Optical properties study of In.08Ga.92As/GaAs using spectral reflectance, photoreflectance and near-infrared Photoluminescence

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.

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Plant ecophysiological processes in spectral profiles: perspective from a deciduous broadleaf forest

Journal of Plant Research ◽

10.1007/s10265-021-01302-7 ◽

2021 ◽

Author(s):

Hibiki M. Noda ◽

Hiroyuki Muraoka ◽

Kenlo Nishida Nasahara

Keyword(s):

Remote Sensing ◽

Optical Properties ◽

Spectral Reflectance ◽

Canopy Structure ◽

Terrestrial Ecosystems ◽

Optical Remote Sensing ◽

Canopy Reflectance ◽

Broadleaf Forest ◽

Leaf Optical Properties ◽

Deciduous Broadleaf Forest

AbstractThe need for progress in satellite remote sensing of terrestrial ecosystems is intensifying under climate change. Further progress in Earth observations of photosynthetic activity and primary production from local to global scales is fundamental to the analysis of the current status and changes in the photosynthetic productivity of terrestrial ecosystems. In this paper, we review plant ecophysiological processes affecting optical properties of the forest canopy which can be measured with optical remote sensing by Earth-observation satellites. Spectral reflectance measured by optical remote sensing is utilized to estimate the temporal and spatial variations in the canopy structure and primary productivity. Optical information reflects the physical characteristics of the targeted vegetation; to use this information efficiently, mechanistic understanding of the basic consequences of plant ecophysiological and optical properties is essential over broad scales, from single leaf to canopy and landscape. In theory, canopy spectral reflectance is regulated by leaf optical properties (reflectance and transmittance spectra) and canopy structure (geometrical distributions of leaf area and angle). In a deciduous broadleaf forest, our measurements and modeling analysis of leaf-level characteristics showed that seasonal changes in chlorophyll content and mesophyll structure of deciduous tree species lead to a seasonal change in leaf optical properties. The canopy reflectance spectrum of the deciduous forest also changes with season. In particular, canopy reflectance in the green region showed a unique pattern in the early growing season: green reflectance increased rapidly after leaf emergence and decreased rapidly after canopy closure. Our model simulation showed that the seasonal change in the leaf optical properties and leaf area index caused this pattern. Based on this understanding we discuss how we can gain ecophysiological information from satellite images at the landscape level. Finally, we discuss the challenges and opportunities of ecophysiological remote sensing by satellites.

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High performing flexible optoelectronic devices using thin films of topological insulator

Scientific Reports ◽

10.1038/s41598-020-80738-8 ◽

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.

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Assessment of optical properties in cerebral ischemic rats by using near infrared spectroscopy

2014 IEEE Conference on Biomedical Engineering and Sciences (IECBES) ◽

10.1109/iecbes.2014.7047621 ◽

2014 ◽

Author(s):

Wan-Chen Shao ◽

Chun-Wei Wu ◽

Chun-Man Yuan ◽

Jia-Jin Jason Chen

Keyword(s):

Optical Properties ◽

Infrared Spectroscopy ◽

Near Infrared Spectroscopy ◽

Near Infrared ◽

Cerebral Ischemic

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Structure and microstructure of near infrared-absorbing Au–Au2S nanoparticles

Journal of Materials Research ◽

10.1557/jmr.2007.0314 ◽

2007 ◽

Vol 22 (9) ◽

pp. 2531-2538 ◽

Cited By ~ 5

Author(s):

Mei Chee Tan ◽

Jackie Y. Ying ◽

Gan Moog Chow

Keyword(s):

Optical Properties ◽

Surface Segregation ◽

Near Infrared ◽

Small Degree ◽

Core Shell ◽

Shell Microstructure ◽

Absorption Bands ◽

Interfacial Effects ◽

Nir Absorption ◽

Structure And Microstructure

Near infrared (NIR) absorbing nanoparticles synthesized by the reduction of HAuCl4 with Na2S exhibited absorption bands at ∼530 nm, and in the NIR region of 650–1100 nm. The NIR optical properties were not found to be related to the earlier proposed Au2S–Au core-shell microstructure in previous studies. From a detailed study of the structure and microstructure of as-synthesized particles in this work, S-containing, Au-rich, multiply-twinned nanoparticles were found to exhibit NIR absorption. They consisted of amorphous AuxS (where x = 2), mostly well mixed within crystalline Au, with a small degree of surface segregation of S. Therefore, NIR absorption was likely due to interfacial effects on particle polarization from the introduction of AuxS into Au particles, and not the dielectric confinement of plasmons associated with a core-shell microstructure.

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