Real-time observation of interfering crystal electrons in high-harmonic generation

Accelerating and colliding particles has been a key strategy to explore the texture of matter. Strong lightwaves can control and recollide electronic wavepackets, generating high-harmonic (HH) radiation which encodes the structure and dynamics of atoms and molecules and lays the foundations of attosecond science. The recent discovery of HH generation in bulk solids combines the idea of ultrafast acceleration with complex condensed matter systems and sparks hope for compact solid-state attosecond sources and electronics at optical frequencies. Yet the underlying quantum motion has not been observable in real time. Here, we study HH generation in a bulk solid directly in the time-domain, revealing a new quality of strong-field excitations in the crystal. Unlike established atomic sources, our solid emits HH radiation as a sequence of subcycle bursts which coincide temporally with the field crests of one polarity of the driving terahertz waveform. We show that these features hallmark a novel non-perturbative quantum interference involving electrons from multiple valence bands. The results identify key mechanisms for future solid-state attosecond sources and next-generation lightwave electronics. The new quantum interference justifies the hope for all-optical bandstructure reconstruction and lays the foundation for possible quantum logic operations at optical clock rates

Symmetry-controlled temporal structure of high-harmonic carrier fields from a bulk crystal

High-harmonic (HH) generation in crystalline solids1, 2, 3, 4, 5, 6 marks an exciting development, with potential applications in high-efficiency attosecond sources7, all-optical bandstructure reconstruction8, 9 and quasiparticle collisions10, 11. Although the spectral1, 2, 3, 4 and temporal shape5 of the HH intensity has been described microscopically1, 2, 3, 4, 5, 6, 12, the properties of the underlying HH carrier wave have remained elusive. Here, we analyse the train of HH waveforms generated in a crystalline solid by consecutive half cycles of the same driving pulse. Extending the concept of frequency combs13, 14, 15 to optical clock rates, we show how the polarization and carrier-envelope phase (CEP) of HH pulses can be controlled by the crystal symmetry. For certain crystal directions, we can separate two orthogonally polarized HH combs mutually offset by the driving frequency to form a comb of even and odd harmonic orders. The corresponding CEP of successive pulses is constant or offset by π, depending on the polarization. In the context of a quantum description of solids, we identify novel capabilities for polarization- and phase-shaping of HH waveforms that cannot be accessed with gaseous sources

An Overview of Three Promising Mechanical, Optical, and Biochemical Engineering Approaches to Improve Selective Photothermolysis of Refractory Port Wine Stains

During the last three decades, several laser systems, ancillary technologies, and treatment modalities have been developed for the treatment of port wine stains (PWSs). However, approximately half of the PWS patient population responds suboptimally to laser treatment. Consequently, novel treatment modalities and therapeutic techniques/strategies are required to improve PWS treatment efficacy. This overview therefore focuses on three distinct experimental approaches for the optimization of PWS laser treatment. The approaches are addressed from the perspective of mechanical engineering (the use of local hypobaric pressure to induce vasodilation in the laser-irradiated dermal microcirculation), optical engineering (laser-speckle imaging of post-treatment flow in laser-treated PWS skin), and biochemical engineering (light- and heat-activatable liposomal drug delivery systems to enhance the extent of post-irradiation vascular occlusion)

Munich Method Of Micrographic Surgery For Basal Cell Carcinomas: 5-Year Recurrence Rates With Life-Table Analysis

The aim of this study was to find the recurrence rates of basal cell carcinomas treated with micrographic surgery in the Department of Dermatology, University of Regensburg. From 1992 to 1997, 261 basal cell carcinomas (178 primary and 83 recurrent) have been treated. The mean duration of follow-up was 5 years (range 1-9). Data were analysed by life-table analysis. Eleven basal cell carcinomas (6 primary and 5 recurrent) recurred. The 5-year recurrence rates were 3.3% for primary and 7.3% for recurrent basal cell carcinomas. Our results are comparable with previously published data from Europe but seem higher than those reported in the USA. Use of different statistical methods to report the recurrence rates mainly accounts for the discrepancy among studies. For a better comparison among studies on recurrence rates, a standard statistical method should be used, and we support the idea that life-table analysis provides the best approximation of the true recurrence rates.WoSScopu

Correlations Between Light Penetration into Skin and the Therapeutic Outcome Following Laser Therapy of Port-wine Stains

For several years the flashlamp-pumped pulsed dye laser (FPDL) has been the favoured method for the treatment of port-wine stains (PWS). The therapeutic outcome of FPDL laser therapy depends on the anatomical location of the PWS and is mainly attributed to morphological parameters such as size and depth of the PWS blood vessels. The aim of this study was to show a correlation between the therapeutic outcome following FPDL therapy and the optical properties of the skin overlying the PWS vessels. For this purpose the therapeutic outcome following FPDL treatment (585 nm; 0.45 ms) of 884 PWS situated on different body sites was evaluated by judging the grade of fading of PWS colour. On the other hand the light penetration into 123 skin samples (thickness 0.10–1.35 mm) was determined between 450 nm and 1030 nm and compared with the PWS laser therapy outcome for equal locations by statistical analysis. PWS on the neck, trunk, arms or legs yielded a higher mean grade of fading as compared to PWS on the head. Within the face, a wide range of fading was evident. The light penetration into skin increased linearly with increasing wavelength and locationdependent differences were found. The attenuation coefficient was 22.8-5.3 mm$^{-1}$ at 585 nm. No significant or strong correlation was observed between the therapeutic outcome of PWS laser therapy and the light penetration into skin. However, a correlation was obvious by plotting the respective profile plots. Therefore, among other effects, in particular morphological parameters of PWS vessels, the optical properties of the skin contribute to a small extent to the clinical outcome of PWS laser therapy