Unlike the capillaries conventionally used for gas-based spectral broadening of ultrashort (<100 fs) multi-millijoule pulses, which produce only normal dispersion at usable pressure levels, hollow-core photonic crystal fibres provide pressure-adjustable normal or anomalous dispersion. They also permit low-loss guidance in a hollow channel that is about ten times narrower and has a 100-fold-higher effective nonlinearity than capillary-based systems. This has led to several dramatic results, including soliton compression to few-cycle pulses, widely tunable deep-ultraviolet light sources, novel soliton-plasma interactions and multi-octave Raman frequency combs. A new generation of versatile and efficient gas-based light sources, which are tunable from the vacuum ultraviolet to the near infrared, and of versatile and efficient pulse compression devices is emerging

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.

We report on the spectral broadening of ~1 μJ 30 fs pulses propagating in an Ar-filled hollow-core photonic crystal fiber. In contrast with supercontinuum generation in a solid-core photonic crystal fiber, the absence of Raman and unique pressure-controlled dispersion results in efficient emission of dispersive waves in the deep-UV region. The UV light emerges in the single-lobed fundamental mode and is tunable from 200 to 320 nm by varying the pulse energy and gas pressure. The setup is extremely simple, involving <1 m of a gas-filled photonic crystal fiber, and the UV signal is stable and bright, with experimental IR to deep-UV conversion efficiencies as high as 8%. The source is of immediate interest in applications demanding high spatial coherence, such as laser lithography or confocal microscopy.

Shifts in the threshold voltage (ΔVth) of transparent zinc tin oxide (ZTO) transistors under gate bias stress are studied. The effect of composition and processing temperature on the device stability has been investigated. Based on the research, highly stable transistors with ΔVth as small as 30mV after 1000min of operation have been fabricated with a composition of [Zn]:[Sn]=36:64. As current drivers in active matrix displays their stability renders ZTO thin film transistors (TFTs) a very attractive alternative to TFTs based on established technologies.

By using a gas-filled kagome-style photonic crystal fiber, nonlinear fiber optics is studied in the regime of optically induced ionization. The fiber offers low anomalous dispersion over a broad bandwidth and low loss. Sequences of blueshifted pulses are emitted when 65 fs, few-microjoule pulses, corresponding to high-order solitons, are launched into the fiber and undergo self-compression. The experimental results are confirmed by numerical simulations which suggest that free-electron densities of ∼10(17) cm(-3) are achieved at peak intensities of 10(14) W/cm(2) over length scales of several centimeters.