Spectrochemical Analysis of Liquids Using Laser-Induced Plasma Emissions: Effects of Laser Wavelength

The plasma plume emissions produced by pulsed (∼ 10 ns) laser ablation of liquid jets were monitored for spectrochemical analysis. Laser wavelengths at 532 and 193 nm were used, and sodium was the test analyte. As expected, the 532-nm laser pulse produced very intense plasma continuum emissions that masked the sodium signal for the first hundred nanoseconds, especially near the bright core of the vapor plume. Neither time-gating nor spatial masking could significantly improve the single-shot signal-to-noise ratio, since the transient nature of the emissions placed stringent demands on timing precision while the small size of the plume required accurate mask positioning—both antithetical to the inherent instability of jet ablation. In sharp contrast, the 193-nm laser pulse produced relatively dim plasma flash but intense sodium emissions, rendering it ideal for analytical applications.

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Spectrochemical Analysis of Liquids Using Laser-Induced Plasma Emissions: Effects of Laser Wavelength on Plasma Properties

Applied Spectroscopy ◽

10.1366/0003702971941638 ◽

1997 ◽

Vol 51 (7) ◽

pp. 976-983 ◽

Cited By ~ 71

Author(s):

C. W. Ng ◽

W. F. Ho ◽

N. H. Cheung

Keyword(s):

Laser Ablation ◽

Electron Density ◽

Laser Wavelength ◽

Plasma Properties ◽

Sodium Potassium ◽

Thermally Induced ◽

Plasma Plumes ◽

Plume Temperature ◽

193 Nm ◽

532 Nm

We spectroscopically determined the temperature and electron density of the plasma plumes produced by pulsed-laser ablation of aqueous solutions containing sodium, lithium, and rubidium. With the use of a Nd:YAG laser at 532 nm and fluence of 3 J/cm2, the plasma produced was hot (low eV range) and extensively ionized, with electron density in the 1018 cm−3 range. Analyte line signals were initially masked by intense plasma continuum emissions and would only emerge briefly above the background when the plume temperature dropped below 1 eV during the course of its very rapid cooling. Since ionization was thermally induced, the intense plasma flash was inevitable. In contrast, 193-nm laser ablation at similar fluence generated plasmas of much lower (<1 eV) temperature but comparable electron density. Plasma continuum emissions were relatively weak, and the signal-to-background ratio was a thousand times better. Consequently, this “cold” plasma was ideal for sampling biologically important elements such as sodium, potassium, and calcium.

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Linear and Nonlinear Optical Properties of Natural Dyes Freestanding Films and Application in Optical Limiting

10.32792/utq/utjsci/vol7/2/30 ◽

2020 ◽

pp. 139-143

Keyword(s):

Absorption Coefficient ◽

Water Solution ◽

Optical Limiting ◽

Refraction Index ◽

Laser Wavelength ◽

Solid State Laser ◽

Natural Dyes ◽

Linear And Nonlinear ◽

532 Nm ◽

Absorbance Spectra

Natural dyes were followed and prepared from a pomegranate, purple carrot, and eggplant peel. The absorbance spectra was measured in the wavelength range 300-800 nm. The linear properties measurements of the prepared natural dye freestanding films were determined include absorption coefficient (α0), extinction coefficient (κ), and linear refraction index (n). The nonlinear refractive index n2 and nonlinear absorption coefficient β2 of the natural dyes in the water solution were measured by the optical z-scan technique under a pumped solid state laser at a laser wavelength of 532 nm. The results indicated that the pomegranate dye can be promising candidates for optical limiting applications with significantly low optical limiting of 3.5 mW.

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Femtosecond Pulsed Laser-Induced Micromachining of Difficult-to-Machine Materials: Diamond a Case Study

10.1115/imece2000-1905 ◽

2000 ◽

Author(s):

A. P. Malshe ◽

A. M. Ozkan ◽

T. A. Railkar ◽

K. P. Adhi ◽

W. D. Brown ◽

...

Keyword(s):

Raman Spectroscopy ◽

Excimer Laser ◽

Etching Rate ◽

Polycrystalline Diamond ◽

Single Pulse ◽

Laser Wavelength ◽

Diamond Surface ◽

Single Shot ◽

Micro Machining ◽

3 Dimensional

Abstract Meso and micro scale machining is an important and emerging area of research. Various non-traditional and novel tools are being explored for meso and micro machining of non-silicon materials. In this paper, we report etching, micro machining and related phenomena of commercially available single and polycrystalline diamond using a femtosecond pulsed excimer laser (λ = 248 nm, tp ∼ 380 fs). Surface modifications due to single pulse and multiple pulse irradiation of diamond samples, at different energy densities, have been analyzed using Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Etching rate of single crystal type IIA diamond by femtosecond pulsed excimer laser is also studied. Raman spectroscopy study of the single shot irradiation of diamond with a femto second laser shows the formation of a non-diamond disordered (sp2 bonded) phase on the surface. However, subsequent micro machining of this non-diamond disordered surface, by delivering several shots from the femtosecond laser, results in the removal of the non-diamond disordered layer and the restoration of the diamond surface. It is experimentally shown that the periodicity of the 2-dimensional corrugations written on diamond surface is shorter than the laser wavelength used. 3-dimensional writing on diamond globules during laser etching is also discussed. Further, micro machining of diamond tips is shown to be precise, and without mechanical and chemical damages. Femto second laser is demonstrated as a next-generation tool for mechanical and chemical damage free precision micro machining of the hardest material, diamond.

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Clinical impact of ultra-high b-value (3000 s/mm2) diffusion-weighted magnetic resonance imaging in prostate cancer at 3T: comparison with b-value of 2000 s/mm2

British Journal of Radiology ◽

10.1259/bjr.20210465 ◽

2021 ◽

pp. 20210465

Author(s):

Tsutomu Tamada ◽

Ayumu Kido ◽

Yu Ueda ◽

Mitsuru Takeuchi ◽

Takeshi Fukunaga ◽

...

Keyword(s):

Prostate Cancer ◽

Diagnostic Performance ◽

Signal To Noise Ratio ◽

B Value ◽

Single Shot ◽

Signal To Noise ◽

High B Value ◽

Diffusion Weighted ◽

Significant Difference ◽

Noise Ratio

Objective: High b-value diffusion-weighted imaging (hDWI) with a b-value of 2000 s/mm2 provides insufficient image contrast between benign and malignant tissues and an overlap of apparent diffusion coefficient (ADC) between Gleason grades (GG) in prostate cancer (PC). We compared image quality, PC detectability, and discrimination ability for PC aggressiveness between ultra-high b-value DWI (uhDWI) of 3000 s/mm2 and hDWI. Methods: The subjects were 49 patients with PC who underwent 3T multiparametric MRI. Single-shot echo-planar DWI was acquired with b-values of 0, 2000, and 3000 s/mm2. Anatomical distortion of prostate (AD), signal intensity of benign prostate (PSI), and lesion conspicuity score (LCS) were assessed using a 4-point scale; and signal-to-noise ratio, contrast-to-noise ratio, and mean ADC (×10–3 mm2/s) of lesion (lADC) and surrounding benign region (bADC) were measured. Results: PSI was significantly lower in uhDWI than in hDWI (p < 0.001). AD, LCS, signal-to-noise ratio, and contrast-to-noise ratio were comparable between uhDWI and hDWI (all p > 0.05). In contrast, lADC was significantly lower than bADC in both uhDWI and hDWI (both p < 0.001). In comparison of lADC between tumors of ≤GG2 and those of ≥GG3, both uhDWI and hDWI showed significant difference (p = 0.007 and p = 0.021, respectively). AUC for separating tumors of ≤GG2 from those of ≥GG3 was 0.731 in hDWI and 0.699 in uhDWI (p = 0.161). Conclusion: uhDWI suppressed background signal better than hDWI, but did not contribute to increased diagnostic performance in PC. Advances in knowledge: Compared with hDWI, uhDWI could not contribute to increased diagnostic performance in PC.

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A New Method Using Chirp-Matching OPCPA Scheme for Improving Signal-to-Noise Ratio of Ultrashort Laser Pulse

Acta Optica Sinica ◽

10.3788/aos201131.0719001 ◽

2011 ◽

Vol 31 (7) ◽

pp. 0719001

Author(s):

曾曙光 Zeng Shuguang ◽

张彬 Zhang Bin ◽

李现华 Li Xianhua ◽

孙年春 Sun Nianchun ◽

隋展 Sui Zhan

Keyword(s):

Laser Pulse ◽

Ultrashort Laser Pulse ◽

Signal To Noise Ratio ◽

New Method ◽

Signal To Noise ◽

Noise Ratio ◽

Ultrashort Laser

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Improving signal-to-noise ratio of chirped laser pulse using Mach-Zehnder interferometer

High Power Laser and Particle Beams ◽

10.3788/hplpb20132511.2788 ◽

2013 ◽

Vol 25 (11) ◽

pp. 2788-2792

Author(s):

曾冰 Zeng Bing ◽

叶荣 Ye Rong ◽

张彬 Zhang Bin ◽

孙年春 Sun Nianchun ◽

隋展 Sui Zhan

Keyword(s):

Laser Pulse ◽

Signal To Noise Ratio ◽

Zehnder Interferometer ◽

Signal To Noise ◽

Noise Ratio ◽

Chirped Laser Pulse ◽

Mach Zehnder Interferometer

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CALIPSO lidar calibration at 1064 nm: version 4 algorithm

Atmospheric Measurement Techniques ◽

10.5194/amt-12-51-2019 ◽

2019 ◽

Vol 12 (1) ◽

pp. 51-82 ◽

Cited By ~ 19

Author(s):

Mark Vaughan ◽

Anne Garnier ◽

Damien Josset ◽

Melody Avery ◽

Kam-Pui Lee ◽

...

Keyword(s):

Molecular Model ◽

Signal To Noise Ratio ◽

High Spectral Resolution ◽

Orthogonal Polarization ◽

Radiometric Calibration ◽

Calibration Target ◽

Full Account ◽

High Spectral Resolution Lidar ◽

532 Nm ◽

Calibration Coefficients

Abstract. Radiometric calibration of space-based elastic backscatter lidars is accomplished by comparing the measured backscatter signals to theoretically expected signals computed for some well-characterized calibration target. For any given system and wavelength, the choice of calibration target is dictated by several considerations, including signal-to-noise ratio (SNR) and target availability. This paper describes the newly implemented procedures used to calibrate the 1064 nm measurements acquired by CALIOP (i.e., the Cloud-Aerosol Lidar with Orthogonal Polarization), the two-wavelength (532 and 1064 nm) elastic backscatter lidar currently flying on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission. CALIOP's 532 nm channel is accurately calibrated by normalizing the molecular backscatter from the uppermost aerosol-free altitudes of the CALIOP measurement region to molecular model data obtained from NASA's Global Modeling and Assimilation Office. However, because CALIOP's SNR for molecular backscatter measurements is prohibitively lower at 1064 nm than at 532 nm, the direct high-altitude molecular normalization method is not a viable option at 1064 nm. Instead, CALIOP's 1064 nm channel is calibrated relative to the 532 nm channel using the backscatter from a carefully selected subset of cirrus cloud measurements. In this paper we deliver a full account of the revised 1064 nm calibration algorithms implemented for the version 4.1 (V4) release of the CALIPSO lidar data products, with particular emphases on the physical basis for the selection of “calibration quality” cirrus clouds and on the new averaging scheme required to characterize intra-orbit calibration variability. The V4 procedures introduce latitudinally varying changes in the 1064 nm calibration coefficients of 25 % or more, relative to previous data releases, and are shown to substantially improve the accuracy of the V4 1064 nm attenuated backscatter coefficients. By evaluating calibration coefficients derived using both water clouds and ocean surfaces as alternate calibration targets, and through comparisons to independent, collocated measurements made by airborne high spectral resolution lidar, we conclude that the CALIOP V4 1064 nm calibration coefficients are accurate to within 3 %.

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