scholarly journals Infrared Speckle Methods

1984 ◽  
Vol 79 ◽  
pp. 309-336 ◽  
Author(s):  
A. Chelli
Keyword(s):  
Optical Properties ◽  
Image Reconstruction ◽  
Spatial Resolution ◽  
Near Infrared ◽  
Speckle Interferometry ◽  
Reconstruction Methods ◽  
Interferometry Method ◽  
Large Telescopes

I-INTRODUCTION The speckle interferometry method has been introduced in 1970 by A. Labeyrie who showed in the visible dcmain that it was possible to reach the limiting spatial resolution of large telescopes. From 1977, the method is extended to the near infrared between 2 and 5ym (Lena, 1977; Wade and Selby, 1978) ,7 years later infrared speckle systems are operating on several large telescopes (ESO, KPNO, AAT, UKIRT, CFHT... ).The speckle interferometry method has allowed to better understanding the optical properties of the atmosphere, especially owing to the work of F.Roddier (Roddier, 1981). It has raised new problems like the phase restitution of the object spectrum and has largely contributed to the development of image reconstruction methods.

scholarly journals Interférométrie et réflectométrie haute résolution en lumière incohérente : modélisation d'interférogrammes

2000 ◽  
Vol 77 (9) ◽  
pp. 685-692
Author(s):  
C Lupi ◽  
E Tanguy ◽  
C Boisrobert ◽  
F de Fornel
Keyword(s):  
Optical Properties ◽  
Spatial Resolution ◽  
White Light ◽  
Near Infrared ◽  
Michelson Interferometer ◽  
Optical Power ◽  
Source Spectrum ◽  
Optical Fibres ◽  
Low Coherence ◽  
Haute Résolution

We report on low-coherence, near-infrared reflectometry applied to optical fibres, waveguides, and coupling devices to detect the echoes due to reflective propagation defects and measure their optical properties — losses or attenuation, dispersion. This technique, based on interferometry, leads to the highest spatial resolution and the lowest detectable reflected optical power. We scan the reference arm of our Michelson interferometer around the ``white light fringe'' position and obtain interferograms whose envelopes and fringes contain information on the light source spectrum and the reflectivity of the test arm. Theoretical and experimental results are compared. Examples are given and show that numerical simulations are needed to understand the signatures of the reflectors and get to their physical structures.

scholarly journals Speckle Interferometry and Image Reconstruction

1979 ◽  
Vol 50 ◽  
pp. 33-1-33-12
Author(s):  
Gerd P. Weigelt
Keyword(s):  
Image Reconstruction ◽  
Binary Stars ◽  
Binary Star ◽  
Speckle Interferometry ◽  
Reference Star ◽  
Evaluation Procedures ◽  
Reconstruction Methods ◽  
High Resolution Images ◽  
Speckle Holography ◽  
Triple Star

AbstractThe angular resolution of conventional astrophotography is limited to about 1 sec of arc due to image degradation by the atmosphere and telescope aberrations. Higher resolution can be achieved by Labeyrie's speckle interferometry, which yields the autocorrelation of astronomical objects with diffraction-limited resolution, e.g. 0.02 sec of arc with 5m telescope aperture.We have investigated modifications of speckle interferometry, which yield diffraction-limited images. We investigated (1) “speckle holography” for image reconstruction of objects near an unresolvable point source (reference star), (2) “speckle masking” for image reconstruction of binary stars (without a reference star), and (3) “phase flipping” for image reconstruction of centro-symmetric objects. Together these three image reconstruction methods represent a set of speckle evaluation procedures, which can yield high resolution images of most astronomical objects that are bright enough for speckle interferometry. Speckle holography was already applied to astronomical objects. We reconstructed real images of the binary star Zeta Cancri A-B and the triple star ADS 3358 A-B-C ( 0.07 sec of arc resolution with 1.8m telescope aperture).

scholarly journals Line observations of the 30-Dor complex and N159A5 with the MPE imaging NIR spectrometer FAST

1991 ◽  
Vol 148 ◽  
pp. 205-206 ◽  
Author(s):  
A. Krabbe ◽  
J. Storey ◽  
V. Rotaciuc ◽  
S. Drapatz ◽  
R. Genzel
Keyword(s):  
Spatial Resolution ◽  
Molecular Hydrogen ◽  
Near Infrared ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Emission Lines ◽  
Resolving Power ◽  
Max Planck ◽  
First Time ◽  
Infrared Array

Images with subarcsec spatial resolution in the light of near-infrared atomic (Bry) and molecular hydrogen H2 (S(1) v=1-0) emission lines were obtained for some extended, pointlike objects in the Large Magellanic Cloud (LMC) for the first time. We used the Max-Planck-Institut für extraterrestrische Physik (MPE) near-infrared array spectrometer FAST (image scale 0.8”/pix, spectral resolving power 950) at the ESO/MPI 2.2m telescope, La Silla. We present some results on the 30-Dor complex and N159A5.

scholarly journals The Effect of Nitrogen Incorporation on the Optical Properties of Si-Rich a-SiCx Films Deposited by VHF PECVD

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 637
Author(s):  
Hongliang Li ◽  
Zewen Lin ◽  
Yanqing Guo ◽  
Jie Song ◽  
Rui Huang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Near Infrared ◽  
Chemical Vapor ◽  
Wide Bandgap ◽  
Nonradiative Recombination ◽  
Very High Frequency ◽  
N Content ◽  
High Frequency Plasma ◽  
Frequency Plasma ◽  
N Incorporation

The influence of N incorporation on the optical properties of Si-rich a-SiCx films deposited by very high-frequency plasma-enhanced chemical vapor deposition (VHF PECVD) was investigated. The increase in N content in the films was found to cause a remarkable enhancement in photoluminescence (PL). Relative to the sample without N incorporation, the sample incorporated with 33% N showed a 22-fold improvement in PL. As the N content increased, the PL band gradually blueshifted from the near-infrared to the blue region, and the optical bandgap increased from 2.3 eV to 5.0 eV. The enhancement of PL was suggested mainly from the effective passivation of N to the nonradiative recombination centers in the samples. Given the strong PL and wide bandgap of the N incorporated samples, they were used to further design an anti-counterfeiting label.

scholarly journals Mineral Detection Using Sharpened VNIR and SWIR Bands of Worldview-3 Satellite Imagery

2021 ◽  
Vol 13 (10) ◽  
pp. 5518
Author(s):  
Honglyun Park ◽  
Jaewan Choi
Keyword(s):  
Spatial Resolution ◽  
Satellite Imagery ◽  
Near Infrared ◽  
False Negative ◽  
Similarity Score ◽  
Majority Voting ◽  
Similarity Analysis ◽  
Spectral Angle Mapper ◽  
Mineral Detection ◽  
Shortwave Infrared

Worldview-3 satellite imagery provides panchromatic images with a high spatial resolution and visible near infrared (VNIR) and shortwave infrared (SWIR) bands with a low spatial resolution. These images can be used for various applications such as environmental analysis, urban monitoring and surveying for sustainability. In this study, mineral detection was performed using Worldview-3 satellite imagery. A pansharpening technique was applied to the spatial resolution of the panchromatic image to effectively utilize the VNIR and SWIR bands of Worldview-3 satellite imagery. The following representative similarity analysis techniques were implemented for the mineral detection: the spectral angle mapper (SAM), spectral information divergence (SID) and the normalized spectral similarity score (NS3). In addition, pixels that could be estimated to indicate minerals were calculated by applying an empirical threshold to each similarity analysis result. A majority voting technique was applied to the results of each similarity analysis and pixels estimated to indicate minerals were finally selected. The results of each similarity analysis were compared to evaluate the accuracy of the proposed methods. From that comparison, it could be confirmed that false negative and false positive rates decreased when the methods proposed in the present study were applied.

scholarly journals High performing flexible optoelectronic devices using thin films of topological insulator

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Animesh Pandey ◽  
Reena Yadav ◽  
Mandeep Kaur ◽  
Preetam Singh ◽  
Anurag Gupta ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Nonlinear Optical ◽  
Near Infrared ◽  
Optoelectronic Devices ◽  
Nonlinear Optical Properties ◽  
Metallic Surface ◽  
Strong Light ◽  
High Performing ◽  
Decay Times

AbstractTopological insulators (TIs) possess exciting nonlinear optical properties due to presence of metallic surface states with the Dirac fermions and are predicted as a promising material for broadspectral phodotection ranging from UV (ultraviolet) to deep IR (infrared) or terahertz range. The recent experimental reports demonstrating nonlinear optical properties are mostly carried out on non-flexible substrates and there is a huge demand for the fabrication of high performing flexible optoelectronic devices using new exotic materials due to their potential applications in wearable devices, communications, sensors, imaging etc. Here first time we integrate the thin films of TIs (Bi2Te3) with the flexible PET (polyethylene terephthalate) substrate and report the strong light absorption properties in these devices. Owing to small band gap material, evolving bulk and gapless surface state conduction, we observe high responsivity and detectivity at NIR (near infrared) wavelengths (39 A/W, 6.1 × 108 Jones for 1064 nm and 58 A/W, 6.1 × 108 Jones for 1550 nm). TIs based flexible devices show that photocurrent is linearly dependent on the incident laser power and applied bias voltage. Devices also show very fast response and decay times. Thus we believe that the superior optoelectronic properties reported here pave the way for making TIs based flexible optoelectronic devices.

scholarly journals Regulating disordered plasmonic nanoparticles into polarization sensitive metasurfaces

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Shulei Li ◽  
Mingcheng Panmai ◽  
Shaolong Tie ◽  
Yi Xu ◽  
Jin Xiang ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Spatial Resolution ◽  
Metallic Nanoparticles ◽  
Near Infrared ◽  
Optical Memory ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Optical Diffraction ◽  
Plasmonic Nanoparticles ◽  
Direct Laser

Abstract Metasurfaces composed of regularly arranged and deliberately oriented metallic nanoparticles can be employed to manipulate the amplitude, phase and polarization of an incident electromagnetic wave. The metasurfaces operating in the visible to near infrared spectral range rely on the modern fabrication technologies which offer a spatial resolution beyond the optical diffraction limit. Although direct laser writing is an alternative to the fabrication of nanostructures, the achievement of regular nanostructures with deep-subwavelength periods by using this method remains a big challenge. Here, we proposed and demonstrated a novel strategy for regulating disordered plasmonic nanoparticles into nanogratings with deep-subwavelength periods and reshaped nanoparticles by using femtosecond laser pulses. The orientations of the nanogratings depend strongly on the polarization of the femtosecond laser light. Such nanogratings exhibit reflection and polarization control over the reflected light, enabling the realization of polarization sensitive optical memory and color display with high spatial resolution and good chromacity.

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