0000000000022634
AUTHOR
T. Diehl
Triple resonant four-wave mixing: A microwatt continuous-wave laser source in the vacuum ultraviolet region at 120 nm
We present a vacuum ultraviolet laser source by four-wave mixing in mercury vapour based on solid-state laser systems. Maximum powers of 6μW were achieved with an increase of four orders of magnitude in efficiency.
Electrostatically operated micromirrors for a Hadamard transform spectrometer
The paper presents the development of a linear micromirror array which can be used as a switchable entrance mask for a double-array Hadamard transform spectrometer. In addition to the detector array the double-array spectrometer has a linear multi-slit array realised by independently switchable micromirrors at the entrance side. Two different switch positions of the electrostatically operated mirrors allow the reflection of light into or away from the spectrometer. With this arrangement (mirror array, concave grating and array detector) and the use of the Hadamard transform principle it is possible to increase the signal-to-noise ratio and the resolution of the system compared to convention…
A continuous wave 10 W cryogenic fiber amplifier at 1015 nm and frequency quadrupling to 254 nm
A stable, continuous wave, single frequency fiber amplifier system at 1015 nm with 10W output power is presented. It is based on a large mode double clad fiber cooled to liquid nitrogen temperature. The amplified light is frequency quadrupled to 254 nm and used for spectroscopy of the 6^1S - 6^3P transition in mercury.
A semiconductor laser system for the production of antihydrogen
Laser-controlled charge exchange is a promising method for producing cold antihydrogen. Caesium atoms in Rydberg states collide with positrons and create positronium. These positronium atoms then interact with antiprotons, forming antihydrogen. Las er excitation of the caesium atoms is essential to increase the cross section of the charge-exchange collisions. This method was demonstrated in 2004 by the ATRAP collaboration by using an available copper vapour laser. For a second generation of charge-e xchange experiments we have designed a new semiconductor laser system that features several improvements compared to the copper vapour laser. We describe this new laser system and show the resul…
SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study
Abstract Background Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18–49, 50–69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results NNVs were more favourable in su…
Continuous Lyman-alpha generation by four-wave mixing in mercury for laser cooling of antihydrogenThis paper was presented at the International Conference on Precision Physics of Simple Atomic Systems, held at École de Physique, les Houches, France, 30 May – 4 June, 2010.
Cooling antihydrogen atoms is important for future experiments both to test the fundamental CPT symmetry by high resolution laser spectroscopy and also to measure the gravitational acceleration of antimatter. Laser cooling of antihydrogen can be done on the strong 1S–2P transition at the wavelength of Lyman-alpha (121.6 nm). A continuous wave laser at the Lyman-alpha wavelength based on solid-state fundamental lasers is described. By using a two-photon and a near one-photon resonance a scan across the whole phase matching curve of the four-wave mixing process is possible. Furthermore the influence of the beam profile of one fundamental beam on the four-wave mixing process is studied.