scholarly journals Optical heating of doped semiconductor nanocylinders supporting quasi-BIC modes

2021 ◽  
Vol 2015 (1) ◽  
pp. 012129
Author(s):  
Daniil Ryabov ◽  
Olesia Pashina ◽  
George Zograf ◽  
Sergey Makarov ◽  
Mihail Petrov

Abstract In the recent years, semiconductor and dielectric nanophotonic structures attracted a lot of attention for their resonant optical properties finding applications in thermal tuning and optical heating. Exciting high quality optical modes of both electric and magnetic nature in nanoresonators of high-index materials, one can effectively enhance optical absorption in such structures. Another big advantage of semiconductor materials is the ability to finely control the level of optical losses in visible and near infrared (near-IR) range through varying the doping level. In this work, we show theoretically that by moderate carrier doping of silicon via donors from group V materials one can achieve effective heating of nanoresonators. We show that by tuning the doping level of crystalline silicon supporting high quality non-radiative modes based on quasi bound states in the continuum one can achieve strong heating in near-IR under continuous wave regime illumination. We believe that our finding will pave the way for an efficient semiconductor near-IR all-optical sensors and nanoheaters.

2020 ◽  
Author(s):  
Michael Rolletter ◽  
Emmanuel Assaf ◽  
Mohamed Assali ◽  
Hendrik Fuchs ◽  
Christa Fittschen

<p>Acetylperoxy radicals (CH<sub>3</sub>C(O)O<sub>2</sub>) play an important role in the tropospheric chemistry. They are produced by the photooxidation of most emitted biogenic non-methane hydrocarbons. Recent studies show that the CH<sub>3</sub>C(O)O<sub>2</sub> + HO<sub>2</sub> reaction, which is the most important tropospheric loss reaction of acetylperoxy radicals in regions that are dominated by biogenic emissions (low NO emissions), does not only lead to radical chain terminating products but can also regenerate OH. The competing secondary chemistry, e. g., the CH<sub>3</sub>C(O)O<sub>2</sub> self-reaction, complicate kinetic measurements. The detection of acetylperoxy radicals in previous kinetic laboratory studies was mainly done in the UV region. However, the spectral overlap of different peroxy species in this region is prone to systematic errors in the quantitative detection. These complications can be avoided, if acetylperoxy radicals are detected by absorption in the near IR.</p><p>In our work, the near infrared CH<sub>3</sub>C(O)O<sub>2</sub> spectrum was measured in the spectral ranges from 6094 cm<sup>-1</sup> to 6180 cm<sup>-1</sup> and 6420 cm<sup>-1</sup> to 6600 cm<sup>-1</sup>. CH<sub>3</sub>C(O)O<sub>2</sub> radicals were generated by pulsed photolysis of a acetaldehyde/Cl<sub>2</sub>/O<sub>2</sub> mixture at 351 nm and were subsequently detected by time-resolved continuous-wave cavity ring-down spectroscopy (cw-CRDS). Experiments were done at 67 hPa in synthetic air and helium. The absorption cross sections of eight discrete absorption lines were determined relative to the absorption cross section of HO<sub>2</sub>, which has previously been reported.</p>


2007 ◽  
Vol 344 ◽  
pp. 745-750 ◽  
Author(s):  
Luigi Tricarico ◽  
Regula Spina ◽  
Donato Sorgente ◽  
A. Ancona ◽  
T. Sibillano ◽  
...  

Laser butt-welding of AA5083 has been investigated using a high quality CO2 laser in continuous wave regime. The effect of laser power, welding speed and specimen thickness on mechanical properties of the welded joints were evaluated by employing a general full factorial experimental plan design. The experimental results indicate important suggestion to choose proper combinations of process parameters and achieve high strength butt welded joints.


2020 ◽  
Vol 92 (2) ◽  
pp. 20101
Author(s):  
Behnam Kheyraddini Mousavi ◽  
Morteza Rezaei Talarposhti ◽  
Farshid Karbassian ◽  
Arash Kheyraddini Mousavi

Metal-assisted chemical etching (MACE) is applied for fabrication of silicon nanowires (SiNWs). We have shown the effect of amorphous sheath of SiNWs by treating the nanowires with SF6 and the resulting reduction of absorption bandwidth, i.e. making SiNWs semi-transparent in near-infrared (IR). For the first time, by treating the fabricated SiNWs with copper containing HF∕H2O2∕H2O solution, we have generated crystalline nanowires with broader light absorption spectrum, up to λ = 1 μm. Both the absorption and photo-luminescence (PL) of the SiNWs are observed from visible to IR wavelengths. It is found that the SiNWs have PL at visible and near Infrared wavelengths, which may infer presence of mechanisms such as forbidden gap transitions other can involvement of plasmonic resonances. Non-radiative recombination of excitons is one of the reasons behind absorption of SiNWs. Also, on the dielectric metal interface, the absorption mechanism can be due to plasmonic dissipation or plasmon-assisted generation of excitons in the indirect band-gap material. Comparison between nanowires with and without metallic nanoparticles has revealed the effect of nanoparticles on absorption enhancement. The broader near IR absorption, paves the way for applications like hyperthermia of cancer while the optical transition in near IR also facilitates harvesting electromagnetic energy at a broad spectrum from visible to IR.


Nanophotonics ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1081-1086 ◽  
Author(s):  
Abdoulaye Ndao ◽  
Liyi Hsu ◽  
Wei Cai ◽  
Jeongho Ha ◽  
Junhee Park ◽  
...  

AbstractOne of the key challenges in biology is to understand how individual cells process information and respond to perturbations. However, most of the existing single-cell analysis methods can only provide a glimpse of cell properties at specific time points and are unable to provide cell secretion and protein analysis at single-cell resolution. To address the limits of existing methods and to accelerate discoveries from single-cell studies, we propose and experimentally demonstrate a new sensor based on bound states in the continuum to quantify exosome secretion from a single cell. Our optical sensors demonstrate high-sensitivity refractive index detection. Because of the strong overlap between the medium supporting the mode and the analytes, such an optical cavity has a figure of merit of 677 and sensitivity of 440 nm/RIU. Such results facilitate technological progress for highly conducive optical sensors for different biomedical applications.


Author(s):  
Cong Shen ◽  
Yan Qing Zhu ◽  
Zixiao Li ◽  
Jingling Li ◽  
Hong Tao ◽  
...  

InP quantum dots (QDs) are considered as the most promising alternative to Cd-based QDs with the lower toxicity and emission spectrum tunability ranging from visible to near-infrared region. Although high-quality...


Author(s):  
Lorenzo Cotrozzi

AbstractSustainable forest management is essential to confront the detrimental impacts of diseases on forest ecosystems. This review highlights the potential of vegetation spectroscopy in improving the feasibility of assessing forest disturbances induced by diseases in a timely and cost-effective manner. The basic concepts of vegetation spectroscopy and its application in phytopathology are first outlined then the literature on the topic is discussed. Using several optical sensors from leaf to landscape-level, a number of forest diseases characterized by variable pathogenic processes have been detected, identified and quantified in many country sites worldwide. Overall, these reviewed studies have pointed out the green and red regions of the visible spectrum, the red-edge and the early near-infrared as the spectral regions most sensitive to the disease development as they are mostly related to chlorophyll changes and symptom development. Late disease conditions particularly affect the shortwave-infrared region, mostly related to water content. This review also highlights some major issues to be addressed such as the need to explore other major forest diseases and geographic areas, to further develop hyperspectral sensors for early detection and discrimination of forest disturbances, to improve devices for remote sensing, to implement long-term monitoring, and to advance algorithms for exploitation of spectral data. Achieving of these goals will enhance the capability of vegetation spectroscopy in early detection of forest stress and in managing forest diseases.


2021 ◽  
Vol 3 (1) ◽  
pp. 73-91
Author(s):  
João Serrano ◽  
Shakib Shahidian ◽  
Ângelo Carapau ◽  
Ana Elisa Rato

Dryland pastures provide the basis for animal sustenance in extensive production systems in Iberian Peninsula. These systems have temporal and spatial variability of pasture quality resulting from the diversity of soil fertility and pasture floristic composition, the interaction with trees, animal grazing, and a Mediterranean climate characterized by accentuated seasonality and interannual irregularity. Grazing management decisions are dependent on assessing pasture availability and quality. Conventional analytical determination of crude protein (CP) and fiber (neutral detergent fiber, NDF) by reference laboratory methods require laborious and expensive procedures and, thus, do not meet the needs of the current animal production systems. The aim of this study was to evaluate two alternative approaches to estimate pasture CP and NDF, namely one based on near-infrared spectroscopy (NIRS) combined with multivariate data analysis and the other based on the Normalized Difference Vegetation Index (NDVI) measured in the field by a proximal active optical sensor (AOS). A total of 232 pasture samples were collected from January to June 2020 in eight fields. Of these, 96 samples were processed in fresh form using NIRS. All 232 samples were dried and subjected to reference laboratory and NIRS analysis. For NIRS, fresh and dry samples were split in two sets: a calibration set with half of the samples and an external validation set with the remaining half of the samples. The results of this study showed significant correlation between NIRS calibration models and reference methods for quantifying pasture quality parameters, with greater accuracy in dry samples (R2 = 0.936 and RPD = 4.01 for CP and R2 = 0.914 and RPD = 3.48 for NDF) than fresh samples (R2 = 0.702 and RPD = 1.88 for CP and R2 = 0.720 and RPD = 2.38 for NDF). The NDVI measured by the AOS shows a similar coefficient of determination to the NIRS approach with pasture fresh samples (R2 = 0.707 for CP and R2 = 0.648 for NDF). The results demonstrate the potential of these technologies for estimating CP and NDF in pastures, which can facilitate the farm manager’s decision making in terms of the dynamic management of animal grazing and supplementation needs.


2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Cheng Chen ◽  
Yizhen Wen ◽  
Shaoyang Cui ◽  
Xiangao Qi ◽  
Zhenhong Liu ◽  
...  

This paper presents a multichannel functional continuous-wave near-infrared spectroscopy (fNIRS) system, which collects data under a dual-level light intensity mode to optimize SNR for channels with multiple source-detector separations. This system is applied to classify different cortical activation states of the prefrontal cortex (PFC). Mental arithmetic, digit span, semantic task, and rest state were selected as four mental tasks. A deep forest algorithm is employed to achieve high classification accuracy. By employing multigrained scanning to fNIRS data, this system can extract the structural features and result in higher performance. The proposed system with proper optimization can achieve 86.9% accuracy on the self-built dataset, which is the highest result compared to the existing systems.


2012 ◽  
Vol 1 (4) ◽  
Author(s):  
Nelson Marquina ◽  
Roger Dumoulin-White ◽  
Arkady Mandel ◽  
Lothar Lilge

AbstractA randomized placebo-controlled clinical trial to evaluate an adjunctive treatment modality for pain associated with knee disorders was conducted utilizing a therapeutic laser system (low energy, non-surgical).The therapeutic laser system utilized a dual wavelength, multiple diode laser cluster probe with five super-pulsed 905 nm near-infrared (NIR) laser diodes, each emitting at 40 mW average power and four continuous wave 660 nm visible (VIS) red laser diodes, each emitting at 25 mW. It was used as an adjunctive modality providing 12 treatments, three times a week to a homogeneous patient population (n=126), in combination with standardized chiropractic techniques, to evaluate effectiveness on subjects presenting with osteoarthritis and knee pain. The primary endpoint was measured by the visual analog scale (VAS) to assess pain levels on a scale of 0–10. The success criteria for an individual patient in this study were identified as an improvement of 30% or more in the VAS from baseline to 12th treatment and/or an improvement of 20% or more in the VAS from baseline to 30-day follow-up evaluation.The data obtained in the study demonstrated that the present therapeutic laser system provided significant pain relief and osteoarthritic improvements in all primary evaluation criteria, with a statistical and clinical significance of


Small ◽  
2016 ◽  
Vol 12 (13) ◽  
pp. 1732-1743 ◽  
Author(s):  
Akshaya Bansal ◽  
Haichun Liu ◽  
Muthu Kumara Gnanasammandhan Jayakumar ◽  
Stefan Andersson-Engels ◽  
Yong Zhang

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