Near IR multichannel Raman spectroscopy with μm spatial resolution

1992 ◽  
Vol 50 (2) ◽  
pp. 1500-1501
Author(s):  
J. Barbillat ◽  
B. Roussel
Keyword(s):  
Spatial Resolution ◽  
Near Infrared ◽  
Low Frequency ◽  
Diffraction Limit ◽  
Small Samples ◽  
Optical Elements ◽  
Near Ir ◽  
Photodiode Arrays ◽  
Silicon Based ◽  
Anti Stokes

The techniques and capabilities of near infrared (NIR) multichannel microprobing are described in detail in this paper.The advantages and drawbacks of various kinds of instruments used to measure Raman spectra excited in the NIR spectral range have been extensively studied and compared. We demonstrate that a dispersive spectrometer specially designed to match the recently improved NIR multichannel detectors (silicon-based CCD,Germanium and InGaAs photodiode arrays) may provide better results than a Fourier Transform Interferometer in two fields:- spatial resolution close to the diffraction limit in a micro-Raman confocal configuration (1.5 to 2 μm) and- extension of the Raman spectrum to the low-frequency region (Stokes and Anti-Stokes).Moreover, to observe the excitation profiles of both resonance and fluorescence, a combined multichannel instrument covering the entire range from 0.4 to 1.5 μm enables the user to select the best conditions of measurement.For the study of very small samples (close to the diffraction limit),it is optically impossible to fill in the wide entrance aperture of the interferometer with the image of the sample while covering correctly the optical elements inside the interferometer.

Low-frequency multiplex CARS microscopy with a high-repetition near-infrared supercontinuum laser

2021 ◽  
Author(s):  
Yusuke Arashida ◽  
Atsushi Taninaka ◽  
Takayuki Ochiai ◽  
Hiroyuki Mogi ◽  
Shoji YOSHIDA ◽  
...  
Keyword(s):  
Near Infrared ◽  
High Efficiency ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
High Sensitivity ◽  
High Repetition ◽  
Spectrum Shaping ◽  
Crystal Phase Transition ◽  
Wavenumber Region ◽  
Anti Stokes

Abstract We have developed a multiplex Coherent anti-Stokes Raman scattering (CARS) microscope effective for low-wavenumber measurement by combining a high-repetition supercontinuum light source of 1064 nm and an infrared high-sensitivity InGaAs diode array. This system could observe the low-wavenumber region down to 55 cm-1 with high sensitivity. In addition, using spectrum shaping and spectrum modulation techniques, we simultaneously realized a wide bandwidth (<1800 cm-1), high wavenumber resolution (9 cm-1), high efficiency, and increasing signal to noise ratio by reducing the effect of the background shape in low-wavenumber region. Spatial variation of a sulfur crystal phase transition with metastable states was visualized.

Using Quantum Dots for Liquid-Phase Thermometry at Near-Infrared Wavelengths in Silicon Devices

2010 ◽  
Author(s):  
Myeongsub Kim ◽  
Minami Yoda
Keyword(s):  
Quantum Dots ◽  
Liquid Phase ◽  
Spatial Resolution ◽  
Near Infrared ◽  
Core Shell ◽  
Temperature Sensitive ◽  
Core Diameter ◽  
Silicon Devices ◽  
Near Ir ◽  
Visible Wavelengths

The need for new thermal management technologies to cool electronic components with their ever-increasing density and power requirements has renewed interest in techniques for measuring liquid-phase coolant temperatures, especially nonintrusive techniques with micron-scale spatial resolution. A variety of optical liquid-phase thermometry techniques exploit the changes in the emission characteristics of fluorescent, phosphorescent or luminescent tracers suspended in a liquid-phase coolant. Such techniques are nonintrusive and have micron-scale spatial resolution, but they also require optical access to both excite and image the emissions. Silicon (Si), the leading material for electronic devices, is opaque at visible wavelengths, but is partially transparent in the near-infrared (IR). To date, the only tracers that emit at near-IR wavelengths with reasonable quantum yield are IR quantum dots (IRQD), colloidal nanocrystals of semiconductor materials such as lead sulfide (PbS). Previous work has shown that the intensity of emissions at 1.55 μm from PbS IRQD suspended in toluene are temperature-sensitive, decreasing by as much as 15% as the temperature increased from 20 °C to 60 °C. The accuracy of temperature measurements using PbS IRQD was estimated to be about 5 °C, based on 95% confidence intervals, where the major limit on the accuracy of the technique was the poor photostability of this material [1]. Recently, a new method for creating a cadmium sulfide (CdS) overcoat layer on PbS “cores” has been developed [2]. The experimental results presented here on the temperature sensitivity of these PbS/CdS core-shell infrared quantum dots with an emission peak around 1.35 μm and a diameter of 5.7 nm (with a core diameter of 4 nm) suggest that these new core-shell structures are more temperature-sensitive than the PbS cores. These core-shell quantum dots, when suspended in toluene, were found to have a 0.5% decrease in emission power per °C increase in temperature at suspension temperatures ranging from 20 °C to 60 °C. The uncertainty in the liquid-phase temperatures derived from these emissions was estimated to be less than 0.3 °C based on the standard deviation. Furthermore, the PbS/CdS quantum dots were highly photostable, with a consistent response more than 100 days after suspension. These results imply that that these new IRQD can be used to measure liquid-phase coolant temperatures without disturbing the flow of coolant at an accuracy comparable to commercially available thermocouples in monolithic Si devices.

Fabrication of High-Index Refractive Microlenses for Near-Field Optics

1999 ◽  
Author(s):  
D. A. Fletcher ◽  
K. B. Crozier ◽  
G. S. Kino ◽  
C. F. Quate ◽  
K. E. Goodson
Keyword(s):  
Spatial Resolution ◽  
Near Infrared ◽  
Focal Point ◽  
Near Field ◽  
Numerical Aperture ◽  
Diffraction Limit ◽  
Index Of Refraction ◽  
Optical Systems ◽  
Optical Efficiency ◽  
Lens Formation

Abstract The minimum spatial resolution of optical systems in the diffraction limit is approximately the free space wavelength divided by twice the numerical aperture (NA) of the system. NA is defined as the product of the index of refraction at the focal point and the sine of the maximum convergence angle of the light. Resolution below the diffraction limit in air can be achieved with a solid immersion lens (SIL) by scanning a sample within the near field of a spot formed in a high refractive-index lens material in the manner of Mansfield and Kino (1990). This paper presents a technique for microfabricating high-NA SILs in silicon with diameters on the order of 10 μm. Silicon has a higher index than previously demonstrated SILs, and it transmits well in the mid-infrared and near-infrared wavelength ranges, making it an ideal choice for high-resolution thermometry and spectroscopy. However, traditional methods for manufacturing SILs are time consuming, labor intensive, and expensive and cannot typically be used to make lenses smaller than 1 mm in diameter. We review current microlens fabrication techniques and describe the fabrication process developed for this work. We include a method for lens formation using acetone vapor to reflow photoresist pillars that can be used to make aspherical as well as spherical lenses. Microlenses etched in single-crystal silicon with diameters on the order of 10 μm and NAs as high as 3.0 are shown. Wafer-scale fabrication offers the opportunity to integrate microlenses onto MEMs structures such as scanning probes for optical imaging, lithography, spectroscopy, and thermometry with high optical efficiency and spatial resolution.

A Low Cost Silicon Based Thermal Camera for Volcanic Applications

2021 ◽  
Author(s):  
Joshua Marks ◽  
Jonas Kuhn ◽  
Christopher Fuchs ◽  
Nicole Bobrowski ◽  
Ulrich Platt
Keyword(s):  
Spatial Resolution ◽  
Near Infrared ◽  
Low Cost ◽  
Digital Camera ◽  
Visible Spectrum ◽  
Sensitivity Study ◽  
Volcanic Gas ◽  
Infrared Wavelength ◽  
Volcanic Emission ◽  
Silicon Based

&lt;p class=&quot;western&quot; lang=&quot;en-GB&quot; align=&quot;justify&quot;&gt;Volcanic gases and the chemical reactions inside volcanic emission plumes are of great interest because of their impact on atmospheric processes and climate. The evolution of many volcanic gas compounds is most likely strongly dependent on the general physical conditions during the emission processes. Particularly, the knowledge about the temperature of the lava, i.e. the origin of the gases, is crucial.&lt;/p&gt; &lt;p class=&quot;western&quot; lang=&quot;en-GB&quot; align=&quot;justify&quot;&gt;Commercially available thermal cameras for the relevant temperature range (ca. 600-1200 &amp;#176;C) are still rather expensive, bulky, and have a limited spatial resolution.&lt;/p&gt; &lt;p class=&quot;western&quot; lang=&quot;en-GB&quot; align=&quot;justify&quot;&gt;We present an approach to use a compact (&amp;#8216;point and shoot&amp;#8217;) consumer digital camera with a silicon based detector as a thermometer to record the spatial temperature distribution and variations of volcanic lava. Silicon detectors are commonly sensitive in the near infrared wavelength range (until ca. 1100 nm), which readily allows measurements of temperatures above ca. 500 &amp;#176;C. The camera is modified to block the visible spectrum and the remaining colour filter (Bayer filter) characteristics are used to infer the temperature from differential intensity measurements.&lt;/p&gt; &lt;p class=&quot;western&quot; lang=&quot;en-GB&quot; align=&quot;justify&quot;&gt;In the frame of this work, we performed a sensitivity study and calibrated the camera with a heated wire in the range of 600-1100 &amp;#176;C. Besides the advantages of superior mobility and simple handling, the 16 megapixel spatial resolution of the temperature measurement allows resolving detailed temperature distributions in highly dynamic volcanic emission processes.&lt;/p&gt;

Plasmon-assisted interaction of Si with light, for cancer hyperthermia and electromagnetic energy harvest

2020 ◽  
Vol 92 (2) ◽  
pp. 20101
Author(s):  
Behnam Kheyraddini Mousavi ◽  
Morteza Rezaei Talarposhti ◽  
Farshid Karbassian ◽  
Arash Kheyraddini Mousavi
Keyword(s):  
Silicon Nanowires ◽  
Metallic Nanoparticles ◽  
Near Infrared ◽  
Optical Transition ◽  
Electromagnetic Energy ◽  
Energy Harvest ◽  
Absorption Enhancement ◽  
Ir Absorption ◽  
Absorption Mechanism ◽  
Near Ir

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.

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 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 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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