Domains of holomorphy for irreducible unitary representations of simple Lie groups

We classify the domains of holomorphy of all Harish-Chandra modules of irreducible unitary representations of simple non-compact Lie groups.Comment: revised version, to appear in Invent. math., 14 page

Precision Measurement of Optical Pulsation using a Cherenkov Telescope

During 2003, a camera designed to measure the optical pulsations of pulsars was installed on a telescope of the H.E.S.S. array. The array is designed for gamma-ray astronomy in the ~100 GeV - 100 TeV energy regime. The aims of this exercise were two-fold: to prove the pulsar timing capabilities of H.E.S.S. on all relevant time-scales, and to explore the possibility of performing sensitive optical pulsar measurements using the ~100 m^2 mirror of a Cherenkov telescope. Measurements of the Crab pulsar with this instrument demonstrate an order of magnitude sensitivity improvement over previous attempts using Cherenkov telescopes. Here we describe the design and performance of the system and discuss design considerations for future instruments of this type.Comment: Accepted for publication in Astroparticle Physics, 14 pages, 7 figure

Ecological light measurement in forests using the light degradation effect in hydrogenated amorphous silicon (a-Si:H)

A method is presented for ecological light measurements in forests based on the principle that light produces electrically active defects within the mobility gap in semiconductors from hydrogenated amorphous silicon (a-Si:H), causing measurable changes in the photoconductivity of the semiconductor. A comparison with measurements of the relative illuminance in mixed montane forests led to reasonable results. Suitability for field experiments, drawbacks and possible improvements of this low-cost integrating measurement method, which requires no external energy source, are discussed at length.Mesure de la lumière en forêts au moyen de la dégradation par la lumière du silicium amorphe hydrogéné (a-Si:H). Une méthode est présentée pour la mesure de la lumière en forêts, basée sur l'utilisation de semiconducteurs à base de silicium amorphe hydrogéné (a-Si:H). Une comparaison avec la mesure de l'éclairement relatif dans des forêts mélangées de montagne conduit à des résultats raisonnables. Les défauts et les améliorations possibles de cette méthode peu coûteuse pour des mesures intégrées, ne nécessitant pas de source extérieure d'énergie, sont discutés en détail par les auteurs

STRUCTURAL, COMPOSITIONAL, AND OPTICAL PROPERTIES OF ULTRATHIN Si/Ge SUPERLATTICES

Strained-layer superlattices (SLS) composed of a sequence of ultrathin Si and Ge layers are grown on Ge(110) buffer layers by MBE. Crystalline quality, relaxation of asymmetrically SLS, and interdiffusion are studied in situ by LEED and AES. New optical transitions in the range of 0.7 to 0.8 eV are observed with photoluminescence experiments

Stability optimized, 4-mJ and 1.2-ps pulses from a Ho:YLF regenerative amplifier

Optimization of gain depletion in Ho:YLF regenerative amplifiers resulted in highly stable pulses with fluctuations of 0.35%. Integration of an intra-cavity-etalon decreased the pulse duration to 1.2 ps, while having pulse energies of 4 mJ

Intracavity gain shaping in millijoule-level, high gain Ho:YLF regenerative amplifiers

We demonstrate intracavity gain shaping inside a 2 μm Ho:YLF regenerative amplifier with a spectral bandwidth of 2.9 nm broadened to 5.4 nm, corresponding to Fourier-limited pulses of 1 ps duration. The intracavity gain shaping is achieved by using a simple etalon, which acts as a frequency-selective filter. The output of the regenerative amplifier is amplified by a single-pass amplifier, and we achieve total energy of 2.2 mJ and pulse duration of 2.4 ps at 1 kHz with pulse fluctuations <1%. The amplifier chain is seeded by a home-built mode-locked holmium-doped fiber oscillator

High energetic and highly stable pulses from a Ho:YLF regenerative amplifier

We present results from our Ho:YLF regenerative amplifier (RA) producing up to 6.9 mJ at a repetition rate of 1 kHz and up to 12.9 mJ at a repetition rate of 10 Hz. At 1 kHz, we observe strongly bifurcating pulses, starting with certain round trip number, but the measurements identify a highly stable operation point that lies “hidden” beyond the instability region. This operation point allows the extraction of highly stable and high energetic output pulses. Suppression of bifurcation in our system is presented for repetition rates below 750 Hz and Ho:YLF crystal holder temperatures of 2.5 °C. We furthermore present a stability optimization routine for our Ho:YLF RA that was operated close to gain depletion at a repetition rate of 100 Hz. By varying the Ho:YLF crystal holder temperature the gain depletion level could be fine adjusted, resulting in a highly stable RA system with measured pulse fluctuations of only 0.35 %