| 1. |
- Tobin, John J., et al.
(författare)
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The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. I. Identifying and Characterizing the Protostellar Content of the OMC-2 FIR4 and OMC-2 FIR3 Regions
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 886:1
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Tidskriftsartikel (refereegranskat)abstract
- We present Atacama Large Millimeter/submillimeter Array (0.87 mm) and Very Large Array (9 mm) observations toward OMC-2 FIR4 and OMC-2 FIR3 within the Orion integral-shaped filament, thought to be two of the nearest regions of intermediate-mass star formation. We characterize the continuum sources within these regions on ?40 au (01) scales and associated molecular line emission at a factor of ?30 better resolution than previous observations at similar wavelengths. We identify six compact continuum sources within OMC-2 FIR4, four in OMC-2 FIR3, and one additional source just outside OMC-2 FIR4. This continuum emission is tracing the inner envelope and/or disk emission on less than 100 au scales. HOPS-108 is the only protostar in OMC-2 FIR4 that exhibits emission from high-excitation transitions of complex organic molecules (e.g., methanol and other lines) coincident with the continuum emission. HOPS-370 in OMC-2 FIR3, with L;?;360 L, also exhibits emission from high-excitation methanol and other lines. The methanol emission toward these two protostars is indicative of temperatures high enough to thermally evaporate it from icy dust grains; overall, these protostars have characteristics similar to hot corinos. We do not identify a clear outflow from HOPS-108 in (CO)-C-12, but we find evidence of interaction between the outflow/jet from HOPS-370 and the OMC-2 FIR4 region. A multitude of observational constraints indicate that HOPS-108 is likely a low- to intermediate-mass protostar in its main mass accretion phase and is the most luminous protostar in OMC-2 FIR4. The high-resolution data presented here are essential for disentangling the embedded protostars from their surrounding dusty environments and characterizing them.
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| 2. |
- Tobin, John J., et al.
(författare)
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The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. II. A Statistical Characterization of Class 0 and Class i Protostellar Disks
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 890:2
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Tidskriftsartikel (refereegranskat)abstract
- We have conducted a survey of 328 protostars in the Orion molecular clouds with the Atacama Large Millimeter/submillimeter Array at 0.87 mm at a resolution of ∼0.″1 (40 au), including observations with the Very Large Array at 9 mm toward 148 protostars at a resolution of ∼0.″08 (32 au). This is the largest multiwavelength survey of protostars at this resolution by an order of magnitude. We use the dust continuum emission at 0.87 and 9 mm to measure the dust disk radii and masses toward the Class 0, Class I, and flat-spectrum protostars, characterizing the evolution of these disk properties in the protostellar phase. The mean dust disk radii for the Class 0, Class I, and flat-spectrum protostars are 44.9-3.4+5.8, 37.0-3.0+4.9, and 28.5-2.3+3.7 au, respectively, and the mean protostellar dust disk masses are 25.9-4.0+7.7, 14.9-2.2+3.8, 11.6-1.9+3.5 M⊙, respectively. The decrease in dust disk masses is expected from disk evolution and accretion, but the decrease in disk radii may point to the initial conditions of star formation not leading to the systematic growth of disk radii or that radial drift is keeping the dust disk sizes small. At least 146 protostellar disks (35% of 379 detected 0.87 mm continuum sources plus 42 nondetections) have disk radii greater than 50 au in our sample. These properties are not found to vary significantly between different regions within Orion. The protostellar dust disk mass distributions are systematically larger than those of Class II disks by a factor of >4, providing evidence that the cores of giant planets may need to at least begin their formation during the protostellar phase.
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| 3. |
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| 4. |
- Samoc, Marek, et al.
(författare)
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Nonlinear absorption and nonlinear refraction: Maximizing the merit factors
- 2012
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819489012 ; 8258, s. Art. no. 82580V-
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Konferensbidrag (refereegranskat)abstract
- Both nonlinear absorption and nonlinear refraction are effects that are potentially useful for a plethora of applications in photonics, nanophotonics and biophotonics. Despite substantial attention given to these phenomena by researchers studying the merits of disparate systems such as organic materials, hybrid materials, metal-containing molecules and nanostructures, it is virtually impossible to compare the results obtained on different materials when varying parameters of the light beams and different techniques are employed. We have attempted to address the problem by studying the properties of various systems in a systematic way, within a wide range of wavelengths, and including the regions of onephoton, two-photon and three-photon absorption. The objects of our studies have been typical nonlinear chromophores, such as π-conjugated molecules, oligomers and polymers, organometallics and coordination complexes containing transition metals, organometallic dendrimers, small metal-containing clusters, and nanoparticles of various kinds, including semiconductor quantum dots, plasmonic particles and rare-earth doped nanocrystals. We discuss herein procedures to quantify the nonlinear response of all of these systems, by defining and comparing the merit factors relevant for various applications.
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| 5. |
- Wittek, Steffen, et al.
(författare)
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Mode-Multiplexed Transmission within and Across Mode Groups of a Multimode-Fiber
- 2019
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Ingår i: 2019 Optical Fiber Communications Conference and Exhibition, OFC 2019 - Proceedings. - Washington, D.C. : OSA. - 9781943580538
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Konferensbidrag (refereegranskat)abstract
- We show mode-multiplexed transmission over individual mode groups up to 9 groups of a 27 km long graded-index multimode fiber. We also investigate transmission distances up to 500 km using a recirculating loop arrangement for the first 6 mode groups using QPSK and 16-QAM signals.
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| 6. |
- Choutagunta, Karthik, et al.
(författare)
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Modal Dynamics in Spatially Multiplexed Links
- 2019
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Ingår i: Optics InfoBase Conference Papers. - Washington, D.C. : OSA. - 2162-2701.
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Konferensbidrag (refereegranskat)abstract
- We investigate the vibration sensitivity of spatially multiplexed links by measuring the mode-coupling dynamics of a four-core coupled-core fiber and a reference single-mode fiber. We show that the speed of dynamics increases with mode count.
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| 7. |
- Deriushkina, Ekaterina, 1992, et al.
(författare)
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Characterisation of a Coupled-Core Fiber Using Dual-Comb Swept-Wavelength Interferometry
- 2021
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Ingår i: 2021 European Conference on Optical Communication, ECOC 2021.
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Konferensbidrag (refereegranskat)abstract
- We present a measurement of the transfer matrix of a coupled three-core fiber using a novel combination of swept-wavelength interferometry and dual-comb spectroscopy capable of measuring 1 THz bandwidth with a frequency resolution of 50 kHz with only a 25 GHz laser sweep.
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| 8. |
- Fontaine, Nicolas K., et al.
(författare)
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Digital turbulence compensation of free space optical link with multimode optical amplifier
- 2019
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Ingår i: IET Conference Publications. - : Institution of Engineering and Technology. ; 2019:CP765
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Konferensbidrag (refereegranskat)abstract
- We demonstrate digital turbulence compensation using a 12-spatial mode digital coherent receiver with a multimode preamplifier that provides a 6-dB sensitivity improvement. This combination acts similarly to ideal lossless adaptive optics. Coherent superposition of 12 spatial-modes reduced median BER from 0.1 to 1×10-5 compared to traditional single-mode detection.
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| 9. |
- Haffner, Christian, et al.
(författare)
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Nano–opto-electro-mechanical switches operated at CMOS-level voltages
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 366:6467, s. 860-864
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Tidskriftsartikel (refereegranskat)abstract
- Combining reprogrammable optical networks with complementary metal-oxide semiconductor (CMOS) electronics is expected to provide a platform for technological developments in on-chip integrated optoelectronics. We demonstrate how opto-electro-mechanical effects in micrometer-scale hybrid photonic-plasmonic structures enable light switching under CMOS voltages and low optical losses (0.1 decibel). Rapid (for example, tens of nanoseconds) switching is achieved by an electrostatic, nanometer-scale perturbation of a thin, and thus low-mass, gold membrane that forms an air-gap hybrid photonic-plasmonic waveguide. Confinement of the plasmonic portion of the light to the variable-height air gap yields a strong opto-electro-mechanical effect, while photonic confinement of the rest of the light minimizes optical losses. The demonstrated hybrid architecture provides a route to develop applications for CMOS-integrated, reprogrammable optical systems such as optical neural networks for deep learning.
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| 10. |
- Huang, Yetian, et al.
(författare)
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Optical Broadcasting Employing Incoherent And Low-Coherence Spatial Modes for Bi-Directional Optical Wireless Communications
- 2021
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 39:3, s. 833-838
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Tidskriftsartikel (refereegranskat)abstract
- We introduce recently developed space division multiplexing (SDM)-associated technologies into optical wireless communications (OWC) and propose to use incoherent and low-coherence spatial modes to realize optical broadcasting with reliable performance by mitigating coherent interference. We experimentally demonstrate reconfigurable optical beam steering using a programmable multi-plane light conversion (MPLC)-based mode multiplexer (MMUX) and realize point-to-multi-point optical wireless communications with low-loss up-link optical beam combining and reach extension using multimode fiber (MMF). Both incoherent and low-coherence spatial modes can be generated employing the cost-efficient components such as multimode vertical cavity surface emitting laser (MM-VCSEL) and broadband amplified spontaneous emission (ASE) noise source.
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