Performance of a Spatial-Filter-Equipped Single Monochromator for Raman Spectroscopy

1994 ◽  
Vol 48 (6) ◽  
pp. 720-723 ◽  
Author(s):  
Mark O. Trulson ◽  
Horst B. Lueck ◽  
Donald M. Friedrich
Keyword(s):  
Raman Spectroscopy ◽  
Laser Excitation ◽  
Scattered Light ◽  
Spatial Filtering ◽  
Spatial Filter ◽  
Stray Light ◽  
Ultraviolet Region ◽  
Excitation Wavelength ◽  
Excitation Light ◽  
Diffuse Background

A technique for reducing stray-light artifacts in Raman spectroscopy is described. The performance of a spatial filter at the output of a single monochromator is reported. The filter reduces both the diffuse background and the scattered-light artifacts encountered in single monochromators while maintaining high luminous throughput. Unlike other wavelength-selective methods for rejecting laser-excitation light (such as use of holographic edge or notch filters), spatial filtering of scattering artifacts may be used with any excitation wavelength. This is an advantage for Raman spectroscopy in the quartz ultraviolet region where holographic filters are not yet available. The enhanced ability to observe low-wavenumber scattering with an optical multichannel detector on a single monochromator is a particular advantage of the method.

Raman Spectroscopy over Optical Fibers with the Use of a Near-IR FT Spectrometer

1988 ◽  
Vol 42 (8) ◽  
pp. 1558-1563 ◽  
Author(s):  
D. D. Archibald ◽  
L. T. Lin ◽  
D. E. Honigs
Keyword(s):  
Raman Spectroscopy ◽  
Optical Fiber ◽  
Optical Fibers ◽  
Scattered Light ◽  
Background Spectrum ◽  
Excitation Light ◽  
Analyte Signal ◽  
Near Ir ◽  
Potential Applications ◽  
Ft Ir

A commercial Fourier transform infrared (FT-IR) spectrometer was modified for remote near-IR Raman spectroscopy. In one configuration, a single optical fiber was used to guide the excitation light to the specimen and to collect scattered light from the specimen. In an alternative configuration, separate fibers were used for excitation and collection. The optical fiber probes were used to record the Raman spectra of both liquid and solid specimens. The Raman scattering of the optical fibers interfered with the analyte signal. This fiber interference was affected by the optical properties of the specimen and the optical sampling configuration. These interferences were partially removed by subtracting a background spectrum. Potential applications and improvements are discussed.

scholarly journals Exploring the effect of laser excitation wavelength on signal recovery with deep tissue transmission Raman spectroscopy

The Analyst ◽  
2016 ◽  
Vol 141 (20) ◽  
pp. 5738-5746 ◽  
Author(s):  
Adrian Ghita ◽  
Pavel Matousek ◽  
Nicholas Stone
Keyword(s):  
Raman Spectroscopy ◽  
Breast Tissue ◽  
Laser Excitation ◽  
Excitation Wavelength ◽  
Signal Recovery ◽  
Deep Tissue ◽  
Transmission Raman

The aim of this research was to find the optimal Raman excitation wavelength to attain the largest possible sensitivity in deep Raman spectroscopy of breast tissue.

Spatial filtering of signals with spectrum overlapping

2019 ◽  
pp. 27-33
Author(s):  
M. E. Shevchenko ◽  
A. V. Gorovoy ◽  
S. N. Solovyov
Keyword(s):  
Antenna Arrays ◽  
A Priori ◽  
Spatial Filtering ◽  
Spatial Filter ◽  
Radio Sources ◽  
Probability Of Error ◽  
Shift Keying ◽  
A Priori Uncertainty

The paper considers the spatial filtering methods of signals with spectrum overlapping under conditions of a priori uncertainty of the directions of arrival from radio sources. The estimates of the directions of signals arrival obtained by ESPRIT or MUSIC are used in order to build a spatial filter. It is shown that when using ESPRIT, unlike MUSIC, an additional calculations of filter coefficients based on estimates of the directions of signals arrival are not required, and the quadrature components of the signals are formed simultaneously with estimates of the direction of their arrival. The probability of error performances of minimum shift keying signals which were divided by spatial filtering on the basis of ESPRIT and MUSIC using seven-element circular and angular antenna arrays are given.

scholarly journals Fabrication-friendly polarization-sensitive plasmonic grating for optimal surface-enhanced Raman spectroscopy

2020 ◽  
Vol 16 (1) ◽  
Author(s):  
Arpan Dutta ◽  
Tarmo Nuutinen ◽  
Khairul Alam ◽  
Antti Matikainen ◽  
Peng Li ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Fill Factor ◽  
Surface Enhanced Raman Spectroscopy ◽  
Transverse Magnetic ◽  
Raman Signal ◽  
Optical Resonance ◽  
Excitation Light ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Plasmonic Gratings

Abstract Plasmonic nanostructures are widely utilized in surface-enhanced Raman spectroscopy (SERS) from ultraviolet to near-infrared applications. Periodic nanoplasmonic systems such as plasmonic gratings are of great interest as SERS-active substrates due to their strong polarization dependence and ease of fabrication. In this work, we modelled a silver grating that manifests a subradiant plasmonic resonance as a dip in its reflectivity with significant near-field enhancement only for transverse-magnetic (TM) polarization of light. We investigated the role of its fill factor, commonly defined as a ratio between the width of the grating groove and the grating period, on the SERS enhancement. We designed multiple gratings having different fill factors using finite-difference time-domain (FDTD) simulations to incorporate different degrees of spectral detunings in their reflection dips from our Raman excitation (488 nm). Our numerical studies suggested that by tuning the spectral position of the optical resonance of the grating, via modifying their fill factor, we could optimize the achievable SERS enhancement. Moreover, by changing the polarization of the excitation light from transverse-magnetic to transverse-electric, we can disable the optical resonance of the gratings resulting in negligible SERS performance. To verify this, we fabricated and optically characterized the modelled gratings and ensured the presence of the desired detunings in their optical responses. Our Raman analysis on riboflavin confirmed that the higher overlap between the grating resonance and the intended Raman excitation yields stronger Raman enhancement only for TM polarized light. Our findings provide insight on the development of fabrication-friendly plasmonic gratings for optimal intensification of the Raman signal with an extra degree of control through the polarization of the excitation light. This feature enables studying Raman signal of exactly the same molecules with and without electromagnetic SERS enhancements, just by changing the polarization of the excitation, and thereby permits detailed studies on the selection rules and the chemical enhancements possibly involved in SERS.

scholarly journals Degradation of multiphoton signal and resolution when focusing through a planar interface with index mismatch: Analytical approximation and numerical investigation

2018 ◽  
Vol 11 (04) ◽  
pp. 1850020
Author(s):  
Ping Qiu ◽  
Chen He
Keyword(s):  
Spherical Aberration ◽  
Numerical Aperture ◽  
Analytical Approximation ◽  
Planar Interface ◽  
Excitation Wavelength ◽  
Physical Parameters ◽  
Approximate Analytical Expression ◽  
Excitation Light ◽  
Analytical Expression ◽  
Imaging Depth

Multiphoton microscopy (MPM) is an invaluable tool for visualizing subcellular structures in biomedical and life sciences. High-numerical-aperture (NA) immersion objective lenses are used to deliver excitation light to focus inside the biological tissue. The refractive index of tissue is commonly different from that of the immersion medium, which introduces spherical aberration, leading to signal and resolution degradation as imaging depth increases. However, the explicit dependence of this index mismatch-induced aberration on the involved physical parameters is not clear, especially its dependence on index mismatch. Here, from the vectorial equations for focusing through a planar interface between materials of mismatched refractive indices, we derive an approximate analytical expression for the spherical aberration. The analytical expression explicitly reveals the dependence of spherical aberration on index mismatch, imaging depth and excitation wavelength, from which we can expect the following qualitative behaviors: (1) Multiphoton signal and resolution degradation is less for longer excitation wavelength, (2) a longer wavelength tolerates a higher index mismatch, (3) a longer wavelength tolerates a larger imaging depth and (4) both signal and resolution degradations show the same dependence on imaging depth, regardless of NA or immersion on the condition that the integration angle is the same. Detailed numerical simulation results agree quite well with the above expectations based on the analytical approximation. These theoretical results suggest the use of long excitation wavelength to better suppress index mismatch-induced signal and resolution degradation in deep-tissue MPM.

scholarly journals Investigation of the influence of plasma source power on the properties of magnetron sputtered Ta2O5 thin films

2021 ◽  
Vol 255 ◽  
pp. 03005
Author(s):  
Manuel Bärtschi ◽  
Daniel Schachtler ◽  
Silvia Schwyn-Thöny ◽  
Thomas Südmeyer ◽  
Roelene Botha
Keyword(s):  
Thin Films ◽  
Scattered Light ◽  
Plasma Source ◽  
Stray Light ◽  
Optical Losses ◽  
Coating Materials ◽  
Source Power ◽  
Light Losses ◽  
Interference Coating ◽  
Deposition Processes

To enable the production of sophisticated optical interference coating designs, coatings with very low absorption and stray light losses and excellent layer thickness deposition accuracy are required. The selection and optimization of suitable coating materials and deposition processes are consequently essential. This study investigated the influence of the plasma source power on the optical properties, layer uniformity and stress, scattered light behavior and optical losses of magnetron sputtered Ta2O5 thin films.

Chemical Bath Deposition of Lead Sulphide (PbS) Thin Film and their Characterization

2013 ◽  
Vol 209 ◽  
pp. 111-115 ◽  
Author(s):  
Sandip V. Bhatt ◽  
M.P. Deshpande ◽  
Bindiya H. Soni ◽  
Nitya Garg ◽  
Sunil H. Chaki
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Raman Spectroscopy ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
Excitation Wavelength ◽  
Face Centered Cubic ◽  
Phonon Modes ◽  
Lead Sulphide ◽  
X Ray

Thin film deposition of PbS is conveniently carried out by chemical reactions of lead acetate with thiourea at room temperature. Energy dispersive analysis of X-ray (EDAX), X-ray diffraction (XRD), selected area electron diffraction patterns (SAED), UV-Vis-NIR spectrophotometer, Scanning Electron Microscopy (SEM), Atomic force microscopy (AFM), Photoluminescence (PL) and Raman spectroscopy techniques are used for characterizing thin films. EDAX spectra shows that no impurity is present and XRD pattern indicates face centered cubic structure of PbS thin films. The average crystallite size obtained using XRD is about 15nm calculated using Scherrer’s formula and that determined from Hall-Williamson plot was found to be 18nm. SAED patterns indicate that the deposited PbS thin films are polycrystalline in nature. Blue shift due to quantum confinement was seen from the UV-Vis-NIR absorption spectra of thin film in comparison with bulk PbS. The Photoluminescence spectra obtained for thin film with different excitation sources shows sharp emission peaks at 395nm and its intensity of photoluminescence increases with increasing the excitation wavelength. Raman spectroscopy of deposited thin film was used to study the optical phonon modes at an excitation wavelength of 488nm using (Ar+) laser beam.

Intense Photoluminescence and Photoluminescence Enhancement of Silicon Nanocrystals by Ultraviolet Irradiation

2007 ◽  
Vol 31 ◽  
pp. 74-76 ◽  
Author(s):  
P.T. Huy ◽  
P.H. Duong
Keyword(s):  
Silicon Nanocrystals ◽  
Room Temperature ◽  
Laser Excitation ◽  
Uv Light ◽  
Irradiation Time ◽  
Excitation Wavelength ◽  
Nonradiative Recombination ◽  
Emission Yield ◽  
Recombination Centers ◽  
Pl Intensity

Photoluminescence (PL) from silicon nanocrystals deposited on top of silica-glass template and from silicon nanocrystals in nc_Si/SiO2 multilayer films were studied as a function of ultraviolet (UV) laser irradiation time in vacuum. Both the films exhibit intense visible PL at room temperature under laser excitation. It was found that upon prolong irradiation time using a He-Cd laser (325 nm) the PL intensity of the films was spectacularly enhanced. The process is reversible and does not happen with excitation wavelength longer than 400 nm. Upon introducing air into the measurement chamber, a rapid decrease of the PL intensity was recorded. This observation suggests that the UV light may lead to modification of nonradiative recombination centers in the films and thus improves the emission yield of silicon nanocrystals.

Rhodium nanocubes and nanotripods for highly sensitive ultraviolet surface-enhanced Raman spectroscopy

The Analyst ◽  
2018 ◽  
Vol 143 (10) ◽  
pp. 2310-2322 ◽  
Author(s):  
Rupali Das ◽  
R. K. Soni
Keyword(s):  
Raman Spectroscopy ◽  
Surface Enhanced Raman Spectroscopy ◽  
Excitation Wavelength ◽  
Rhodium Nanoparticles ◽  
Highly Sensitive ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
532 Nm

DUV-UV (266 nm), UV (325 nm) and visible (532 nm) excitation-wavelength-dependent SERS investigation of adenine molecules on rhodium nanoparticles.

Raman spectra of twisted bilayer graphene close to the magic angle

2D Materials ◽  
2022 ◽  
Author(s):  
Tiago Campolina Barbosa ◽  
Andreij C. Gadelha ◽  
Douglas A. A. Ohlberg ◽  
Kenji Watanabe ◽  
Takashi Taniguchi ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Laser Excitation ◽  
Bilayer Graphene ◽  
Geometrical Model ◽  
Excitation Wavelength ◽  
Magic Angle ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Excitation Laser ◽  
Twisted Bilayer Graphene

Abstract In this work, we study the Raman spectra of twisted bilayer graphene samples as a function of their twist-angles (θ), ranging from 0.03º to 3.40º, where local θ are determined by analysis of their associated moiré superlattices, as imaged by scanning microwave impedance microscopy. Three standard excitation laser lines are used (457, 532, and 633 nm wavelengths), and the main Raman active graphene bands (G and 2D) are considered. Our results reveal that electron-phonon interaction influences the G band's linewidth close to the magic angle regardless of laser excitation wavelength. Also, the 2D band lineshape in the θ < 1º regime is dictated by crystal lattice and depends on both the Bernal (AB and BA) stacking bilayer graphene and strain soliton regions (SP) [1]. We propose a geometrical model to explain the 2D lineshape variations, and from it, we estimate the SP width when moving towards the magic angle.

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