Artykuły w czasopismach: „Mid-IR sources”

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Perger, M., J. Moultaka, A. Eckart, T. Viehmann, R. Schödel i K. Muzic. "Compact mid-IR sources east of Galactic Center source IRS5". Astronomy & Astrophysics 478, nr 1 (20.11.2007): 127–35. http://dx.doi.org/10.1051/0004-6361:20078449.

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Mountrichas, G., I. Georgantopoulos, A. Ruiz i G. Kampylis. "Obscuration properties of mid-IR-selected AGN". Monthly Notices of the Royal Astronomical Society 491, nr 2 (4.11.2019): 1727–35. http://dx.doi.org/10.1093/mnras/stz3076.

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ABSTRACT The goal of this work is to study the obscuration properties of mid-infrared (mid-IR)-selected active galactic nuclei (AGN). For that purpose, we use Wide-field Infrared Survey Explorer (WISE) sources in the Stripe 82–XMM area to identify mid-IR AGN candidates, applying the Assef et al. criteria. Stripe 82 has optical photometry ≈2 times deeper than any single-epoch Sloan Digital Sky Survey (SDSS) region. XMM–Newton observations cover ∼26 deg2. Applying the aforementioned criteria, 1946 IR AGN are selected. ${\sim} 78{{\, \rm per\, cent}}$ have SDSS detection, while 1/3 of them are detected in X-rays, at a flux limit of $\rm {\sim} 5 \times 10^{-15}\, erg\, s^{-1}\, cm^{-2}$. Our final sample consists of 507 IR AGN with X-ray detection and optical spectra. Applying a $r-W2 > 6$ colour criterion, we find that the fraction of optically red AGN drop from 43 per cent for those sources with SDSS detection to $23{{\, \rm per\, cent}}$ for sources that also have X-ray detection. X-ray spectral fitting reveals 40 (${\sim} 8{{\, \rm per\, cent}}$) X-ray absorbed AGN ($N_\mathrm{ H} > 10^{22}\,{\rm cm}^{-2}$). Among the X-ray unabsorbed AGN, there are 70 red systems. To further investigate the absorption of these sources, we construct spectral energy distributions (SEDs) for the total IR AGN sample. SED fitting reveals that ${\sim} 20{{\, \rm per\, cent}}$ of the optically red sources have such colours because the galaxy emission is a primary component in the optical part of the SED, even though the AGN emission is not absorbed at these wavelengths. SED fitting also confirms that $12{{\, \rm per\, cent}}$ of the X-ray unabsorbed IR AGN are optically obscured.

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Sanghera, Jas S., L. Brandon Shaw i Ishwar D. Aggarwal. "Chalcogenide Glass-Fiber-Based Mid-IR Sources and Applications". IEEE Journal of Selected Topics in Quantum Electronics 15, nr 1 (styczeń 2009): 114–19. http://dx.doi.org/10.1109/jstqe.2008.2010245.

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Weidmann, Damien, Chad B. Roller, Clive Oppenheimer, Alan Fried i Frank K. Tittel. "Carbon isotopomers measurement using mid-IR tunable laser sources". Isotopes in Environmental and Health Studies 41, nr 4 (grudzień 2005): 293–302. http://dx.doi.org/10.1080/10256010500384325.

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Gonzalez-Solares, Eduardo A., Nicholas A. Walton, Anita M. S. Richards i Jonathan A. Tedds. "Near-IR properties of Spitzer sources". Proceedings of the International Astronomical Union 2, nr 14 (sierpień 2006): 611. http://dx.doi.org/10.1017/s1743921307012094.

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We present an analysis of the near-IR properties of galaxies and quasars detected in the mid-IR by the Spitzer Space Telescope. Using optical photometry from the Wide Field Survey and near-IR fluxes from the First Data Release of the UKIDSS (Dye et al. 2006) survey we carry out a preliminary characterization of the surface density of different samples of galaxies and their clustering properties.

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Lerch, Ph, P. Dumas, T. Schilcher, A. Nadji, A. Luedeke, N. Hubert, L. Cassinari i in. "Assessing noise sources at synchrotron infrared ports". Journal of Synchrotron Radiation 19, nr 1 (25.11.2011): 1–9. http://dx.doi.org/10.1107/s0909049511041884.

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Today, the vast majority of electron storage rings delivering synchrotron radiation for general user operation offer a dedicated infrared port. There is growing interest expressed by various scientific communities to exploit the mid-IR emission in microspectroscopy, as well as the far infrared (also called THz) range for spectroscopy. Compared with a thermal (laboratory-based source), IR synchrotron radiation sources offer enhanced brilliance of about two to three orders of magnitude in the mid-IR energy range, and enhanced flux and brilliance in the far-IR energy range. Synchrotron radiation also has a unique combination of a broad wavelength band together with a well defined time structure. Thermal sources (globar, mercury filament) have excellent stability. Because the sampling rate of a typical IR Fourier-transform spectroscopy experiment is in the kHz range (depending on the bandwidth of the detector), instabilities of various origins present in synchrotron radiation sources play a crucial role. Noise recordings at two different IR ports located at the Swiss Light Source and SOLEIL (France), under conditions relevant to real experiments, are discussed. The lowest electron beam fluctuations detectable in IR spectra have been quantified and are shown to be much smaller than what is routinely recorded by beam-position monitors.

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Persi, Paolo, Mauricio Tapia i Anna Rosa Marenzi. "Mid-IR images of methanol masers and ultracompact HII regions". Proceedings of the International Astronomical Union 2, S237 (sierpień 2006): 462. http://dx.doi.org/10.1017/s1743921307002505.

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Methanol masers and UCHII regions trace massive star formation sites. We have undertaken a mid-IR survey of 17 regions containing methanol masers and UCHIIs in order to locate the young stellar sources associated with them. The images were obtained from 8.7 to 18.8 μm with the mid-IR camera CID (Salas et al. 2003) on the 2.1m telescope of the Observatorio Astronomico Nacional at San Pedro Martir (Baja California, Mexico). The images were taken with a scale 0.55″/pix and the mean PSF was 1.5-2.0″(FWHM) close to the diffraction limit. We report as an example in Fig. 1 (left panel) our 18.8μm contours of IRAS 06061+2151 superimposed to the 2MASS Ks image. A young cluster of at least 4 sources has been found centered on the IRAS source (Anandarao et al. 2004). We have found two mid-IR sources coinciding with the source #2 and #4 of Anandarao et al. (2004). The source #4 is at the center of two H2 knots and a high velocity molecular outflow. The mid-IR emission from #2 is extended and coincides with the UCHII and MSX source. The methanol maser is approximately 10″ south of the source #2. The SEDs of both sources are illustrated in Fig. 1 (right panel). The IR spectral indices of source #2 and #4 are α(IR)=1.9 and 2.2 respectively.

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Mescia, L., F. Smektala i F. Prudenzano. "New Trends in Amplifiers and Sources via Chalcogenide Photonic Crystal Fibers". International Journal of Optics 2012 (2012): 1–8. http://dx.doi.org/10.1155/2012/575818.

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Rare-earth-doped chalcogenide glass fiber lasers and amplifiers have great applicative potential in many fields since they are key elements in the near and medium-infrared (mid-IR) wavelength range. In this paper, a review, even if not exhaustive, on amplification and lasing obtained by employing rare-earth-doped chalcogenide photonic crystal fibers is reported. Materials, devices, and feasible applications in the mid-IR are briefly mentioned.

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Zorin, Ivan, Jakob Kilgus, Kristina Duswald, Bernhard Lendl, Bettina Heise i Markus Brandstetter. "Sensitivity-Enhanced Fourier Transform Mid-Infrared Spectroscopy Using a Supercontinuum Laser Source". Applied Spectroscopy 74, nr 4 (25.02.2020): 485–93. http://dx.doi.org/10.1177/0003702819893364.

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Fourier transform infrared (FT-IR) spectrometers have been the dominant technology in the field of mid-infrared (mid-IR) spectroscopy for decades. Supercontinuum laser sources operating in the mid-IR spectral region now offer the potential to enrich the field of FT-IR spectroscopy due to their distinctive properties, such as high-brightness, broadband spectral coverage and enhanced stability. In our contribution, we introduce this advanced light source as a replacement for conventional thermal emitters. Furthermore, an approach to efficient coupling of pulsed mid-IR supercontinuum sources to FT-IR spectrometers is proposed and considered in detail. The experimental part is devoted to pulse-to-pulse energy fluctuations of the applied supercontinuum laser, performance of the system, as well as the noise and long-term stability. Comparative measurements performed with a conventional FT-IR instrument equipped with a thermal emitter illustrate that similar noise levels can be achieved with the supercontinuum-based system. The analytical performance of the supercontinuum-based FT-IR spectrometer was tested for a concentration series of aqueous formaldehyde solutions in a liquid flow cell (500 µm path length) and compared with the conventional FT-IR (130 µm path length). The results show a four-times-enhanced detection limit due to the extended path length enabled by the high brightness of the laser. In conclusion, FT-IR spectrometers equipped with novel broadband mid-IR supercontinuum lasers could outperform traditional systems providing superior performance, e.g., interaction path lengths formerly unattainable, while maintaining low noise levels known from highly stable thermal emitters.

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Koptev, Maksim Yu, Alexander E. Zaprialov, Alexey F. Kosolapov, Alexander N. Denisov, Maria S. Muravyeva, Sergey L. Semjonov, Sergey V. Muravyev i Arkady V. Kim. "Visible to Mid-IR Supercontinuum Generation in Cascaded PCF-Germanate Fiber Using Femtosecond Yb-Fiber Pump". Fibers 11, nr 9 (24.08.2023): 72. http://dx.doi.org/10.3390/fib11090072.

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Broadband supercontinuum (SC) fiber sources covering the mid-IR range have many significant applications, largely due to their compactness, reliability, and ease of use. However, most of the existing SC fiber sources cannot boast of either high reliability or a wide bandwidth. Thus, supercontinuum sources based on silica fibers are robust, but are not capable of generating SC in the mid-IR range. Sources based on soft glasses (tellurite, chalcogenide, etc.) generate broadband SC in the mid-IR range but are not used commercially, due to the poor mechanical and chemical characteristics of such fibers. In this work, we propose a new approach consisting of cascade generation of a supercontinuum sequentially in a silica photonic crystal fiber (PCF) and a germanate fiber. Using a standard ytterbium chirped-pulse amplification (CPA) laser system for pumping, we have demonstrated a supercontinuum in the range of 450–2950 nm in PCF and germanate fiber firmly connected by a standard fusion splicing technique. Further optimization of the cascade pump will make it possible to create a compact and reliable all-fiber SC source from the visible to mid-IR range.

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Hegenbarth, R., A. Steinmann, S. Mastel, S. Amarie, A. J. Huber, R. Hillenbrand, S. Y. Sarkisov i H. Giessen. "High-power femtosecond mid-IR sources for s-SNOM applications". Journal of Optics 16, nr 9 (1.09.2014): 094003. http://dx.doi.org/10.1088/2040-8978/16/9/094003.

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GEORGANTOPOULOS, I. "RECENT DEVELOPMENTS IN THE SEARCH FOR COMPTON-THICK AGN". International Journal of Modern Physics: Conference Series 23 (styczeń 2013): 1–10. http://dx.doi.org/10.1142/s2010194513010994.

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I present a review of X-ray and mid-IR surveys for Compton-thick Active Galactic Nuclei (AGN). These are the most highly obscured sources having hydrogen column densities > 1.5 × 1024 cm-2. Key surveys in the local Universe are presented including the high energy SWIFT/BAT and INTEGRAL surveys, mid-IR and also optical surveys. Recently, deep X-ray surveys with Chandra and XMM-Newton have produced a number of candidate Compton-thick AGN at higher redshift primarily in the Chandra Deep Field South region. In addition, mid-IR surveys with Spitzer have helped to develop novel complementary techniques for the selection of Compton-thick AGN. The mid-IR techniques used to identify Compton-thick AGN include: a) 24 μm excess sources relative to their optical emission b) Spitzer spectroscopy for the detection of high optical depth Si 9.7μm absorption features c) low X-ray to 6μm luminosity ratio.

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Skinner, C. J., G. Hawkins, M. M. Meixner, J. G. Jernigan i J. F. Arens. "10μM Images of AGB Stars & Supergiants". Symposium - International Astronomical Union 155 (1993): 320. http://dx.doi.org/10.1017/s0074180900171086.

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We present mid-IR and far-IR images of a variety of AGB stars and red supergiants. The mid-IR images were all taken with the Berkeley/Livermore mid-IR array camera, which employs a 10 × 64 pixel Hughes photoconductor. All the images reported here were taken using a 10% bandpass CVF, at various wavelengths in the 10μm atmospheric window. These were supplemented by IRAS images, some constructed from survey scans, others made as Additional Observations during the pointed phase of the IRAS mission. We have so far observed 11 such sources with our mid-IR camera, and report here that only two of them (R Aql and V Hya) appear to be unresolved.

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Jaturaphagorn, Pawaphat, Papichaya Chaisakul, Nattaporn Chattham i Pichet Limsuwan. "Investigation on optical integration between LED Mid-IR light sources and Si-based waveguides for sensing applications". Journal of Physics: Conference Series 2145, nr 1 (1.12.2021): 012056. http://dx.doi.org/10.1088/1742-6596/2145/1/012056.

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Abstract Research on mid-IR silicon-based waveguides has recently received strong interest. Particularly, this paper focuses on one of the critical issues in micron-scale photonic integrated circuits, which is to efficiently couple a mid-IR LED (light emitting diode) light source to an external micron-scale waveguide. The optical coupling scheme is crucial for the exploitation of LED light sources in waveguide-based spectroscopic sensing applications. This paper reports optical coupling scheme between an LED mid-IR light source and a silicon rich silicon nitride (SiN) waveguide that could enable the use of LED-based light sources. Finally, the detection limit of the investigated device for carbon dioxide gas detection is calculated.

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Pushkin, Andrey, Ekaterina Migal, Dina Suleimanova, Evgeniy Mareev i Fedor Potemkin. "High-Power Solid-State Near- and Mid-IR Ultrafast Laser Sources for Strong-Field Science". Photonics 9, nr 2 (2.02.2022): 90. http://dx.doi.org/10.3390/photonics9020090.

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This review highlights the development of ultrafast sources in the near- and middle-IR range, developed in the laboratory of Nonlinear Optics and Superstrong Laser Fields at Lomonosov Moscow State University. The design of laser systems is based on a powerful ultrafast Cr:Forsterite system as a front-end and the subsequent nonlinear conversion of radiation into the mid-IR, THz, and UV spectral range. Various schemes of optical parametric amplifiers based on oxide and non-oxide crystals pumped with Cr:Forsterite laser can receive pulses in the range of 4–6 µm with gigawatt peak power. Alternative sources of mid-IR ultrashort laser pulses at a relatively high (MHz) repetition rate are also proposed as difference frequency generators and as a femtosecond mode-locked oscillator based on an Fe:ZnSe crystal. Iron ion-doped chalcogenides (Fe:ZnSe and Fe:CdSe) are shown to be effective gain media for broadband high-peak power mid-IR pulses in this spectral range. The developed sources pave the way for advanced research in strong-field science.

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Way, Brandyn, Ravinder K. Jain i Mani Hossein-Zadeh. "High-Q microresonators for mid-IR light sources and molecular sensors". Optics Letters 37, nr 21 (18.10.2012): 4389. http://dx.doi.org/10.1364/ol.37.004389.

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Cancio, P., S. Bartalini, S. Borri, I. Galli, G. Gagliardi, G. Giusfredi, P. Maddaloni, P. Malara, D. Mazzotti i P. De Natale. "Frequency-comb-referenced mid-IR sources for next-generation environmental sensors". Applied Physics B 102, nr 2 (18.09.2010): 255–69. http://dx.doi.org/10.1007/s00340-010-4216-2.

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Sarajedini, Vicki L. "Using AGN Variability Surveys to explore the AGN-Galaxy Connection". Proceedings of the International Astronomical Union 9, S304 (październik 2013): 385–90. http://dx.doi.org/10.1017/s1743921314004372.

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AbstractVariability is a successful technique used to identify active galactic nuclei in both ground and space-based galaxy surveys. Optical variability surveys using HST have uncovered a number of AGN in deep extragalactic fields extending to z ~ 3 and probing intrinsically faint sources. Mid-IR variability surveys using Spitzer have identified a significant number of AGN and are particularly sensitive to obscured sources. Many variability-detected AGN are not strong X-ray sources or lack the characteristic colors of AGN and would thus be unidentified using other selection techniques. In this conference proceedings, I discuss the nature of the variable sources and their host galaxies identified in deep extragalactic optical and mid-IR surveys.

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Conti, Peter S., Jeonghee Rho, James Furness i Paul A. Crowther. "UCHII Regions and Newly Born O-type Stars". Proceedings of the International Astronomical Union 3, S250 (grudzień 2007): 285–92. http://dx.doi.org/10.1017/s1743921308020607.

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AbstractWe have obtainedSpitzerIRAC and MIPS mid-IR images of a sample of 43 radio selected UCHII region sources to ascertain (a) whether the newly born O stars within are found with other stars in their birthplaces and (b) the nature of the surroundings. 37 of the sources appear to be in small clusters, and 33 are found in connection with other hot star formation activity. Thus, for the most part, O stars are not born in isolation. Here we give examples of the mid-IR images of the various types of UCHII regions.

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Inami, Hanae, Jason Surace, Lee Armus, Aaron S. Evans, Kirsten L. Larson, Loreto Barcos-Munoz, Sabrina Stierwalt i in. "GOALS-JWST: Unveiling Dusty Compact Sources in the Merging Galaxy IIZw096". Astrophysical Journal Letters 940, nr 1 (1.11.2022): L6. http://dx.doi.org/10.3847/2041-8213/ac9389.

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Abstract We have used the Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST) to obtain the first spatially resolved, mid-infrared images of IIZw096, a merging luminous infrared galaxy (LIRG) at z = 0.036. Previous observations with the Spitzer Space Telescope suggested that the vast majority of the total IR luminosity (L IR) of the system originated from a small region outside of the two merging nuclei. New observations with JWST/MIRI now allow an accurate measurement of the location and luminosity density of the source that is responsible for the bulk of the IR emission. We estimate that 40%–70% of the IR bolometric luminosity, or 3–5 × 1011 L ⊙, arises from a source no larger than 175 pc in radius, suggesting a luminosity density of at least 3–5 × 1012 L ⊙ kpc−2. In addition, we detect 11 other star-forming sources, five of which were previously unknown. The MIRI F1500W/F560W colors of most of these sources, including the source responsible for the bulk of the far-IR emission, are much redder than the nuclei of local LIRGs. These observations reveal the power of JWST to disentangle the complex regions at the hearts of merging, dusty galaxies.

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Lin, Hongtao, Zhengqian Luo, Tian Gu, Lionel C. Kimerling, Kazumi Wada, Anu Agarwal i Juejun Hu. "Mid-infrared integrated photonics on silicon: a perspective". Nanophotonics 7, nr 2 (4.12.2017): 393–420. http://dx.doi.org/10.1515/nanoph-2017-0085.

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AbstractThe emergence of silicon photonics over the past two decades has established silicon as a preferred substrate platform for photonic integration. While most silicon-based photonic components have so far been realized in the near-infrared (near-IR) telecommunication bands, the mid-infrared (mid-IR, 2–20-μm wavelength) band presents a significant growth opportunity for integrated photonics. In this review, we offer our perspective on the burgeoning field of mid-IR integrated photonics on silicon. A comprehensive survey on the state-of-the-art of key photonic devices such as waveguides, light sources, modulators, and detectors is presented. Furthermore, on-chip spectroscopic chemical sensing is quantitatively analyzed as an example of mid-IR photonic system integration based on these basic building blocks, and the constituent component choices are discussed and contrasted in the context of system performance and integration technologies.

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Vorontsov, K. V., S. G. Garanin, N. A. Egorov, N. G. Zakharov, R. A. Zorin, V. B. Kolomeets, V. I. Lazarenko i in. "Nonlinear frequency conversion of a Ho :YAG laser beam". Quantum Electronics 52, nr 3 (1.03.2022): 262–68. http://dx.doi.org/10.1070/qel18007.

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Abstract We report the results of experiments on frequency conversion of a Ho : YAG laser beam (wavelength λ ∼ 2.1 μm) into the near-, mid-, and far-IR regions, aimed at expanding the spectral composition of compact multispectral sources of coherent radiation. The experimentally found laser conversion efficiency into the second harmonic reaches 32 % and 54 % in the cw and repetitively pulsed regimes, respectively. The parametric conversion efficiency into the mid-IR range (λ = 3.5 – 5.0 μm) reaches 55 %, while for the far-IR range (λ = 8 – 8.2 μm) it turns out to be 10.5 %.

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Stallard, Brian R. "Near-IR versus Mid-IR: Separability of Three Classes of Organic Compounds". Applied Spectroscopy 51, nr 5 (maj 1997): 625–30. http://dx.doi.org/10.1366/0003702971941025.

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Recently there has been a surge of interest in spectroscopic sensors operating in the near-IR, although it is recognized that the mid-IR contains more spectral information. The general question addressed in this paper is, How much specificity is lost in choosing the near-IR over the mid-IR for sensor applications? The example considered is the separability among three classes of organic compounds: alkanes, alcohols, and ketones/aldehydes. We use spectra from two sources: the Hummel polymer library (mid-IR) and the library of Buback and Vögele (near-IR). This is the first paper on class separability to make use of this new near-IR library, available in digital form only since July 1995. Five spectral regions are considered: region 5, 10,500 to 6300 cm−1; region 4, 7200 to 5200 cm−1; region 3, 5500 to 3800 cm−1; region 2, 3900 to 2500 cm−1; and region 1, 2500 to 500 cm−1. Class separability is explored both qualitatively and quantitatively with the use of principal component scatter plots, linear discriminant analysis, Bhattacharyya distances, and other methods. We find that the separability is greatest in region 1 and least in region 2, with the three near-IR regions being intermediate. Furthermore, we find that, in the near-IR, there is sufficient class separability to ensure that organic compounds of one class can be determined in the midst of interference from the other classes.

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Singh, S. P., V. Mishra, P. K. Datta i Shailendra K. Varshney. "Dispersion Engineered Capillary-Assisted Chalcogenide Optical Fiber Based Mid-IR Parametric Sources". Journal of Lightwave Technology 33, nr 1 (1.01.2015): 55–61. http://dx.doi.org/10.1109/jlt.2014.2371471.

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Iani, Edoardo, Karina I. Caputi, Pierluigi Rinaldi i Vasily I. Kokorev. "A First Look into the Nature of JWST/MIRI 7.7 μm Sources from SMACS 0723". Astrophysical Journal Letters 940, nr 1 (1.11.2022): L24. http://dx.doi.org/10.3847/2041-8213/aca014.

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Abstract Until now, our knowledge of the extragalactic universe at mid-infrared (mid-IR) wavelengths (>5 μm) was limited to rare active galactic nuclei and the brightest normal galaxies up to z ∼ 3. The advent of JWST with its Mid-Infrared Instrument (MIRI) will revolutionize the ability of the mid-IR regime as a key wavelength domain to probe the high-z universe. In this work we present a first study of JWST MIRI 7.7 μm sources selected with >3σ significance from the lensing cluster field SMACS J0723.3-7327. We model their spectral energy distribution (SED) fitting with 13 JWST and Hubble Space Telescope broad bands, in order to obtain photometric redshifts and derived physical parameters for all these sources. We find that this 7.7 μm galaxy sample is mainly composed of normal galaxies up to z = 4 and has a tail of about 2% of sources at higher redshifts to z ≈ 9–10. The vast majority of our galaxies have [3.6]–[7.7] < 0 colors and very few of them need high dust extinction values (A V = 3–6 mag) for their SED fitting. The resulting lensing-corrected stellar masses span the range 107–1011 M ⊙. Overall, our results clearly show that the first MIRI 7.7 μm observations of deep fields are already useful to probe the high-redshift universe and suggest that the deeper 7.7 μm observations to be available very soon will open up, for the first time, the epoch of reionization at mid-IR wavelengths.

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Peña-Herazo, H. A., F. Massaro, V. Chavushyan, N. Masetti, A. Paggi i A. Capetti. "Turin-SyCAT: A multifrequency catalog of Seyfert galaxies". Astronomy & Astrophysics 659 (marzec 2022): A32. http://dx.doi.org/10.1051/0004-6361/202038752.

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Aims. We present the first release of Turin-SyCAT, a multifrequency catalog of Seyfert galaxies. Methods. We selected Seyfert galaxies considering criteria based on radio, infrared, and optical properties and starting from sources belonging to hard X-ray catalogs and surveys. We visually inspected optical spectra available for all selected sources. We adopted homogeneous and stringent criteria in the source selection aiming at reducing the possible contamination from other source classes. Results. Our final catalog includes 351 Seyfert galaxies distinguished in 233 type 1 and 118 type 2. Type 1 Seyfert galaxies appear to have mid-IR colors similar to blazars, but are distinguished from them by their radio-loudness. Additionally, Seyfert 2 galaxies have mid-IR colors more similar to quasars than BL Lac objects. As expected from their spectral properties, type 1 and 2 Seyfert galaxies show a clear distinction when using the u − r color. Finally, we found a tight correlation between the mid-IR fluxes at both 12 and 22 μm (i.e., F12 and F22, respectively) and hard X-ray fluxes between 15 and 150 keV. Both Seyfert types appear to follow the same trend and share similar values of the ratios of F12 and F22 to FHX in agreement with expectations of the AGN unification scenario. Conclusions. As future perspectives, the Turin-SyCAT will then be used to search for heavily obscured Seyfert galaxies among unidentified hard X-ray sources, given the correlation between mid-IR and hard X-rays, and to investigate their large-scale environments.

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Kirkpatrick, Allison, Guang Yang, Aurélien Le Bail, Greg Troiani, Eric F. Bell, Nikko J. Cleri, David Elbaz i in. "CEERS Key Paper. VII. JWST/MIRI Reveals a Faint Population of Galaxies at Cosmic Noon Unseen by Spitzer". Astrophysical Journal Letters 959, nr 1 (1.12.2023): L7. http://dx.doi.org/10.3847/2041-8213/ad0b14.

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Abstract The Cosmic Evolution Early Release Science program observed the Extended Groth Strip (EGS) with the Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST) in 2022. In this paper, we discuss the four MIRI pointings that observed with longer-wavelength filters, including F770W, F1000W, F1280W, F1500W, F1800W, and F2100W. We compare the MIRI galaxies with the Spitzer/MIPS 24 μm population in the EGS field. We find that MIRI can observe an order of magnitude deeper than MIPS in significantly shorter integration times, attributable to JWST's much larger aperture and MIRI’s improved sensitivity. MIRI is exceptionally good at finding faint (L IR < 1010 L ⊙) galaxies at z ∼ 1–2. We find that a significant portion of MIRI galaxies are “mid-IR weak”—they have strong near-IR emission and relatively weaker mid-IR emission, and most of the star formation is unobscured. We present new IR templates that capture how the mid-to-near-IR emission changes with increasing infrared luminosity. We present two color–color diagrams to separate mid-IR weak galaxies and active galactic nuclei (AGN) from dusty star-forming galaxies and find that these color diagrams are most effective when used in conjunction with each other. We present the first number counts of 10 μm sources and find that there are ≲10 IR AGN per MIRI pointing, possibly due to the difficulty of distinguishing AGN from intrinsically mid-IR weak galaxies (due to low metallicities or dust content). We conclude that MIRI is most effective at observing moderate-luminosity (L IR = 109–1010 L ⊙) galaxies at z = 1–2, and that photometry alone is not effective at identifying AGN within this faint population.

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Stern, Daniel. "Multi-Wavelength AGN from Ground and Space, from Far-IR to High-Energy". Proceedings of the International Astronomical Union 9, S304 (październik 2013): 187. http://dx.doi.org/10.1017/s174392131400372x.

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AbstractI will discuss multi-wavelength AGN studies, with a focus on mid-IR and radio selected obscured AGN. Obscured AGN, which are robustly identified across the full sky by WISE, are the dominant AGN population. I will discuss several aspects of the mid-IR obscured AGN population, ranging from detailed studies of extreme sources, the so-called WISE ultraluminous ‘hot dust-obscured galaxy’ or ‘hot DOG’ sample, as well as more general studies comparing obscured and unobscured AGN identified in wide-area surveys.

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Marton, G., L. V. Tóth, L. G. Balázs, S. Zahorecz, Z. Bagoly, I. Horváth, I. I. Rácz i A. Nagy. "A selection of AKARI FIS BSC extragalactic objects". Proceedings of the International Astronomical Union 11, S319 (sierpień 2015): 101. http://dx.doi.org/10.1017/s1743921315010297.

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AbstractThe point sources in the Bright Source Catalogue (BSC) of the AKARI Far–Infrared Surveyor (FIS) were classified based on their far–IR and mid–IR fluxes and colours using Quadratic Discriminant Analysis method (QDA) and Support Vector Machines (SVM). The reliability of our results show that we can successfully separate galactic and extragalactic AKARI point sources in the multidimensional space of fluxes and colours. However, differentiating among the extragalactic sub–types needs further information.

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ISHII, Nobuhisa, Keisuke KANESHIMA, Peiyu XIA,, Nariyuki SAITO, Teruto KANAI i Jiro ITATANI. "Polarization Analysis of High Harmonic Generation in Solids Using Intense Mid-IR Sources". Review of Laser Engineering 48, nr 4 (2020): 168. http://dx.doi.org/10.2184/lsj.48.4_168.

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MANDAL, KRISHNA C., SUNG H. KANG, MICHAEL CHOI i R. DAVID RAUH. "RARE-EARTH DOPED POTASSIUM LEAD BROMIDE MID-IR LASER SOURCES FOR STANDOFF DETECTION". International Journal of High Speed Electronics and Systems 18, nr 03 (wrzesień 2008): 735–45. http://dx.doi.org/10.1142/s0129156408005709.

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The single crystal growth of KPb 2 Br 5 by vertical Bridgman technique using in-house processed zone refined PbBr 2 and KBr with rare-earth terbium doping has been studied. The grown moisture resistant crystals (1.5 cm diameter and 10 cm length) have shown high promise for low phonon energy room temperature solid-state laser applications in the longer side of mid-IR (4-15 µm) due to their high storage lifetimes, wide tunability, and excellent optical quality. The processed crystals are highly transparent ( T = ≥80%) in the 0.4-25 µm spectral region. Repeated melting-freezing cycles during differential scanning calorimetry (DSC) experiments did not reveal any appreciable variation in the melting point or phase transitions, which is indicative of their excellent thermal stability. The emission spectra pumped with a 2 µm source show broadband emissions with peak wavelength of 3 µ m (7 F 4→ 7 F6), 5µ m (7 F 5→ 7 F 6) and 7.9µ m (7 F 4→ 7 F 5). The KPb 2 Br 5: Tb laser crystals will be highly useful for standoff detection of incoming chemical and biological threats using unique infrared absorption signatures.

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32

Kundys, Dmytro, Francesco Graffitti, Richard A. McCracken, Alessandro Fedrizzi i Bohdan Kundys. "Numerical Study of Reconfigurable Mid‐IR Single Photon Sources Based on Functional Ferroelectrics". Advanced Quantum Technologies 3, nr 3 (29.01.2020): 1900092. http://dx.doi.org/10.1002/qute.201900092.

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Thakkar, Pooja, Clément Fleury, Gerald Stocker, Florian Dubois, Thang Duy Dao, Reyhaneh Jannesari, Parviz Saeidi i in. "Coupled Strip-Array Waveguides for Integrated Mid-IR Gas Sensing". Photonics 10, nr 1 (4.01.2023): 55. http://dx.doi.org/10.3390/photonics10010055.

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Non-dispersive infrared (NDIR) absorption spectroscopy is a widespread approach to gas sensing due to its selectivity and conceptual simplicity. One of the main challenges towards the development of fully integrated NDIR sensors is the design and fabrication of microstructures, typically waveguides, that can combine high sensitivity with the ease of integrability of other sensor elements (sources, filters, detectors). Here, we investigate theoretically and experimentally a class of coupled strip-array (CSA) waveguides realized on a SiO2/Si3N4 platform with mass semiconductor fabrication processes. We demonstrate that this class of waveguides shows comparable sensitivity for a wide range of presented geometries, making it a very promising platform for satisfying multiple sensor and fabrication requirements without loss of performance.

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34

Ramos-Larios, G., M. A. Guerrero, H. Mata, X. Fang, A. Nigoche-Netro, J. A. Toalá i G. Rubio. "Spitzer IRS spectroscopy of planetary nebulae". Proceedings of the International Astronomical Union 12, S323 (październik 2016): 335–36. http://dx.doi.org/10.1017/s1743921317000898.

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AbstractWe present Spitzer Space Telescope archival mid-infrared (mid-IR) spectroscopy of a sample of eleven planetary nebulae (PNe). The observations, acquired with the Spitzer Infrared Spectrograph (IRS), cover the spectral range 5.2-14.5 μm that includes the H2 0-0 S(2) to S(7) rotational emission lines. This wavelength coverage has allowed us to derive the Boltzmann distribution and calculate the H2 rotational excitation temperature (Tex). The derived excitation temperatures have consistent values ≃ 900 ±70 K for different sources despite their different structural components. We also report the detection of mid-IR ionic lines of [Ar iii], [S iv], and [Ne ii] in most objects, and polycyclic aromatic hydrocarbon (PAH) features in a few cases.

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35

Tsibidis, George D., i Emmanuel Stratakis. "Ionization dynamics and damage conditions in fused silica irradiated with mid-infrared femtosecond pulses". Applied Physics Letters 122, nr 4 (23.01.2023): 043501. http://dx.doi.org/10.1063/5.0130934.

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The employment of ultrashort laser sources at the mid-infrared (mid-IR) spectral region for dielectrics is expected to open innovative routes for laser patterning and a wealth of exciting applications in optics and photonics. To elucidate the material response to irradiation with mid-IR laser sources, a consistent analysis of the interaction of long wavelength femtosecond pulses with dielectric materials is presented. The influence of the pulse duration is particularly emphasized in specifying the laser parameters for which photoionization and impact ionization are important. Simulation results using pulses at 2.2, 3.2, and 5 μm are conducted to illustrate optimum conditions for the onset of damage on the solid that is related to the occurrence of the optical breakdown. The results predict that the damage threshold scales as ∼[Formula: see text] ([Formula: see text]) at all laser wavelengths. Given the significant effect of the induced excitation level on excitation of surface plasmons (SPs), which account for the formation of laser-induced periodic structures oriented perpendicular to the laser polarization, a correlation of the produced electron densities with SPs and the threshold of SP excitation (∼[Formula: see text], [Formula: see text]) are also discussed in this as yet unexplored spectral region. The results are expected to guide development of an innovative approach to surface patterning using strong mid-IR pulses for advanced applications.

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36

Bailleul, Damien, Esteban Serrano, David Le Coq, Catherine Boussard-Plédel, Frédéric Désévédavy, Frédéric Smektala i Bertrand Kibler. "Mid-infrared supercontinuum source and evanescent wave spectroscopy based on multiple tapered sections of a singleoptical chalcogenide glass rod". EPJ Web of Conferences 287 (2023): 10010. http://dx.doi.org/10.1051/epjconf/202328710010.

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Mid-infrared supercontinuum sources are particularly important for identifying and characterizing molecules and materials through spectroscopy, thus enabling key applications. We here demonstrate the possibility of combining both mid-IR supercontinuum generation and evanescent wave spectroscopy in a single chalcogenide fiber device by means of heat-and-draw processes to manage linear and nonlinear wave-guiding properties.

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López, Fernando M., Carlos Guillermo Giménez de Castro, Cristina H. Mandrini, Paulo J. A. Simões, Germán D. Cristiani, Dale E. Gary, Carlos Francile i Pascal Démoulin. "A solar flare driven by thermal conduction observed in mid-infrared". Astronomy & Astrophysics 657 (styczeń 2022): A51. http://dx.doi.org/10.1051/0004-6361/202141967.

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Context. The mid-infrared (mid-IR) range has been mostly unexplored for the investigation of solar flares. It is only recently that new mid-IR flare observations have begun opening a new window into the response and evolution of the solar chromosphere. These new observations have been mostly performed by the AR30T and BR30T telescopes that are operating in Argentina and Brazil, respectively. Aims. We present the analysis of SOL2019-05-15T19:24, a GOES class C2.0 solar flare observed at 30 THz (10 μm) by the ground-based telescope AR30T. Our aim is to characterize the evolution of the flaring atmosphere and the energy transport mechanism in the context of mid-IR emission. Methods. We performed a multi-wavelength analysis of the event by complementing the mid-IR data with diverse ground- and space-based data from the Solar Dynamics Observatory (SDO), the H-α Solar Telescope for Argentina, and the Expanded Owens Valley Solar Array (EOVSA). Our study includes the analysis of the magnetic field evolution of the flaring region and of the development of the flare. Results. The mid-IR images from AR30T show two bright and compact flare sources that are spatially associated with the flare kernels observed in ultraviolet (UV) by SDO. We confirm that the temporal association between mid-IR and UV fluxes previously reported for strong flares is also observed for this small flare. The EOVSA microwave data revealed flare spectra consistent with thermal free-free emission, which lead us to dismiss the existence of a significant number of non-thermal electrons. We thus consider thermal conduction as the primary mechanism responsible for energy transport. Our estimates for the thermal conduction energy and total radiated energy fall within the same order of magnitude, reinforcing our conclusions.

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Rivera, Nicholas, Gilles Rosolen, John D. Joannopoulos, Ido Kaminer i Marin Soljačić. "Making two-photon processes dominate one-photon processes using mid-IR phonon polaritons". Proceedings of the National Academy of Sciences 114, nr 52 (12.12.2017): 13607–12. http://dx.doi.org/10.1073/pnas.1713538114.

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Phonon polaritons are guided hybrid modes of photons and optical phonons that can propagate on the surface of a polar dielectric. In this work, we show that the precise combination of confinement and bandwidth offered by phonon polaritons allows for the ability to create highly efficient sources of polariton pairs in the mid-IR/terahertz frequency ranges. Specifically, these polar dielectrics can cause emitters to preferentially decay by the emission of pairs of phonon polaritons, instead of the previously dominant single-photon emission. We show that such two-photon emission processes can occur on nanosecond time scales and can be nearly 2 orders of magnitude faster than competing single-photon transitions, as opposed to being as much as 8–10 orders of magnitude slower in free space. These results are robust to the choice of polar dielectric, allowing potentially versatile implementation in a host of materials such as hexagonal boron nitride, silicon carbide, and others. Our results suggest a design strategy for quantum light sources in the mid-IR/terahertz: ones that prefer to emit a relatively broad spectrum of photon pairs, potentially allowing for new sources of both single and multiple photons.

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Pushkin, Andrey, i Fedor Potemkin. "Refining the Performance of mid-IR CPA Laser Systems Based on Fe-Doped Chalcogenides for Nonlinear Photonics". Photonics 10, nr 12 (14.12.2023): 1375. http://dx.doi.org/10.3390/photonics10121375.

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The chirped pulse amplification (CPA) systems based on transition-metal-ion-doped chalcogenide crystals are promising powerful ultrafast laser sources providing access to sub-TW laser pulses in the mid-IR region, which are highly relevant for essential scientific and technological tasks, including high-field physics and attosecond science. The only way to obtain high-peak power few-cycle pulses is through efficient laser amplification, maintaining the gain bandwidth ultrabroad. In this paper, we report on the approaches for mid-IR broadband laser pulse energy scaling and the broadening of the gain bandwidth of iron-doped chalcogenide crystals. The multi-pass chirped pulse amplification in the Fe:ZnSe crystal with 100 mJ level nanosecond optical pumping provided more than 10 mJ of output energy at 4.6 μm. The broadband amplification in the Fe:ZnS crystal in the vicinity of 3.7 μm supports a gain band of more than 300 nm (FWHM). Spectral synthesis combining Fe:ZnSe and Fe:CdSe gain media allows the increase in the gain band (~500 nm (FWHM)) compared to using a single active element, thus opening the route to direct few-cycle laser pulse generation in the prospective mid-IR spectral range. The features of the nonlinear response of carbon nanotubes in the mid-IR range are investigated, including photoinduced absorption under 4.6 μm excitation. The study intends to expand the capabilities and improve the output characteristics of high-power mid-IR laser systems.

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Pierściński, Kamil, Dorota Pierścińska, Grzegorz Sobczak, Aleksandr Kuźmicz, Krzysztof Chmielewski, Katarzyna Krajewska i Piotr Gutowski. "Monolithic, Optically Coupled, Multi-Section Mid-IR Quantum Cascade Lasers". Photonics 8, nr 12 (16.12.2021): 583. http://dx.doi.org/10.3390/photonics8120583.

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Mid-infrared (mid-IR λ ≈ 3–12 μm), single-mode-emission Quantum Cascade Lasers (QCLs) are of significant interest for a wide range of applications, especially as the laser sources are chosen for laser absorption spectroscopy. In this work, we present the design, fabrication and characterization of multi-section, coupled-cavity, mid-IR quantum cascade lasers. The purpose of this work is to propose a design modification for a coupled-cavity device, yielding a single-mode emission with a longer range of continuous tuning during the pulse, in contrast to a 2-section device. This effect was obtained and demonstrated in the work. The proposed design of a 3-section coupled-cavity QCL allows for a single-mode emission with 35 dB side-mode suppression ratio. Additionally, the time-resolved spectra of the wavelength shift during pulse operation, show a continuous tuning of ~3 cm−1 during the 2 μs pulse. The devices were fabricated in a slightly modified, standard laser process using dry etching.

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41

Takagi, Toshinobu, Hideo Matsuhara, Takehiko Wada i Youichi Ohyama. "Photometric studies of PAH emission from distant infrared galaxies". Proceedings of the International Astronomical Union 7, S284 (wrzesień 2011): 456–59. http://dx.doi.org/10.1017/s1743921312009611.

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AbstractUsing extensive mid-IR datasets from AKARI, i.e. 9 band photometry covering the wavelength range from 2 μm to 24 μm and the unbiased spectroscopic survey for sources with Sν (9μm)>0.3 mJy, we investigated the PAHs emission features in distant starburst galaxies. PAH-selected galaxies, selected with an extremely red mid-IR colour due to PAHs, are found to have a peculiar rest-frame 11-to-8 μm flux ratio, which is systematically smaller than nearby starburst/AGN spectral templates. This may indicate a systematic difference in the physical condition of the ISM between nearby and distant starburst galaxies.

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42

Kim, Seong Jin, Nagisa Oi, Tomotsugu Goto, Hiroyuki Ikeda, Simon C.-C. Ho, Hyunjin Shim, Yoshiki Toba i in. "Identification of AKARI infrared sources by the Deep HSC Optical Survey: construction of a new band-merged catalogue in the North Ecliptic Pole Wide field". Monthly Notices of the Royal Astronomical Society 500, nr 3 (4.12.2020): 4078–94. http://dx.doi.org/10.1093/mnras/staa3359.

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ABSTRACT The North Ecliptic Pole field is a natural deep-field location for many satellite observations. It has been targeted many times since it was surveyed by the AKARI space telescope with its unique wavelength coverage from the near- to mid-infrared (mid-IR). Many follow-up observations have been carried out, making this field one of the most frequently observed areas with a variety of facilities, accumulating abundant panchromatic data from the X-ray to the radio wavelength range. Recently, a deep optical survey with the Hyper Suprime-Cam (HSC) at the Subaru telescope covered the NEP-Wide (NEPW) field, which enabled us to identify faint sources in the near- and mid-IR bands, and to improve the photometric redshift (photo-z) estimation. In this work, we present newly identified AKARI sources by the HSC survey, along with multiband photometry for 91 861 AKARI sources observed over the NEPW field. We release a new band-merged catalogue combining various photometric data from the GALEX UV to submillimetre (sub-mm) bands (e.g. Herschel/SPIRE, JCMT/SCUBA-2). About ∼20 000 AKARI sources are newly matched to the HSC data, most of which seem to be faint galaxies in the near- to mid-infrared AKARI bands. This catalogue is motivating a variety of current research, and will be increasingly useful as recently launched (eROSITA/ART-XC) and future space missions (such as JWST, Euclid, and SPHEREx) plan to take deep observations in the NEP field.

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Marris-Morini, Delphine, Vladyslav Vakarin, Joan Manel Ramirez, Qiankun Liu, Andrea Ballabio, Jacopo Frigerio, Miguel Montesinos i in. "Germanium-based integrated photonics from near- to mid-infrared applications". Nanophotonics 7, nr 11 (26.09.2018): 1781–93. http://dx.doi.org/10.1515/nanoph-2018-0113.

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AbstractGermanium (Ge) has played a key role in silicon photonics as an enabling material for datacom applications. Indeed, the unique properties of Ge have been leveraged to develop high performance integrated photodectors, which are now mature devices. Ge is also very useful for the achievement of compact modulators and monolithically integrated laser sources on silicon. Interestingly, research efforts in these domains also put forward the current revolution of mid-IR photonics. Ge and Ge-based alloys also present strong advantages for mid-infrared photonic platform such as the extension of the transparency window for these materials, which can operate at wavelengths beyond 8 μm. Different platforms have been proposed to take benefit from the broad transparency of Ge up to 15 μm, and the main passive building blocks are now being developed. In this review, we will present the most relevant Ge-based platforms reported so far that have led to the demonstration of several passive and active building blocks for mid-IR photonics. Seminal works on mid-IR optical sensing using integrated platforms will also be reviewed.

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Kostyukova, Nadezhda, Evgenii Erushin, Andrey Boyko, Galina Shevyrdyaeva i Dmitry Badikov. "Barium Chalcogenide Crystals: A Review". Photonics 11, nr 3 (21.03.2024): 281. http://dx.doi.org/10.3390/photonics11030281.

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In recent decades, new nonlinear optical materials have been actively developed to create coherent tunable light sources in the mid-infrared (mid-IR) part of the spectrum used in a variety of scientific fields. In the present review, the main attention is focused on barium chalcogenide crystals, including their linear and nonlinear optical properties, laser-induced damage threshold (LIDT), and frequency down-conversion.

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Csanaková, Bianka, Ondřej Novák, Lukáš Roškot, Jiří Mužík, Martin Cimrman, Jaroslav Huynh, Martin Smrž, Helena Jelínková i Tomáš Mocek. "Double-pass optical parametric generator pumped by Yb thin-disk laser for efficient 1.4–2.9 µm mid-IR radiation generation". Laser Physics 33, nr 2 (30.01.2023): 025005. http://dx.doi.org/10.1088/1555-6611/acb353.

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Abstract Many different fields benefit from the usage of light sources emitting in the mid-infrared wavelength range (2–10 µm). A rising need for precise and fast sources in the mid infrared (mid-IR) is reflected in the development of a high-power, picosecond mid-IR source capable of generation at high repetition rates. In this work, we present the optimization of an optical parametric generator, pumped by a 3 W portion of total power of the Yb:YAG thin-disk laser (1.3 ps, 90 kHz, 90 W) by comparing a single-pass and double-pass arrangement output parameters in terms of output power dependences on input power, efficiency, beam profiles, stability, and spectra. The output tunability of both arrangements spanned from 1459 nm to 2891 nm, with the upper limit being influenced by the limited transmission of the dichroic components used in the setup above 2700 nm. It was shown that the double-pass arrangement increases the output power, from 17 mW in the single-pass arrangement to 193 mW in the double-pass arrangement at 1459 nm, resulting in over ten-fold output power increase.

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46

Kolker, D. B., I. V. Sherstov, A. A. Boyko, B. N. Nyushkov, E. Y. Erushin, N. Y. Kostyukova, A. I. Akhmathanov, A. Y. Kiryakova i A. V. Pavluck. "Tunable mid-infrared laser sources for trace-gas analysis". Journal of Physics: Conference Series 2067, nr 1 (1.11.2021): 012013. http://dx.doi.org/10.1088/1742-6596/2067/1/012013.

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Abstract We demonstrate advanced experimental approaches to photoacoustic gas detection with tunable mid-infrared (mid-IR) laser sources of different types. A gas analyzer for registration of various gas components based on a tunable narrow-linewidth optical parametric oscillator (OPO) was designed and investigated. Using this OPO, the possibility of measuring the trace concentration (∼2÷3 ppm) of methane (CH4) in air was experimentally shown. The gas detection capability was enhanced by introducing injection seeding into the OPO. Another gas analyzer was based on a quantum cascade laser (tunable within the range ∼7.6 ÷7.7 μm) and a resonant differential photoacoustic detector. Detection of the ultra-low concentration (∼0.3 ppm) of methane in air was achieved (the standard dispersion was (1σ) ≍ (10–11) ppb with an integration time of 10 s). We compare the presented approaches and outline their further development.

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47

Liu Yang, 刘洋, 曹前 Cao Qian, 刁新财 Diao Xincai, 魏志义 Wei Zhiyi i 常国庆 Chang Guoqing. "超快光纤激光驱动的长波中红外飞秒脉冲光源（特邀）". Infrared and Laser Engineering 50, nr 8 (2021): 20210368. http://dx.doi.org/10.3788/irla20210368.

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Kim, Soocheol, Soyoung Park i Kangbok Lee. "Method for Aerosol Particle and Gas Analyses based on Dual-channel Mid-infrared Sensor". International Journal of Fire Science and Engineering 36, nr 1 (31.03.2022): 1–6. http://dx.doi.org/10.7731/kifse.3d1404d5.

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Although researchers are actively investigating methods to improve fire detector performance, few studies have investigated fire detectors that detect the type of fire. Fire type detection serves a key role in quickly extinguishing fires and preventing their spread. We present a non-dispersive infrared (NDIR)-based dual-channel mid-infrared (mid-IR) method that can detect and classify aerosol particles and gases. 4.2 μm and 4.7 μm mid-IR light emitting diodes (LEDs) light sources with strong absorption for CO2 and CO are employed. and, and the mid-IR LEDs are modulated with 900 Hz and 1,000 Hz, respectively to increase the signal-to-noise ratio and reduce interference between the light sources. The modulated lights pass through the lenses and sample, and are acquired by a photodetector. The transmittances of the 4.2 μm and 4.7 μm lights are measured to detect the aerosol particles and gases, and the aerosol particles and gases are classified via hierarchical clustering using the measured transmittances and the ratio between the measured transmittances. Various aerosol particles and gases are detected by measuring the transmittance, and the aerosol particles and gases are classified by calculating the distance between clusters. Spectral transmittances analysis of different wavelength bands will enable the detection of various aerosol particles and gases, and further improve the classification accuracy. Furthermore, this method can be applied to fire detection to develop a highly useful technique that can detect and classify fire smoke and rapidly detect the type of fire.

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Esparza-Arredondo, D., O. Gonzalez-Martín, D. Dultzin, J. Masegosa, C. Ramos-Almeida, I. García-Bernete, J. Fritz i N. Osorio-Clavijo. "The dust-gas AGN torus as constrained from X-ray and mid-infrared observations". Astronomy & Astrophysics 651 (lipiec 2021): A91. http://dx.doi.org/10.1051/0004-6361/202040043.

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Context. In recent decades, several multiwavelength studies have been dedicated to exploring the properties of the obscuring material in active galactic nuclei (AGN). Various models have been developed to describe the structure and distribution of this material and constrain its physical and geometrical parameters through spectral fitting techniques. However, questions around the way in which torus mid-infrared (mid-IR) and X-ray emission are related remain unanswered. Aims. In this work, we aim to study whether the dust continuum at mid-IR and gas reflection at X-rays have the same distribution in a sample of AGN. Methods. We carefully selected a sample of 36 nearby AGN with NuSTAR and Spitzer spectra available that satisfy the following criteria: (1) the AGN component dominates the mid-IR spectra (i.e., the stellar and interstellar medium components contribute less than 50% to the spectrum), and (2) the reflection component contributes significantly to the X-ray spectrum. Furthermore, we discarded the sources whose reflection component could be produced by ionized material in the disk. We derived the properties of the nuclear dust and gas through a spectral fitting, using models developed for mid-IR and X-ray wavelengths assuming smooth and clumpy distributions for this structure. Results. We find that a combination of smooth and clumpy distributions of gas and dust, respectively, is preferred for ∼80% of sources with good spectral fits according to the Akaike criterion. However, considering extra information about each individual source, such as the absorption variability, we find that ∼50% of our sources are best described by a clumpy distribution of both dust and gas. The remaining ∼50% of our sources can still be explained with a smooth distribution of gas and a clumpy distribution of dust. Furthermore, we explored the torus dust-to-gas ratio, finding that it is [0.01–1] times that of the interstellar medium. Conclusions. The results presented in this paper suggest that the distribution of the gas and dust in AGN is complex. We find at least six scenarios to explain the observed properties of our sample. In these scenarios, three gas–dust distribution combinations are possible: clumpy–clumpy, smooth–smooth, and smooth–clumpy. Most of them are in agreement with the notion that gas could also be located in the dust-free region, which is consistent with the dust-to-gas ratio found.

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Seymour, Nick, D. Stern i C. De Breuck. "The Stellar Mass Distribution of Powerful Radio Galaxies Across 1 < z < 5.2". Proceedings of the International Astronomical Union 2, S235 (sierpień 2006): 427. http://dx.doi.org/10.1017/s1743921306010544.

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AbstractWe present the results of a comprehensive Spitzer survey of 70 radio galaxies across 1 < z < 5.2. Using IRAC (3.6–8.0μm), IRS (16 μm) and MIPS (24–160 μm) imaging, we decompose the rest-frame optical to infrared spectral energy distributions into stellar, AGN, and dust components and determine the contribution of host galaxy stellar emission at rest-frame 1.6 μm (H-band). We find that the fraction of emitted light at rest-frame 1.6 μm from stars is >80% for over half the high redshift radio galaxies. The other radio galaxies have 1.6 μm stellar fractions spanning the range 20–80%. The resultant stellar luminosities imply stellar masses of 1011−12M⊙, independent of redshift, indicating that radio galaxies are amoungst the most massive galaxies observed over this redshift range. Powerful radio galaxies tend to lie in a similar region of mid-IR color-color space as unobscured AGN, despite the inferred stellar contribution to their shorter-wavelength, mid-IR SEDs. The stellar fraction of the rest-frame 1.6 μm luminosity has no correlation with redshift, radio luminosity, or rest-frame mid-IR (5 μm) luminosity. The bolometric energy output of these sources is dominated by the infrared, and the mid-IR luminosities are found to be similar to that of lower redshift (z < 1) radio galaxies. As expected, these exceptionally high mid-IR luminosities are consistent with an obscured, highly-accreting AGN. A weak, but significant, correlation of stellar mass with radio luminosity is found, consistent with earlier results.

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