scholarly journals Fast Gating for Raman Spectroscopy

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2579
Author(s):  
Andrea Chiuri ◽  
Federico Angelini
Keyword(s):  
Raman Spectroscopy ◽  
Time Domain ◽  
Single Photon ◽  
Raman Signal ◽  
Fluorescence Signal ◽  
Fast Gating ◽  
Resonant Raman ◽  
Set Up ◽  
The Time Domain ◽  
Single Photon Avalanche Photodiodes

Fast gating in Raman spectroscopy is used to reject the fluorescence contribution from the sample and/or the substrate. Several techniques have been set up in the last few decades aiming either to enhance the Raman signal (CARS, SERS or Resonant Raman scattering) or to cancel out the fluorescence contribution (SERDS), and a number of reviews have already been published on these sub-topics. However, for many reasons it is sometimes necessary to reject fluorescence in traditional Raman spectroscopy, and in the last few decades a variety of papers dealt with this issue, which is still challenging due to the time scales at stake (down to picoseconds). Fast gating (<1 ns) in the time domain allows one to cut off part of the fluorescence signal and retrieve the best Raman signal, depending on the fluorescence lifetime of the sample and laser pulse duration. In particular, three different techniques have been developed to accomplish this task: optical Kerr cells, intensified Charge Coupling Devices and systems based on Single Photon Avalanche Photodiodes. The utility of time domain fast gating will be discussed, and In this work, the utility of time domain fast gating is discussed, as well as the performances of the mentioned techniques as reported in literature.

scholarly journals Laser Raman Spectroscopy with Different Excitation Sources and Extension to Surface Enhanced Raman Spectroscopy

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Md. Wahadoszamen ◽  
Arifur Rahaman ◽  
Nabil Md. Rakinul Hoque ◽  
Aminul I Talukder ◽  
Kazi Monowar Abedin ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Silver Nanoparticles ◽  
Rhodamine 6G ◽  
Detection Efficiency ◽  
Colloidal Suspension ◽  
Surface Enhanced Raman Spectroscopy ◽  
Laser Raman Spectroscopy ◽  
Raman Signal ◽  
Fluorescence Signal ◽  
Present System

A dispersive Raman spectrometer was used with three different excitation sources (Argon-ion, He-Ne, and Diode lasers operating at 514.5 nm, 633 nm, and 782 nm, resp.). The system was employed to a variety of Raman active compounds. Many of the compounds exhibit very strong fluorescence while being excited with a laser emitting at UV-VIS region, hereby imposing severe limitation to the detection efficiency of the particular Raman system. The Raman system with variable excitation laser sources provided us with a desired flexibility toward the suppression of unwanted fluorescence signal. With this Raman system, we could detect and specify the different vibrational modes of various hazardous organic compounds and some typical dyes (both fluorescent and nonfluorescent). We then compared those results with the ones reported in literature and found the deviation within the range of ±2 cm−1, which indicates reasonable accuracy and usability of the Raman system. Then, the surface enhancement technique of Raman spectrum was employed to the present system. To this end, we used chemically prepared colloidal suspension of silver nanoparticles as substrate and Rhodamine 6G as probe. We could observe significant enhancement of Raman signal from Rhodamine 6G using the colloidal solution of silver nanoparticles the average magnitude of which is estimated to be 103.

scholarly journals Squeezing-enhanced Raman spectroscopy

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Yoad Michael ◽  
Leon Bello ◽  
Michael Rosenbluh ◽  
Avi Pe’er
Keyword(s):  
Raman Spectroscopy ◽  
Shot Noise ◽  
Raman Signal ◽  
Background Suppression ◽  
Destructive Interference ◽  
Parametric Amplifiers ◽  
Two Phase ◽  
Resonant Raman ◽  
Raman Response ◽  
Anti Stokes

Abstract The sensitivity of classical Raman spectroscopy methods, such as coherent anti-stokes Raman spectroscopy (CARS) or stimulated Raman spectroscopy (SRS), is ultimately limited by shot-noise from the stimulating fields. We present the complete theoretical analysis of a squeezing-enhanced version of Raman spectroscopy that overcomes the shot-noise limit of sensitivity with enhancement of the Raman signal and inherent background suppression, while remaining fully compatible with standard Raman spectroscopy methods. By incorporating the Raman sample between two phase-sensitive parametric amplifiers that squeeze the light along orthogonal quadrature axes, the typical intensity measurement of the Raman response is converted into a quantum-limited, super-sensitive estimation of phase. The resonant Raman response in the sample induces a phase shift to signal-idler frequency-pairs within the fingerprint spectrum of the molecule, resulting in amplification of the resonant Raman signal by the squeezing factor of the parametric amplifiers, whereas the non-resonant background is annihilated by destructive interference. Seeding the interferometer with classical coherent light stimulates the Raman signal further without increasing the background, effectively forming squeezing-enhanced versions of CARS and SRS, where the quantum enhancement is achieved on top of the classical stimulation.

scholarly journals Ultra Wideband Coplanar Waveguide Antenna with an Improved Gain using a Frequency Selective Surfaces (FSS)

2019 ◽  
Vol 8 (9S) ◽  
pp. 145-149
Keyword(s):  
Time Domain ◽  
Coplanar Waveguide ◽  
Unit Cell ◽  
Ultra Wideband ◽  
Frequency Range ◽  
Rectangular Slot ◽  
Improved Performance ◽  
Set Up ◽  
The Time Domain ◽  
Uwb Applications

In this article, an ultra-wideband FSS reflector has been proposed to enhance the gain of a CPW antenna for UWB applications. A CPW fed antenna having dimensions of 38mm×38mm×1.605mm and FSS unit cell having dimensions 14mm × 14mm × 1.605 mm are presented in the paper. A rectangular slot and stubs are interleaved at the outer edges of the patch for achieving desired characteristics of an ultra-wideband for the frequency range of 3.39 GHz to 12.9 GHz. Simulation results carried out using the CST microwave 2016 version in the time domain are presented for the proposed antenna. An FSS unit cell designed and simulated using periodic boundary conditions and floquet ports is presented. The combined setup of an array of FSS reflector behind the antenna has been simulated in the time domain. This set up shows an improved performance in terms of antenna’s gain. A maximum and minimum gain of 8.14 dB and 4.98 dB has been observed with the presence of FSS reflector behind the coplanar waveguide antenna. A significant improvement of 2.9 dB has been observed over the entire band of antenna’s operation

Measurements of Shielding Effectiveness of Textile Materials Containing Metal by the Free-Space Transmission Technique with Data Processing in the Time Domain

2013 ◽  
Vol 20 (2) ◽  
pp. 217-228 ◽  
Author(s):  
Nadezhda Dvurechenskaya ◽  
Pawe R. Bajurko ◽  
Ryszard J. Zieliński ◽  
Yevhen Yashchyshyn
Keyword(s):  
Data Processing ◽  
Time Domain ◽  
Free Space ◽  
Coaxial Line ◽  
Shielding Effectiveness ◽  
Experimental Data Processing ◽  
Textile Materials ◽  
Transmission Technique ◽  
Set Up ◽  
The Time Domain

Abstract The results of shielding effectiveness (SE) measurements of textile materials containing metal by the free-space transmission technique (FSTT) in the 1-26.5 GHz frequency range are presented in the paper. It is shown that experimental data processing using time-domain gating (TDG) makes it possible to effectively remove diffracted and reflected components from the desired signal. The comparison with the results obtained by other techniques, namely modified FSTT with TDG and coaxial line probe technique (ASTM D4935-99) is given. The comparison shows that the proposed technique gives more reasonable results while the measurement set-up is simpler in realization.

Modeling and Analysis of the Operational Amplifier with SC Circuit

2014 ◽  
Vol 687-691 ◽  
pp. 3304-3310
Author(s):  
Xing Hua Wang ◽  
Pei Rong Jiang
Keyword(s):  
Charge Transfer ◽  
Time Domain ◽  
Open Loop ◽  
The Other ◽  
Charge Storage ◽  
Phase Margin ◽  
Output Function ◽  
Modeling And Analysis ◽  
Set Up ◽  
The Time Domain

This paper set up two structures model of switched-capacitor circuit based on second-order output settling, one type is charge transfer, the other is capacitance overturn. According to charge conservation when in charge storage and charge transfer process, the transfer function derived. By analyzing the time-domain solution in the form of output function, we find out the factors which influence on the rate of SC. In order to achieve the fastest settling time, the phase margin of open-loop amplifier is 63.4° in charge transfer by calculated, while in capacitance overturn is 76°.

scholarly journals Simulation of Partial Discharge Induced EM Waves Using FDTD Method—A Parametric Study

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3364 ◽  
Author(s):  
Alaa Loubani ◽  
Noureddine Harid ◽  
Huw Griffiths ◽  
Braham Barkat
Keyword(s):  
Time Domain ◽  
Parametric Study ◽  
Fdtd Method ◽  
Insulation Material ◽  
Frequency Content ◽  
Lateral Direction ◽  
Close Proximity ◽  
Set Up ◽  
The Time Domain ◽  
Uhf Antenna

This paper reports the results of a parametric study on the characteristics of electromagnetic (EM) waves propagated due to surface- and cavity-type partial discharges (PD) in materials using the finite-difference time domain (FDTD) method. First, the EM waves emitted by such discharges in material samples were measured using a broadband aperture antenna. The measurements showed that the frequency range of the measured signals lay within the ultra-high frequency (UHF) range, suggesting that by carefully choosing the UHF antenna characteristics and its location it might be possible to apply this method to characterize the PD-emitted waves; and hence, to potentially use it to detect and monitor PD defects. In this context, the FDTD simulations were used here to simulate the experimental set-up and examine the propagation characteristics of EM waves emitted by such discharges under uniform and non-uniform test electrode configurations. Using an approximation of the exciting PD current pulses, the electromagnetic field components and the voltage signals captured on a simulated monopole sensor were computed in the time domain at various locations. To explore the limits of the application of the UHF method for detecting these PD types, a parametric study was carried out to clarify how the captured signals are influenced by the PD intensity, the frequency content of the exciting PD pulse, the type of insulation material, the dimensions and the position of the UHF antenna. One of the challenges that needs further investigation is the accurate simulation of the actual PD current pulse produced by such discharges, and hence its frequency content, as there is limited or no measured data available. The results showed that while the amplitude of the captured EM signals increase with the PD intensity, no appreciable signal is detected when the PD pulse width is higher than about 4ns, which may not occur often in unbounded air insulated systems. Equally important is the location and orientation of the UHF sensor—the results showed improved sensitivity when the sensor is vertically polarized and placed in close proximity in the lateral direction with reference to the discharge path.

scholarly journals Time-Gated Single-Photon Detection in Time-Domain Diffuse Optics: A Review

2020 ◽  
Vol 10 (3) ◽  
pp. 1101 ◽  
Author(s):  
Alberto Dalla Mora ◽  
Laura Di Sieno ◽  
Rebecca Re ◽  
Antonio Pifferi ◽  
Davide Contini
Keyword(s):  
Time Domain ◽  
Dynamic Range ◽  
Single Photon ◽  
Signal To Noise Ratio ◽  
Single Photon Detection ◽  
Photon Detection ◽  
Ratio Measurement ◽  
Diffuse Optics ◽  
Detection Strategy ◽  
The Time Domain

This work reviews physical concepts, technologies and applications of time-domain diffuse optics based on time-gated single-photon detection. This particular photon detection strategy is of the utmost importance in the diffuse optics field as it unleashes the full power of the time-domain approach by maximizing performances in terms of contrast produced by a localized perturbation inside the scattering medium, signal-to-noise ratio, measurement time and dynamic range, penetration depth and spatial resolution. The review covers 15 years of theoretical studies, technological progresses, proof of concepts and design of laboratory systems based on time-gated single-photon detection with also few hints on other fields where the time-gated detection strategy produced and will produce further impact.

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