Now showing 1 - 10 of 182
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    Pulsed Laser Assisted Micro-Scribing of Metal thin Films in Air and Underwater Using UV, Visible and Near-IR Wavelengths
    (01-01-2016)
    Nammi, Srinagalakshmi
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    Balaganesan, G.
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    Mathur, Anil C.
    A comparative study has been made for micro-scribing of copper and aluminum thin films in air and underwater using 355nm, 532nm and 1064nm wavelengths of a Q-switched Nd3+: YAG laser with 6ns pulse duration. For aluminum in air medium, the channel depth obtained is high for 355nm wavelength, whereas for copper coated on a polyimide substrate, 532nm wavelengths produced higher depth. In underwater scribing, with increase in the pulsed laser energy, the depth of micro channel was increased and remained unchanged at higher energy. The influence of beam profile on the micro channel cross-section has also been discussed. Further, theoretical modeling of the laser-material interaction in air and underwater ambience conditions to estimate the recession rate has been discussed by incorporating the laser ablation temperature measured using the laser induced breakdown spectroscopy technique.
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    Supercontinuum Laser Based Photoacoustic Approach for Acetylene Gas Sensing
    (02-07-2018)
    Selvaraj, Ramya
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    A broadband photoacoustic gas sensor with solid etalon using supercontinuum laser for acetylene monitoring was characterized. The acetylene concentration was determined to be 330 pptv at a data acquisition time of 10 ms.
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    Mixed gas sensing system based on super-luminescent diode coupled with a fabry-perot etalon
    (01-12-2011)
    Divya, K.
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    Mixed gas sensing based on a broad-band super-luminescent diode (1535 nm) coupled with an external Fabry-Perot etalon is proposed. The wavelength tuning by tilting the etalon will provide selective gas sensing by absorption spectroscopy technique. © OSA/CLEO 2011.
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    Simulation of a Non-Contact Triple-Wavelength Reflectance Pulse Oximeter to Measure Oxygen and Carbon Monoxide Saturations
    (01-01-2023)
    Veerabathraswamy, Swathi
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    John, Pauline
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    This paper relates to the design of a novel reflectance pulse oximeter, which can measure not only the arterial oxygen saturation, but also that of carbon monoxide, in a non-contact manner. Such an instrument is especially relevant in the monitoring of patients who have a history of smoking, or those who have been exposed to carbon monoxide poisoning, such as from fires. The remote manner of measurement ensures that the risk of contact contamination is eliminated, and that the instrument can be used on infants as well, especially those born prematurely and having sensitive skin. A novel algorithm was devised which uses light sources of three different wavelengths to calculate the above mentioned saturations. A thorough sensitivity analysis was performed to determine the most suitable wavelengths for the purpose, which were determined to be 660 nm, 640 nm, and 940 nm. A system was designed to leverage the above mentioned algorithm, and the same was simulated using Simulink. The simulation gave satisfactory results, with maximum errors in calculation of oxygen and carbon monoxide saturations being 0.36% and 0.66%, respectively. These results are discussed along with measures that can be used to improve accuracy.
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    LIBS technique combined with blow gas and vacuum suction to remove particle cloud and enhance emission intensity during characterization of powder samples
    (01-07-2021)
    Rajavelu, Hemalaxmi
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    The present study reports developing a bench-top Laser-Induced Breakdown Spectroscopy (LIBS) set up for the online analysis of powder samples without sample preparation. The powder particle blow-off during pulsed laser ablation was mitigated by adding a blow gas (an inert gas blown across the ablation surface) and a suction unit (for extraction of the blow gas and blown-off particle cloud) to the existing LIBS setup. The influence of a blow-gas combined with a suction unit on LIBS emission intensity from coal powder and flyash particles is studied in the present work. The effect of the blow gas flow rate and the suction pressure was studied on the LI-BS emission intensity and removal of the laser blown-off particle cloud. The combination gas flow at 2 lpm (liter per minute) flow rate and suction at 925 mbar (absolute) show an increase in the LIBS emission intensity and effective particle removal. The ratio of LIBS emission intensity of the powder sample and solid-target (pellet) sample improved from 0.25 without the Ar gas flow and the suction unit to 0.85, which is by a factor of 3.4 times with the proposed approach.
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    Annealing and texturing of a-Si film using Nd3+:YAG laser with Gaussian and flat-top beam profiles
    (01-12-2010)
    Palani, I. A.
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    Rajiv, G.
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    Singaperumal, M.
    An application of a pulsed, solid-state laser with a Gaussian and flat-top beam profiles is considered for annealing and nano-texturing of amorphous-silicon (a-Si) films. Investigations are performed with the third harmonics (355 nm) Nd3+:YAG laser. To crystallize and subsequently induce texture, a-Si films are treated by spatial-overlapping of the laser spots on the surface by 90% of its size. The generation of texturization mechanism in laser assisted annealing and texturing is theoretically investigated and experimentally analyzed. ©2010 IEEE.
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    Single laser based pump-probe technique to study plasma shielding during nanosecond laser ablation of copper thin films
    (11-08-2017)
    Nammi, Srinagalakshmi
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    Gurusamy, Balaganesan
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    Mathur, Anil C.
    A plasma shielding phenomenon and its influence on micromachining is studied experimentally and theoretically for laser wavelengths of 355 nm, 532 nm and 1064 nm. A time resolved pump-probe technique is proposed and demonstrated by splitting a single nanosecond Nd3+:YAG laser into an ablation laser (pump laser) and a probe laser to understand the influence of plasma shielding on laser ablation of copper (Cu) clad on polyimide thin films. The proposed nanosecond pump-probe technique allows simultaneous measurement of the absorption characteristics of plasma produced during Cu film ablation by the pump laser. Experimental measurements of the probe intensity distinctly show that the absorption by the ablated plume increases with increase in the pump intensity, as a result of plasma shielding. Theoretical estimation of the intensity of the transmitted pump beam based on the thermo-temporal modeling is in qualitative agreement with the pump-probe based experimental measurements. The theoretical estimate of the depth attained for a single pulse with high pump intensity value on a Cu thin film is limited by the plasma shielding of the incident laser beam, similar to that observed experimentally. Further, the depth of micro-channels produced shows a similar trend for all three wavelengths, however, the channel depth achieved is lesser at the wavelength of 1064 nm.
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    Simultaneous measurement of multiple gas species using a nd3+: YAG laser combined with raman scattering
    (01-01-2012)
    Sulochana, K.
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    Eichmann, S. C.
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    Engel, S.
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    Kumaravel, M.
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    Seeger, T.
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    Leipertz, A.
    Coherent anti-Stokes Raman scattering technique combined with a single pulsed Nd3+:YAG laser is proposed and demonstrated for simultaneous measurement of CO2 and CH4. The technique can be used in combustion measurement consisting of gas mixture. © OSA 2012.
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    Fully Room Temperature Bio-Sensing using Active Microdisk Fabricated by Ink-Jet Printing Method
    (01-05-2020)
    Nasir, Abdul
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    Mikami, Yuya
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    Takagishi, Taku
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    Yatabe, Rui
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    Yoshioka, Hiroaki
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    Oki, Yuji
    Fluorinated hyper branched polymer based active microdisk was fabricated by ink-jet printing method. The carboxyl functional group of the polymer was used for the biotinylation of microdisk and then adsorption characteristics of avidin were evaluated.
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    Influence of pulsed Nd3+: YAG laser beam profile and wavelength on micro-scribing of copper and aluminum thin films
    (01-01-2015)
    Nammi, Srinagalakshmi
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    Gupta, Sanjay
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    Mathur, Anil C.
    Evenly spaced conductive grids of copper and aluminum thin films on polyamide substrate are used for parabolic reflector-Antennas, aboard telecommunications satellite. In the present paper, laser micro scribing of thin films using a flat-top and Gaussian laser beam profile are analyzed with 95% overlapping of the diameter of the laser spot. Laser scribing is performed using the Q-switched Nd3+: YAG (355, 532 nm) laser. The influence of laser irradiation and beam shape are experimentally analyzed using non-contact optical profilometer and scanning electron microscope (SEM). Laser scribing using flat-top profile produced near rectangular micro channels in copper thin films. Using Gaussian profile the probability of melting is greater than vaporization as observed using SEM images; this melt pool plays a prominent role in re-solidification at the edges. Depth of the scribe channel is observed to be 20% high for 532 nm wavelength compared to 355 nm wavelength. Effect of different environments such as air, water and vacuum on the channel depth and quality is reported. The response of aluminum and copper for high fluences is also studied. Theoretical modeling of the laser-material interaction using Comsol mulitphysics 4.4 is discussed.