to have low-loss. Trade-offs between loss and useful bandwidth are presented. Finally, we study the effects that small modifications to the core surround have on the fiber's group velocity dispersion, showing the possibility of engineering the dispersion in hollow-core photonic bandgap fibers.

Silica-glass contribution to the effective nonlinearity of hollow-core photonic band-gap fibers

We measure the effective nonlinearity of various hollow-core photonic band-gap fibers. Our findings indicate that differences of tens of nanometers in the fiber structure result in significant changes to the power propagating in the silica glass and thus in the effective nonlinearity of the fiber. These results show that it is possible to engineer the nonlinear response of these fibers via small changes to the glass structure.

Experimental and numerical study of pulse dynamics in positive net-cavity dispersion modelocked Yb-doped fiber lasers

We report on environmentally stable mode-locked Yb-doped all-fiber lasers operating in the wave-breaking-free and stretched-pulse regime. The compact linear cavity is constructed with saturable absorber mirror directly glued to the fibers end-facet as nonlinear mode-locking mechanism and chirped fiber Bragg grating for dispersion management, thus, without any free-space optics. In the wave-breaking-free regime the laser generates positively-chirped pulses with a pulse duration of 15.4 ps. These pulses are compressed to 218 fs in a hollow-core photonic bandgap fiber spliced to the output port. Adaptation of dispersion management has led to operation in the stretched-pulse regime, where a parabolic spectral profile is obtained as well. In this regime pulses are compressible to 213 fs. Numerical simulations are presented which confirm the wave-breaking-free and stretched-pulse evolution inside the fiber laser cavity. Both regimes are compared in terms of pulse quality.

Delivery of sub-100fs pulses through 8m of hollow-core fiber using soliton compression

We report soliton compression in a tapered hollow-core photonic bandgap fiber. We compress unchirped 195fs input pulses at 800 nm wavelength to less than 100fs after single-mode propagation through 8m of fiber, at pulse energies of around 50nJ.

Numerical analysis of hollow core photonic band gap fibers with modified honeycomb lattice

An accurate analysis of the air-guiding in hollow core photonic bandgap fibers with a modified honeycomb air-hole lattice has been carried out. The influence of the hollow core dimension, as well as of the cladding geometric parameters on the confinement loss, the nonlinear coefficient and the single-mode behaviour of the fibers has been investigated through a full-vector modal solver based on the finite element method. Simulation results have shown that confinement loss lower than 0.1 dB/km, a nonlinear parameter lower than 0.01 (W · km)−1 and an effectively single-mode behaviour over a wavelength range of about 150 nm can be achieved with eight air-hole ring modified honeycomb fibers.

Hollow-core photonic bandgap fibre: new light guidance for new science and technology

We review the progress made on the fabrication and applications of hollow-core photonic crystal fibres (HC-PCFs). The mechanism of the light guidance in these fibres is described along with their dispersion properties. We review the HC-PCF fabrication, the different results achieved in the fields of laser-induced particle guidance, low-threshold stimulated Raman scattering in hydrogen (vibrational and rotational), laser frequency metrology and quantum optics. Finally, we show the different new prospects opened up by these fibres.

All-fiber picosecond laser source based on nonlinear spectral compression

The authors report the realization of an all-fiber system emitting high-quality ultrashort powerful light pulses at 1060nm. The oscillator-amplifier system is intended for compact visible light generation via frequency conversion. Optical nonlinearity in a fiber amplifier is employed to compress the spectrum of pulses negatively prechirped in a hollow core photonic bandgap fiber. Second-harmonic generation in a periodically poled crystal is demonstrated.

Optimizing the usable bandwidth and loss through core design in realistic hollow-core photonic bandgap fibers

The operational bandwidth of hollow-core photonic bandgap fibers (PBGFs) is drastically affected by interactions between the fundamental core mode and surface modes guided at the core-cladding interface. By systematically studying realistic hollow-core PBGFs we identify a new design regime robust in eliminating the presence of surface modes. We present new fiber designs with a fundamental core mode free of anticrossings with surface modes at all wavelengths within the bandgap, allowing for a low-loss operational bandwidth of ~17% of the central gap wavelength.

Arc fusion splicing of hollow-core photonic bandgap fibers for gas-filled fiber cells

The difficulty of fusion splicing hollow-core photonic bandgap fiber (PBGF) to conventional step index single mode fiber (SMF) has severely limited the implementation of PBGFs. To make PBGFs more functional we have developed a method for splicing a hollow-core PBGF to a SMF using a commercial arc splicer. A repeatable, robust, low-loss splice between the PBGF and SMF is demonstrated. By filling one end of the PBGF spliced to SMF with acetylene gas and performing saturation spectroscopy, we determine that this splice is useful for a PBGF cell.

A 158 fs 5.3 nJ fiber-laser system at 1 µm using photonic bandgap fibers for dispersion control and pulse compression

We demonstrate a 158 fs 5.3 nJ mode-locked laser system based on a fiber oscillator, fiber amplifier and fiber compressor. Dispersion compensation in the fiber oscillator was obtained with a solid-core photonic bandgap (SC-PBG) fiber spliced to standard fibers, and external compression is obtained with a hollow-core photonic bandgap (HC-PBG) fiber.