Infrared attosecond field transients and UV to IR few-femtosecond pulses generated by high-energy soliton self-compression

Infrared femtosecond laser pulses are important tools both in strong-field physics, driving X-ray high-harmonic generation, and as the basis for widely tuneable, if inefficient, ultrafast sources in the visible and ultraviolet. Although anomalous material dispersion simplifies compression to few-cycle pulses, attosecond pulses in the infrared have remained out of reach. We demonstrate soliton self-compression of 1800 nm laser pulses in hollow capillary fibers to sub-cycle envelope duration (2 fs) with 27 GW peak power, corresponding to attosecond field transients. In the same system, we generate wavelength-tuneable few-femtosecond pulses from the ultraviolet (300 nm) to the infrared (740 nm) with energy up to 25 $\mu$J and efficiency up to 12 %, and experimentally characterize the generation dynamics in the time-frequency domain. A compact second stage generates multi-$\mu$J pulses from 210 nm to 700 nm using less than 200 $\mu$J of input energy. Our results significantly expand the toolkit available to ultrafast science.Comment: 8 pages, 5 figure

Few-femtosecond deep-UV Pulses for transient-absorption experiments

In this thesis I describe the development, implementation and characterisation of a source of wavelength-tunable few-femtosecond laser pulses in the deep ultraviolet spectral region for use in time-resolved experiments. I also propose and model an extension of this source capable of simultaneously generating a single-cycle driving pulse for extreme nonlinear optics as well as a few-femtosecond ultraviolet pulse. Building on advances in the field of femtochemistry, ultrafast science is moving towards ever shorter timescales and more complex systems. One of the key building blocks for the next generation of experiments studying ultrafast dynamics in molecules will be the availability of few-femtosecond pulses to directly address electronic resonances whose corresponding photon energy lies in the vacuum and deep ultraviolet spectral regions. By harnessing the capabilities of soliton self-compression in novel micro-structured waveguides, we have generated pulses in the deep ultraviolet with energies of hundreds of nanojoules. The delivery of these pulses to an experiment as well as the measurement of their temporal profile pose significant challenges due to the dispersive properties of optical materials in the ultraviolet. We have developed an in-vacuum device for ultrafast pulse characterisation, and by directly coupling the waveguide to vacuum we were able to measure distortion-free pulses with durations below 10 fs at a range of different central wavelengths. Numerical modelling of a scaled-up version of the apparatus shows that the self-compressed driving pulse in the ultraviolet pulse generation process can maintain its shape when delivered directly to vacuum. The single-cycle pulse duration makes it an ideal driver for extreme nonlinear optics and the generation of isolated attosecond pulses in the soft X-ray spectral region.Open Acces

High-energy ultraviolet dispersive-wave emission in compact hollow capillary systems

We demonstrate high-energy resonant dispersive-wave emission in the deep ultraviolet (218 to 375 nm) from optical solitons in short (15 to 34cm) hollow capillary fibres. This down-scaling in length compared to previous results in capillaries is achieved by using small core diameters (100 and 150 $\mu$m) and pumping with 6.3 fs pulses at 800 nm. We generate pulses with energies of 4 to 6 $\mu$J across the deep ultraviolet in a 100 $\mu$m capillary and up to 11 $\mu$J in a 150 $\mu$m capillary. From comparisons to simulations we estimate the ultraviolet pulse to be 2 to 2.5 fs in duration. We also numerically study the influence of pump duration on the bandwidth of the dispersive wave.Comment: 5 pages, 3 figure

High-energy pulse self-compression and ultraviolet generation through soliton dynamics in hollow capillary fibres

Optical soliton dynamics can cause the extreme alteration of the temporal and spectral shape of a propagating light pulse. They occur at up to kilowatt peak powers in glass-core optical fibres and the gigawatt level in gas-filled microstructured hollow-core fibres. Here we demonstrate optical soliton dynamics in large-core hollow capillary fibres. This enables scaling of soliton effects by several orders of magnitude to the multi-mJ energy and terawatt peak power level. We experimentally demonstrate two key soliton effects. First, we observe self-compression to sub-cycle pulses and infer the creation of sub-femtosecond field waveforms - a route to high-power optical attosecond pulse generation. Second, we efficiently generate continuously tunable high-energy (1 to 16 $\mu$J) pulses in the vacuum and deep ultraviolet (110 nm to 400 nm) through resonant dispersive-wave emission.These results promise to be the foundation of a new generation of table-top light sources for ultrafast strong-field physics and advanced spectroscopy