P Holzer

Tunable vacuum-UV to visible ultrafast pulse source based on gas-filled Kagome-PCF.

An efficient and tunable 176-550 nm source based on the emission of resonant dispersive radiation from ultrafast solitons at 800 nm is demonstrated in a gas-filled hollow-core photonic crystal fiber (PCF). By careful optimization and appropriate choice of gas, informed by detailed numerical simulations, we show that bright, high quality, localized bands of UV light (relative widths of a few percent) can be generated at all wavelengths across this range. Pulse energies of more than 75 nJ in the deep-UV, with relative bandwidths of ~3%, are generated from pump pulses of a few μJ. Excellent agreement is obtained between numerical and experimental results. The effects of positive and negative axial pressure gradients are also experimentally studied, and the coherence of the deep-UV dispersive wave radiation numerically investigated.

Pressure-controlled phase matching to third harmonic in Ar-filled hollow-core photonic crystal fiber

We report tunable third-harmonic generation (THG) in an Ar-filled hollow-core photonic crystal fiber, pumped by broadband <2 microJ, 30 fs pulses from an amplified Ti:sapphire laser system. The overall dispersion is precisely controlled by balancing the negative dielectric susceptibility of the waveguide against the positive susceptibility of the gas. We demonstrate THG to a higher-order guided mode and show that the phase-matched UV wavelength is tunable by adjusting the gas pressure.

Influence of ionization on ultrafast gas-based nonlinear fiber optics

We numerically investigate the effect of ionization on ultrashort high-energy pulses propagating in gas-filled kagomé-lattice hollow-core photonic crystal fibers by solving an established uni-directional field equation. We consider the dynamics of two distinct regimes: ionization induced blue-shift and resonant dispersive wave emission in the deep-UV. We illustrate how the system evolves between these regimes and the changing influence of ionization. Finally, we consider the effect of higher ionization stages.

Combined soliton pulse compression and plasma-related frequency upconversion in gas-filled photonic crystal fiber

We numerically investigate self-frequency blueshifting of a fundamental soliton in a gas-filled hollow-core photonic crystal fiber. Because of the changing underlying soliton parameters, the blueshift gives rise to adiabatic soliton compression. Based on these features, we propose a device that enables frequency shifting over an octave and pulse compression from 30 fs down to 2.3 fs.

Low loss hollow optical-waveguide connection from atmospheric pressure to ultra-high vacuum

A technique for optically accessing ultra-high vacuum environments, via a photonic-crystal fiber with a long small hollow core, is described. The small core and the long bore enable a pressure ratio of over 108 to be maintained between two environments, while permitting efficient and unimpeded delivery of light, including ultrashort optical pulses. This delivery can be either passive or can encompass nonlinear optical processes such as optical pulse compression, deep UV generation, supercontinuum generation, or other useful phenomena.

4% conversion of sub-µJ near-IR pulses to deep UV in fundamental mode of Ar-filled PCF

We report extreme self-compression of sub-µJ 30 fs pulses at 800 nm in Ar-filled hollow-core PCF, resulting in 4% conversion to deep UV light in the fundamental guided mode, pressure-tunable from 220–270 nm.

Phase-matching and Gain of deep-UV dispersive-wave generation

Gas-filled hollow-core photonic crystal fibres enable nonlinear fibre optics in parameter regimes hitherto impossible with glass-core fibres, such as: ultra-violet transmission, pressure tuneable zero dispersion wavelengths down to 200 nm, and ultra-short duration soliton energies at the microjoule level. Two techniques for ultra-violet light generation in such fibres have utilised these properties: third harmonic generation [1], and dispersive wave generation [2]. In this work we study the phase-matching and gain landscapes of the latter case.

Nonlinear optics in gas-filled HC-PCF in the plasma regime

Laser-driven ionization in Ar-filled HC-PCF is accessed through self-compression of few-microjoule pulses. Modeling confirms that the observed blue-shifted spectral bands are caused by light-plasma interactions over an extended length in the fiber.

UV continuum generation in Ar-filled hollow-core PCF

We numerically model the generation, by continuous emission of dispersive waves in an Ar-filled hollow-core PCF with an axially increasing gas pressure distribution, of a UV continuum spanning 175-250 nm.

Interaction between Kerr and ionization induced nonlinear fiber optics

Light-plasma interactions are explored in gas-filled photonic crystal fibers through self-compression of few-μJ pulses. Here we study the interaction between ionization-driven soliton dynamics and Kerr-based deep-UV generation.