Supercontinuum generation in the vacuum ultraviolet through dispersive-wave and soliton-plasma interaction in noble-gas-filled hollow-core photonic crystal fiber

We report on the generation of a three-octave-wide supercontinuum extending from the vacuum ultraviolet (VUV) to the near-infrared, spanning at least 113 to 1000 nm (i.e., 11 to 1.2 eV), in He-filled hollow-core kagome-style photonic crystal fiber. Numerical simulations confirm that the main mechanism is a novel and previously undiscovered interaction between dispersive-wave emission and plasma-induced blueshifted soliton recompression around the fiber zero dispersion frequency. The VUV part of the supercontinuum, which modeling shows to be coherent and possess a simple phase structure, has sufficient bandwidth to support single-cycle pulses of 500 attosecond duration. We also demonstrate, in the same system, the generation of narrower-band VUV pulses, through dispersive-wave emission, tunable from 120 to 200 nm with efficiencies exceeding 1% and VUV pulse energies in excess of 50 nJ.Comment: 7 pages, 5 figure

Ultrakurze UV Pulse erzeugt durch nichtlineare Licht-Materie Interaktion in gasgefüllten Hohlkernfasern: Erzeugung und Charakterisierung

This work aims to demonstrate that the gas-filled kagome hollow-core photonic crystal fibre (HC-PCF) can be an efficient source of coherent ultraviolet pulses covering the entire spectral range from 100 nm to 350 nm and having a duration as short as 4 fs. By controlling the gas fillings and the pressure along with the pump pulse parameters (such as pulse duration and energy) it is possible to reach the regime where solitons are generated in the fibre. Subsequent soliton self-compression down to subfemtoseconds duration, partial ionization of a gas in the fibre core and interaction between the soliton and the plasma allows generation of dispersive waves tunable across the vacuum ultraviolet spectral region. The efficiency of the source exceeds 1% with the vacuum UV pulse energies in excess of 50 nJ. By choosing the optimal set of parameters, the supercontinuum, spanning at least between 115-1000 nm, was generated. Furthermore this source of dispersive waves in the vacuum UV was shown to be useful in angle resolved photoemission spectroscopy. The full temporal and spectral characterization of ultraviolet pulses is essential for many applications. Therefore a significant part of this thesis consists of the design and realization of transient grating cross-correlation frequency resolved optical gating (TG-XFROG) for the characterization of UV dispersive waves. A dispersive wave centered at 275 nm was measured to have a duration as short as 4 fs, proving its ultrashort nature. TG-XFROG was also shown to be very broadband and sensitive, potentially allowing for the measurements of the full supercontinuum from deep UV to near IR. Finally the possibility to generate dispersive waves in the extreme UV region was demonstrated numerically and the experimental layout allowing such measurements was suggested.Ziel dieser Arbeit ist es zu demonstrieren, dass gasgefüllte Hohlkern photonic crystal fibre (PCF) mit kagome Struktur eine effiziente Quelle ist für kohärente ultraviolette (UV) Pulse im gesamten Spektralbereich von 100 bis 350 nm, mit einer Pulsdauer die bis zu 4 fs kurz ist. Durch Einstellen des Füllgases und dessen Drucks sowie der Parameter der Pumppulse (wie deren Dauer und Energie) ist es möglich, Solitonen in der Faser zu generieren. Die Soliton-Selbstkompression zu Pulsdauern von weniger als einer Femtosekunde, die teilweise Ionisation des Gases im Kern der Faser und die Interaktion der Solitonen mit dem Plasma ermöglichen die Generierung von dispersiven Wellen, die über den Vakuum-UV Spektralbereich durchstimmbar sind. Die Effizienz dieser Quelle liegt bei über einem Prozent und die Pulsenergien im Vakuum-UV betragen mehr als 50 nJ. Durch optimale Wahl der Parameter wurde ein Superkontinuum erzeugt, das mindestens von 115 bis 1000 nm reicht. Darüber hinaus wurde gezeigt, dass diese Quelle von dispersiven Wellen im Vakuum-UV nützlich für winkelaufgelöste Photoemissionsspektroskopie ist. Die komplette zeitliche und spektrale Charakterisierung von UV-Pulsen ist essentiell für viele Anwendungen. Ein beträchtlicher Teil dieser Arbeit besteht daher aus dem Design und der Realisierung eines transient-grating cross-correlation frequency-resolved optical gating (TG-XFROG) Aufbaus zur Charakterisierung der dispersiven Wellen im UV. Die Messung einer dispersiven Welle mit 275 nm Zentralwellenlänge ergab bis zu 4 fs kurze Pulse und bestätigt damit deren ultrakurze Zeitdauer. Es wurde weiterhin gezeigt, dass der TG-XFROG Aufbau sehr breitbandig und sensitiv ist und somit potenziell die Messung des gesamten Superkontinuum-Spektrums vom tiefen UV bis zum Nahinfraroten ermöglicht. Abschließend wurde die Möglichkeit dispersive Wellen im extremen UV Spekiii Zusammenfassung tralbereich zu erzeugen numerisch demonstriert und eine Experimentieranordnung für solche Messungen vorgeschlagen

A Comparative Study of Machine Learning Methods for Predicting Live Weight of Duroc, Landrace, and Yorkshire Pigs

Simple Summary Live weight is an important indicator of livestock productivity and serves as an informative measure for the health, feeding, breeding, and selection of livestock. In this paper, the live weight of pig was estimated using six morphometric measurements, breed, weight at birth, weight at weaning, and age at weaning. In the present paper, we propose a comparative analysis of various machine learning methods using outlier detection, normalisation, hyperparameter optimisation, and stack generalisation to increase the accuracy of the predictions of the live weight of pigs. The StackingRegressor algorithm yielded a prediction quality of the live weight of Duroc, Landrace, and Yorkshire pigs that was higher than that of the state-of-the art algorithms. Live weight is an important indicator of livestock productivity and serves as an informative measure for the health, feeding, breeding, and selection of livestock. In this paper, the live weight of pig was estimated using six morphometric measurements, weight at birth, weight at weaning, and age at weaning. This study utilised a dataset including 340 pigs of the Duroc, Landrace, and Yorkshire breeds. In the present paper, we propose a comparative analysis of various machine learning methods using outlier detection, normalisation, hyperparameter optimisation, and stack generalisation to increase the accuracy of the predictions of the live weight of pigs. The performance of live weight prediction was assessed based on the evaluation criteria: the coefficient of determination, the root-mean-squared error, the mean absolute error, and the mean absolute percentage error. The performance measures in our experiments were also validated through 10-fold cross-validation to provide a robust model for predicting the pig live weight. The StackingRegressor model was found to provide the best results with an MAE of 4.331 and a MAPE of 4.296 on the test dataset

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