Nonlinear pulse compression to sub-two-cycle, 1.3 mJ pulses at 1.9 μm wavelength with 132 W average power.

We report the nonlinear pulse compression of a high-power, thulium-doped fiber laser system using a gas-filled hollow-core fiber. The sub-two cycle source delivers 1.3 mJ pulse energy with 80 GW peak power at a central wavelength of 1.

Continuously tunable high photon flux high harmonic source.

In this work, a continuously tunable extreme ultraviolet source delivering a state-of-the-art photon flux of >10 ph/s/eV spanning from 50 eV to 70 eV is presented. The setup consists of a high-power fiber laser with a subsequent multipass cell followed by a waveguide-based high harmonic generation setup. Spectral tuning over the full line spacing is achieved by slightly adjusting the lasers driving pulse energy, utilizing nonlinear propagation effects and pulse chirping.

Inband-pumped, high-power thulium-doped fiber amplifiers for an ultrafast pulsed operation.

We investigate the influence of the pump wavelength on the high-power amplification of large-mode area, thulium-doped fibers which are suitable for an ultrashort pulsed operation in the 2 µm wavelength region. By pumping a standard, commercially available photonic crystal fiber in an amplifier configuration at 1692 nm, a slope efficiency of 80 % at an average output power of 60 W could be shown. With the help of simulations we investigate the effect of cross-relaxations on the efficiency and the thermal behavior.

Ultrafast Tm-doped fiber laser system delivering 1.65-mJ, sub-100-fs pulses at a 100-kHz repetition rate.

High-energy, ultrafast, short-wavelength infrared laser sources with high average power are important tools for industrial and scientific applications. Through the coherent combination of four ultrafast thulium-doped rod-type fiber amplifiers, we demonstrate a Tm-doped chirped pulse amplification system with a compressed pulse energy of 1.65 mJ and 167 W of average output power at a repetition rate of 101 kHz.

Transverse mode instability and thermal effects in thulium-doped fiber amplifiers under high thermal loads.

We experimentally analyze the average-power-scaling capabilities of ultrafast, thulium-doped fiber amplifiers. It has been theoretically predicted that thulium-doped fiber laser systems, with an emission wavelength around 2 µm, should be able to withstand much higher heat-loads than their Yb-doped counterparts before the onset of transverse mode instability (TMI) is observed. In this work we experimentally verify this theoretical prediction by operating thulium doped fibers at very high heat-load.

Investigation of spatiotemporal output beam profile instabilities from differentially pumped capillaries.

Differentially pumped capillaries, i.e., capillaries operated in a pressure gradient environment, are widely used for nonlinear pulse compression.

Watt-scale super-octave mid-infrared intrapulse difference frequency generation.

The development of high-power, broadband sources of coherent mid-infrared radiation is currently the subject of intense research that is driven by a substantial number of existing and continuously emerging applications in medical diagnostics, spectroscopy, microscopy, and fundamental science. One of the major, long-standing challenges in improving the performance of these applications has been the construction of compact, broadband mid-infrared radiation sources, which unify the properties of high brightness and spatial and temporal coherence. Due to the lack of such radiation sources, several emerging applications can be addressed only with infrared (IR)-beamlines in large-scale synchrotron facilities, which are limited regarding user access and only partially fulfill these properties.

Trends in human immunodeficiency virus diagnoses among men who have sex with men in North America, Western Europe, and Australia, 2000-2014.

Purpose: The aim of the article was to investigate recent trends in human immunodeficiency virus (HIV) diagnosis rates among men who have sex with men (MSM) in high-income countries in North America, Western Europe, and Australia.

Methods: Data on annual rates of HIV diagnoses among MSM aged 15 to 65 years from 2000 to 2014 were collected from 13 high-income countries. Joinpoint regression software was used to empirically determine country-specific trend periods.

Carbon chloride-core fibers for soliton mediated supercontinuum generation.

We report on soliton-fission mediated infrared supercontinuum generation in liquid-core step-index fibers using highly transparent carbon chlorides (CCl, CCl). By developing models for the refractive index dispersions and nonlinear response functions, dispersion engineering and pumping with an ultrafast thulium fiber laser (300 fs) at 1.92 μm, distinct soliton fission and dispersive wave generation was observed, particularly in the case of tetrachloroethylene (CCl).

Hybrid soliton dynamics in liquid-core fibres.

The discovery of optical solitons being understood as temporally and spectrally stationary optical states has enabled numerous innovations among which, most notably, supercontinuum light sources have become widely used in both fundamental and applied sciences. Here, we report on experimental evidence for dynamics of hybrid solitons-a new type of solitary wave, which emerges as a result of a strong non-instantaneous nonlinear response in CS-filled liquid-core optical fibres. Octave-spanning supercontinua in the mid-infrared region are observed when pumping the hybrid waveguide with a 460 fs laser (1.

Decreasing Proportion of Recent Infections among Newly Diagnosed HIV-1 Cases in Switzerland, 2008 to 2013 Based on Line-Immunoassay-Based Algorithms.

Background: HIV surveillance requires monitoring of new HIV diagnoses and differentiation of incident and older infections. In 2008, Switzerland implemented a system for monitoring incident HIV infections based on the results of a line immunoassay (Inno-Lia) mandatorily conducted for HIV confirmation and type differentiation (HIV-1, HIV-2) of all newly diagnosed patients. Based on this system, we assessed the proportion of incident HIV infection among newly diagnosed cases in Switzerland during 2008-2013.

Impact of atmospheric molecular absorption on the temporal and spatial evolution of ultra-short optical pulses.

We present a rigorous study on the impact of atmospheric molecular absorption on the linear propagation of ultrashort pulses in the mid-infrared wavelength region. An ultrafast thulium-based fiber laser was employed to experimentally investigate ultrashort-pulse propagation through the atmosphere in a spectral region containing several strong molecular absorption lines. The atmospheric absorption profile causes a significant degradation of the pulse quality in the time domain as well as a distortion of the transverse beam profile in the spatial domain.

Tm-based fiber-laser system with more than 200 MW peak power.

Tm-based fiber-laser systems are an attractive concept for the development of high-performance laser sources in the spectral region around 2 μm wavelength. Here we present a system delivering a pulse-peak power higher than 200 MW in combination with 24 W average power and 120 μJ pulse energy. Key components enabling this performance level are a Tm-doped large-pitch fiber with a mode-field diameter of 65 μm, highly efficient dielectric gratings, and a Tm-based fiber oscillator operating in the stretched-pulse regime.

152 W average power Tm-doped fiber CPA system.

A high-power thulium (Tm)-doped fiber chirped-pulse amplification system emitting a record compressed average output power of 152 W and 4 MW peak power is demonstrated. This result is enabled by utilizing Tm-doped photonic crystal fibers with mode-field diameters of 35 μm, which mitigate detrimental nonlinearities, exhibit slope efficiencies of more than 50%, and allow for reaching a pump-power-limited average output power of 241 W. The high-compression efficiency has been achieved by using multilayer dielectric gratings with diffraction efficiencies higher than 98%.

High peak-power mid-infrared ZnGeP₂ optical parametric oscillator pumped by a Tm:fiber master oscillator power amplifier system.

We report on the utilization of a novel Tm:fiber laser source for mid-IR ZnGeP2 (ZGP) optical parametric oscillator (OPO) pumping. The pump laser is built in a master oscillator power-amplifier configuration delivering up to 3.36 W of polarized, diffraction limited output power with 7 ns pulse duration and 4 kHz repetition rate.

Simple estimation of incident HIV infection rates in notification cohorts based on window periods of algorithms for evaluation of line-immunoassay result patterns.

Background: Tests for recent infections (TRIs) are important for HIV surveillance. We have shown that a patient's antibody pattern in a confirmatory line immunoassay (Inno-Lia) also yields information on time since infection. We have published algorithms which, with a certain sensitivity and specificity, distinguish between incident (< = 12 months) and older infection.

Amplification of nanosecond pulses to megawatt peak power levels in Tm3+-doped photonic crystal fiber rod.

We report amplification of sub-10-100 ns pulses with repetition rates from 1 to 20 kHz in a rod-type thulium-doped photonic crystal fiber with 80 μm core diameter. The rod is pumped with a 793 nm laser diode and produces the highest peak power at 1 kHz repetition rate with 6.5 ns pulse duration and more than 7 W average output power.

Resurgence of HIV infection among men who have sex with men in Switzerland: mathematical modelling study.

Background: New HIV infections in men who have sex with men (MSM) have increased in Switzerland since 2000 despite combination antiretroviral therapy (cART). The objectives of this mathematical modelling study were: to describe the dynamics of the HIV epidemic in MSM in Switzerland using national data; to explore the effects of hypothetical prevention scenarios; and to conduct a multivariate sensitivity analysis.

Methodology/principal Findings: The model describes HIV transmission, progression and the effects of cART using differential equations.

Diagnostic performance of line-immunoassay based algorithms for incident HIV-1 infection.

Background: Serologic testing algorithms for recent HIV seroconversion (STARHS) provide important information for HIV surveillance. We have previously demonstrated that a patient's antibody reaction pattern in a confirmatory line immunoassay (INNO-LIA™ HIV I/II Score) provides information on the duration of infection, which is unaffected by clinical, immunological and viral variables. In this report we have set out to determine the diagnostic performance of Inno-Lia algorithms for identifying incident infections in patients with known duration of infection and evaluated the algorithms in annual cohorts of HIV notifications.

High specificity of line-immunoassay based algorithms for recent HIV-1 infection independent of viral subtype and stage of disease.

Background: Serologic testing algorithms for recent HIV seroconversion (STARHS) provide important information for HIV surveillance. We have shown that a patient's antibody reaction in a confirmatory line immunoassay (INNO-LIA HIV I/II Score, Innogenetics) provides information on the duration of infection. Here, we sought to further investigate the diagnostic specificity of various Inno-Lia algorithms and to identify factors affecting it.

Assessment of recent HIV-1 infection by a line immunoassay for HIV-1/2 confirmation.

Background: Knowledge of the number of recent HIV infections is important for epidemiologic surveillance. Over the past decade approaches have been developed to estimate this number by testing HIV-seropositive specimens with assays that discriminate the lower concentration and avidity of HIV antibodies in early infection. We have investigated whether this "recency" information can also be gained from an HIV confirmatory assay.

Surveillance systems for sexually transmitted diseases in Switzerland.

Background: In Switzerland (population 7.4 million), 3 different systems contribute to surveillance for sexually transmitted infections.

Goal: The goal of this study was to compare time trends from surveillance systems for chlamydia, gonorrhea, and syphilis.