Experimental demonstration of a Displacement noise Free Interferometry scheme for gravitational wave detectors showing displacement noise reduction at low frequencies

This paper reports an experimental demonstration of partial displacement noise free laser interferometry in the gravitational wave detection band. The used detuned Fabry-Perot cavity allows the isolation of the mimicked gravitational wave signal from the displacement noise on the cavities input mirror. By properly combining the reflected and transmitted signals from the cavity a reduction of the displacement noise was achieved. Our results represent the first experimental demonstration of this recently proposed displacement noise free laser interferometry scheme. Overall we show that the rejection ratio of the displacement noise to the gravitational wave signal was improved in the frequency range of 10 Hz to 10 kHz with a typical factor of 60.Comment: 5 pages, 3 figure

External quantum efficiency enhancement by photon recycling with backscatter evasion

The nonunity quantum efficiency (QE) in photodiodes (PD) causes deterioration of signal quality in quantum optical experiments due to photocurrent loss as well as the introduction of vacuum fluctuations into the measurement. In this paper, we report that the external QE enhancement of a PD was demonstrated by recycling the reflected photons. The external QE for an InGaAs PD was increased by 0.01 - 0.06 from 0.86 - 0.92 over a wide range of incident angles. Moreover, we confirmed that this technique does not increase backscattered light when the recycled beam is properly misaligned

An analysis and visualization of the output mode-matching requirements for squeezing in Advanced LIGO and future gravitational wave detectors

The sensitivity of ground-based gravitational wave (GW) detectors will be improved in the future via the injection of frequency-dependent squeezed vacuum. The achievable improvement is ultimately limited by losses of the interferometer electromagnetic field that carries the GW signal. The analysis and reduction of optical loss in the GW signal chain will be critical for optimal squeezed light-enhanced interferometry. In this work we analyze a strategy for reducing output-side losses due to spatial mode mismatch between optical cavities with the use of adaptive optics. Our goal is not to design a detector from the top down, but rather to minimize losses within the current design. Accordingly, we consider actuation on optics already present and one transmissive optic to be added between the signal recycling mirror and the output mode cleaner. The results of our calculation show that adaptive mode-matching with the current Advanced LIGO design is a suitable strategy for loss reduction that provides less than 2% mean output mode-matching loss. The range of actuation required is +47 uD on SR3, +140 mD on OM1 and OM2, +50 mD on the SRM substrate, and -50 mD on the added new transmissive optic. These requirements are within the demonstrated ranges of real actuators in similar or identical configurations to the proposed implementation. We also present a novel technique that graphically illustrates the matching of interferometer modes and allows for a quantitative comparison of different combinations of actuators.Comment: Matches version accepted in PR

Supplement: "Localization and broadband follow-up of the gravitational-wave transient GW150914" (2016, ApJL, 826, L13)

This Supplement provides supporting material for Abbott et al. (2016a). We briefly summarize past electromagnetic (EM) follow-up efforts as well as the organization and policy of the current EM follow-up program. We compare the four probability sky maps produced for the gravitational-wave transient GW150914, and provide additional details of the EM follow-up observations that were performed in the different bands

Experimental demonstration of displacement noise free interferometry

General relativity describes gravity as the curvature of space-time. The theory predicts the existence of gravitational waves (GWs), which can be described as ripples in space-time propagating at the speed of light. So far no direct detection of GWs has been achieved. The sensitivities of the currently leading laser interferometric GW detectors are limited by various noise sources, i.e. seismic, thermal, shot noises etc. Several conceptual studies are underway investigating new techniques that aim to improve sensitivities enough to fulfil the requirements of the next generation of detectors. One of these new techniques under investigation is displacement and frequency noise free interferometry (DFI). This thesis reports on the experimental demonstration of a new method of partial DFI that is effective in the GW detection frequency band. The isolation of a mimicked GW signal from displacement noise of one mirror is demonstrated for a detuned Fabry-Perot cavity. A significant reduction in the displacement noise of the cavity input mirror was achieved by properly combining the reflected and transmitted signals from the cavity. This result represents the first experimental demonstration of this recently proposed DFI scheme, and lays the foundations for future work aimed at implementing DFI schemes in up-coming laser interferometric GW detectors

Soil pollution in a decommissioned shooting range: a preliminary survey of the spatial variability of legacy pollutants

Outdoor shooting ranges provide recreational facilities for millions of people in the world. However, there are many negative effects on the environment and public health arising from this activity. In particular, potential risks are mostly associated with the residential or agricultural use of decommissioned outdoor ranges, where bullets and targets have been deposited during the shooting activity. This is the case of an outdoor shooting range in Campania region (Southern Italy), located in an area of historical and naturalistic value, close to the ancient Etruscan village of Suessola (VII century b.C.). Specifically, the study site is located within an agricultural land declared unsuitable for agricultural and forest-pastoral production by the Italian Ministry of Agricultural, Food and Forestry Resources, due to an extensive long term soil contamination associated with Pb, Sb, PAHs, dioxins, PCBs and C> 12 hydrocarbons. With the purpose of planning a detailed site characterization of the shooting range area, a preliminary environmental survey was carried out by means of field investigations (ultrasonic penetrometry, electromagnetic induction - EMI - and gamma spectroscopy) and geochemical prospecting. Cone index data, obtained by ultrasonic penetrometer measurements, indicated the presence of a very dense, hard and impenetrable to hand hauger layer, recognised as travertine rock, from 25 to more than 55 cm of depth, and dipping northward. Continuous EMI data and gamma spectroscopy (K %, eU ppm, eTh ppm) parameters were acquired in the field in order to identify homogeneous zones in which further geochemical investigations should have been focused. In fact, apparent electrical conductivity (ECa) map, consistently with the gamma ray dose rate distribution map, allowed to highlight three separated singularity areas N-S oriented. XRF analyses, carried out through a portable analyzer on soil samples collected along soil profiles digged from topsoil until the travertine layer, showed a high contamination by Pb (greater than 1000 mg/kg) and Sb (greater than 30 mg/kg) in the first 15 cm of depth, at a distance of approximately 90 m from the shooting lanes. Chemical analyses were also performed on 32 topsoil samples collected on the basis of a regular grid across the study area. Concentrations of 13 PAHs compounds were determined and the highest values were found close to the firing lanes where in soil a huge amount of shooting target fragments are present. The preliminary results showed how the contamination due to the previous activity in the area produced a spatial distribution of contaminats differentiated on the basis of their source material and their role in the shooting process