Erzeugung und Anwendung geformter Laserpulse mit oktavbreitem Spektrum

Der Traum der "kohärenten Quantenkontrolle", mit Hilfe von Laserlicht chemische Reaktionen zu steuern bzw. quantenmechanische Systeme gezielt in einen gewünschten Endzustand zu überführen, ist durch die rasche Entwicklung im Bereich der Erzeugung ultrakurzer Laserpulse und der Kontrolle ihrer spektralen Phase in vielen Bereichen bereits verwirklicht worden. In dieser Arbeit gelang durch die Kombination eines Laseroszillators mit einem oktavbreiten Spektrum und einem eigens dafür entworfenen hocheffizienten Pulsformer ein entscheidender Schritt zur Kontrolle des zeitlichen Intensitätsverlaufs von Laserpulsen auf einer Skala von wenigen Femtosekunden. Durch den Einsatz des Pulsformers als flexible Dispersionskompensation konnten die bislang kürzesten Lichtpulse direkt aus einem Laser-Oszillator mit einer Dauer von 4,3 fs erzeugt werden. Zusätzlich konnten zahlreiche zeitliche Pulsformen wie Doppel- oder Dreifachpulse mit variablem Abstand demonstriert worden. In einer ersten Anwendung konnten zweifarbige Doppelpulse zur Femtosekunden-Spektroskopie an dem Laserfarbstoff HDITCP eingesetzt und drei Molekül-Schwingungsmoden identifiziert werden. Desweiteren wurden die ultrakurzen Laserpulse zur Bildgebung in der nichtlinearen Optischen Kohärenztomographie eingesetzt und dadurch eine bislang unübertroffene Tiefenauflösung von 1,9 µm erreicht. Diese kann durch den Einsatz geformter Laserpulse in Zukunft weiter gesteigert und die chemische Selektivität der Bilder deutlich erhöht werden

Tracking spectral shapes and temporal dynamics along a femtosecond filament

The spectral evolution of a high-intensity light channel formed by filamentation is investigated in a detailed experimental study. We also track the spatio-temporal dynamics by high-order harmonic generation along the filament. Both the spectral and temporal diagnostics are performed as a function of propagation distance, by extracting the light pulses directly from the hot filament core into vacuum via pinholes that terminate the nonlinear propagation. We compare the measured spectral shapes to simulations and analyze numerically the temporal dynamics inside the filament. © 2011 Optical Society of America

High-order harmonic spectroscopy in an ionized high-density target

We use high-order harmonic spectroscopy to study ionization dynamics in a macroscopic target with tunable density, spanning over six orders of magnitude. In an in situ pump-probe experiment, the target is prepared at different densities with varying degrees of laser-induced ionization. High-order harmonic radiation is generated in the pre-ionized target, and a steepening in the decrease of the harmonic yield is observed for increasing pre-ionization, allowing not only to identify the contributing quantum paths during high-order harmonic generation but also in determining the amount of ionization within the target. The measurements allow probing of ionization dynamics in laser-induced plasma with high spatio-temporal resolution and are specifically of interest for the optimization of the harmonic generation process in high-density targets with number densities of up to 1022 cm−3

Tunable sub-20 fs pulses from a 500 kHz OPCPA with 15 W average power based on an all-ytterbium laser

An optical parametric chirped pulse amplifier fully based on Yb lasers at 500 kHz is described. Passive optical-synchronization is achieved between a fiber laser-pumped white-light and a 515 nm pump produced with a 200 W picosecond Yb:YAG InnoSlab amplifier. An output power up to 19.7 W with long-term stability of 0.3% is demonstrated for wavelength tunable pulses between 680 nm and 900 nm and spectral stability of 0.2%; 16.5 W can be achieved with a bandwidth supporting 5.4 fs pulses. We demonstrate compression of 30 microjoule pulses to sub-20 fs duration with a prism compressor, suitable for high harmonic generation.Comment: 4 pages, 4 figure

Book illustration

Book synopsis: William Blake, poet and artist, is a figure often understood to have 'created his own system'. Combining close readings and detailed analysis of a range of Blake's work, from lyrical songs to later myth, from writing to visual art, this collection of thirty-eight lively and authoritative essays examines what Blake had in common with his contemporaries, the writers who influenced him, and those he influenced in turn. Chapters from an international team of leading scholars also attend to his wider contexts: material, formal, cultural, and historical, to enrich our understanding of, and engagement with, Blake's work. Accessibly written, incisive, and informed by original research, William Blake in Context enables readers to appreciate Blake anew, from both within and outside of his own idiom

Fast-tunable femtosecond visible radiation via sum-frequency generation from a high power NIR NOPO

We report on a high power ultra-broadband, quickly tunable non-collinear parametric oscillator with highly efficient intra-cavity sum-frequency generation. It simultaneously delivers femtosecond pulses in two synchronized output beams: up to 4.9 W tunable from 650 to 1050 nm in the near infrared and up to 1.9 W from 380 to 500 nm in the visible spectral range. The (to our knowledge) novel source is ideally suited for spectroscopy or multi-color imaging. First results of two-color functional microscopy are presented

Improving hand therapy delivery during care transitions in multisystem trauma patients

High-quality hand therapy is critical to maximising functional capacity and optimising overall outcomes following hand injuries. Therapy delivery requires clear communication between surgeons and occupational therapists. At Sunnybrook Health Sciences Centre (SHSC), Canada’s largest tertiary care centre, suboptimal communication is a significant barrier to efficient hand therapy delivery in acute multisystem trauma patients. A baseline audit at SHSC found that 41% of hand therapy orders required clarification and 35% of patients waited over 24 hours before their order was fulfilled. In many cases, communication errors created unacceptably long delays that were suspected by surgeon stakeholders to impede patient outcomes. This highlighted an opportunity for investigation and system improvement.Using process mapping methodology, we outlined standard process involved in patient care and identified barriers to successful communication. We collaborated with key stakeholders to codesign a standardised template for care orders. We aimed to improve order clarity and consistency with the goal of reducing the incidence of clarification and delays.Postimplementation, the percentage of hand therapy orders requiring clarification was decreased to 24%. The number of patients waiting over 24 hours for therapy was also reduced; however, further investigation is required to verify this finding. In addition, essential order components were more consistently and comprehensively included. Next steps of this work include expanding the use of the order template outside of the multisystem trauma population and improving the communication of hand therapy at discharge from hospital