Abstract
In this paper, we propose a multichannel spectral configuration of the Astronomical Light Optical Hybrid Analysis (ALOHA) instrument dedicated to high-resolution imaging. A frequency ...conversion process is implemented in each arm of an interferometer to transfer the astronomical light to a shorter wavelength domain. Exploiting the spectral selectivity of this non-linear optical process, we propose to use a set of independent pump lasers in order to simultaneously study multiple spectral channels. This principle is experimentally demonstrated with a dual-channel configuration as a proof-of-principle.
In this paper, we report on a novel method to control the coherence behavior in a sum frequency generation interferometer powered by two independent pump lines. At the output of the interferometer, ...the two incoherent fringe patterns must be superimposed to maximize the contrast. The first step consists in canceling the differential group delay. The second one uses the phase control on one pump to synchronize the fringe patterns. This innovative method is experimentally demonstrated with a setup involving a 1544 nm signal and two pump lines around 1064 nm leading to a converted signal around 630 nm. It can be easily extended to a greater number of pump lines.
We report on the implementation of a mid-infrared (MIR) interferometer prototype for furthermore application in the framework of high-resolution imaging in astronomy. This paper demonstrates the ...possibility to extend to the L band our experimental study performed on the up-conversion interferometer in H band. This in-laboratory preliminary experiment allowed us to get the first fringes with the MIR Astronomical Light Optical Hybrid Analysis (ALOHA) @3.39 μm up-conversion interferometer with a bright quasi monochromatic source (HeNe 3.39 μm). A stable contrast greater than 98 per cent has been reached. This opens the possibility to propose an alternative instrument for the demanding domain of high resolution imaging in the MIR domain.
The Astronomical Light Optical Hybrid Analysis project investigates the combined use of a telescope array interferometer and nonlinear optics to propose a new generation of instruments dedicated to ...high-resolution imaging for infrared astronomy. The nonlinear process of optical frequency conversion transfers the astronomical light to a shorter wavelength domain. Here, we report on the first fringes obtained on the sky with the prototype operated at 1.55 μm in the astronomical H band and implemented on the Center for High Angular Resolution Astronomy telescope array. This seminal result allows us to foresee a future extension to the challenging midinfrared spectral domain.
Context. The tip-tilt stabilisation system of the 1.8 m Auxiliary Telescopes of the Very Large Telescope Interferometer was never dimensioned for robust fringe tracking, except when atmospheric ...seeing conditions are excellent. Aims. Increasing the level of wavefront correction at the telescopes is expected to improve the coupling into the single-mode fibres of the instruments, and enable robust fringe tracking even in degraded conditions. Methods. We deployed a new adaptive optics module for interferometry (NAOMI) on the Auxiliary Telescopes. Results. We present its design, performance, and effect on the observations that are carried out with the interferometric instruments.
We report on the implementation of a mid-infrared (MIR) interferometer prototype for furthermore application in the framework of high-resolution imaging in astronomy. This paper demonstrates the ...possibility to extend to the L band our experimental study performed on the up-conversion interferometer in H band. This in-laboratory preliminary experiment allowed us to get the first fringes with the MIR Astronomical Light Optical Hybrid Analysis (ALOHA) @3.39 μm up-conversion interferometer with a bright quasi monochromatic source (HeNe 3.39 μm). A stable contrast greater than 98 per cent has been reached. This opens the possibility to propose an alternative instrument for the demanding domain of high resolution imaging in the MIR domain.
This paper gives an overview of the Astronomical Light Optical Hybrid Analysis (ALOHA) project dedicated to investigate a new method for high resolution imaging in mid infrared astronomy. This ...proposal aims to use a non-linear frequency conversion process to shift the thermal infrared radiation to a shorter wavelength domain compatible with proven technology such as guided optics and detectors. After a description of the principle, we summarise the evolution of our study from the high flux seminal experiments to the latest results in the photon counting regime.
Background. In the sub-Saharan African, region of the world with a fast growing aging population and where the use of herbal products is very common, there is a paucity of data on medication ...consumption patterns among elderly people. The objective of this study was to assess the prevalence of polypharmacy and its associated factors among community-dwelling elderly in Lomé, Togo, in 2017. Methods. A cross-sectional study was conducted from March to June 2017 in Lomé, Togo among people aged 60 years and older. The Respondent Driven Sampling method was used to recruit participants. Data on socio-demographic characteristics and medication consumption patterns, including the use of medicinal plants and dietary supplements, were collected using a standardized questionnaire during a face-to-face interview at participants’ home. Descriptive and binary logistic regression analyses were performed. Results. A total of 370 participants with median age 65 years, (IQR: 62–71) were enrolled in the study. Almost three elderly in five (57.6%) were multimorbid (had two or more chronic diseases). Conventional drugs (78.4%), medicinal plants (14.3%) and other dietary supplements (9.5%) were used by participants. The prevalence of polypharmacy was 22.7% (95% CI: 18.5–27.3%). Concurrent use of conventional drugs and medicinal plants or other dietary supplements was observed among 17.0% of participants and 67.3% reported self-medication. Multimorbidity (aOR = 4.55; 95% CI: 2.42–8.54) and female sex (aOR = 1.86; 95% CI: 1.00–3.47) were associated with polypharmacy. Conclusion. One elderly in five uses five or more medications in Togo. Further studies are needed to assess drug-drug interactions and herb-drug interactions among this population.
This paper gives an overview of the Astronomical Light Optical Hybrid Analysis (ALOHA) project dedicated to investigate a new method for high resolution imaging in mid infrared astronomy. This ...proposal aims to use a non-linear frequency conversion process to shift the thermal infrared radiation to a shorter wavelength domain compatible with proven technology such as guided optics and detectors. After a description of the principle, we summarise the evolution of our study from the high flux seminal experiments to the latest results in the photon counting regime.
In the frame of sum frequency generation of a broadband infrared source, we aim to enlarge the converted bandwidth by using a pump frequency comb while keeping a high conversion efficiency. The ...nonlinear effects are simultaneously induced in the same nonlinear medium. In this paper, we investigate the spectral filtering effect on the temporal coherence behavior with a Mach-Zehnder interferometer using two pump lines. We show that joined effects of quasi-phase matching and spectral sampling lead to an original coherence behavior.
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