7 W mid-infrared supercontinuum generation up to 4.7 µm in an indium-fluoride optical fiber pumped by a high-peak power thulium-doped fiber single-oscillator.

In this letter, a high-power supercontinuum (SC) generation is achieved in an InF3 fiber with a maximum all bands output power of 7 W and spectrum extension up to 4.7 µm. An actively Q-switched mode-locked (QML) Tm3+-doped fiber single-oscillator has been used to pump the fluoride fiber. At the average power level of 15 W, the most energetic QML pulse provided by the fiber laser had an energy of 88 µJ and an estimated peak power of 60 kW. To the best of our knowledge, this is the first experimental demonstration of a Watt-level range supercontinuum generation in an InF3 fiber pumped by a single-oscillator laser system.

Resonantly pumped eye-safe Er3+:YAG SPS-HIP ceramic laser.

We report for the first time laser action in resonantly-pumped transparent polycrystalline Er3+:YAG ceramic developed through a 2-step approach combining spark plasma sintering and HIP post treatment. Microstructural and spectroscopic properties, as well as the laser performance of large scale 0.5at.% Er:YAG transparent polycrystalline ceramic are discussed. A maximum slope efficiency of ∼31% and optical-optical efficiency of 20% was measured.

In-vacuum Faraday isolation remote tuning.

In-vacuum Faraday isolators (FIs) are used in gravitational wave interferometers to prevent the disturbance caused by light reflected back to the input port from the interferometer itself. The efficiency of the optical isolation is becoming more critical with the increase of laser input power. An in-vacuum FI, used in a gravitational wave experiment (Virgo), has a 20 mm clear aperture and is illuminated by an almost 20 W incoming beam, having a diameter of about 5 mm. When going in vacuum at 10(-6) mbar, a degradation of the isolation exceeding 10 dB was observed. A remotely controlled system using a motorized lambda=2 waveplate inserted between the first polarizer and the Faraday rotator has proven its capability to restore the optical isolation to a value close to the one set up in air.

An upper limit on the stochastic gravitational-wave background of cosmological origin.

A stochastic background of gravitational waves is expected to arise from a superposition of a large number of unresolved gravitational-wave sources of astrophysical and cosmological origin. It should carry unique signatures from the earliest epochs in the evolution of the Universe, inaccessible to standard astrophysical observations. Direct measurements of the amplitude of this background are therefore of fundamental importance for understanding the evolution of the Universe when it was younger than one minute. Here we report limits on the amplitude of the stochastic gravitational-wave background using the data from a two-year science run of the Laser Interferometer Gravitational-wave Observatory (LIGO). Our result constrains the energy density of the stochastic gravitational-wave background normalized by the critical energy density of the Universe, in the frequency band around 100 Hz, to be <6.9 x 10(-6) at 95% confidence. The data rule out models of early Universe evolution with relatively large equation-of-state parameter, as well as cosmic (super)string models with relatively small string tension that are favoured in some string theory models. This search for the stochastic background improves on the indirect limits from Big Bang nucleosynthesis and cosmic microwave background at 100 Hz.