Laser-induced breakdown spectroscopy experimentation and applications

This is an era of rapid production and fast growth. Reliable and fast analytical testing techniques are an essential part of manufacturing industries and testing and certifying authorities. Laser-Induced Breakdown Spectroscopy (LIBS) is one of the highly potential techniques to compete in this competitive arena for rapid elemental analysis which can be further used for real-time composition monitoring in the production line, post-production inspection, scrap sorting and even for classification of biological samples. In addition, remote and stand-off modes of operation increase the application potential of LIBS by many folds. It can be deployed in physically inaccessible or potentially unsafe areas. Compact LIBS systems have made its portability possible which implies ease of in-situ deployment

Measurement of optical path difference of white light fibre interferometer using peak tracking method

The major emphasis in the field of interferometry is the determination of optical path difference of the interferometer. This study seeks to evaluate the peak tracking method for computing the optical path difference o f the Mach-Zehnder fibre interferometer

Diagnostics of laser induced graphite plasma under various pressures of air, helium and argon

Laser induced plasma provides information about the elemental composition of sample surface and through spectroscopy vital information about plasma dynamics can be obtained. In this paper we present the diagnostics of laser induced plasma at various pressures of Air, Helium and Argon gases. Graphite sample was ablated with Q-smart 850 laser while spectra were captured Plasma parameters have been calculated by using well known methods based on Saha and Boltzmann equations. Plasma temperature was calculated relative intensity of ionic carbon lines CII 251.21 nm and CII 426.73 nm while the electron density was determined by using spectroscopic information of CI 247.85 nm and CII 426.73 nm emission lines in Saha equation. Plasma temperature and electron density were found to be dependent upon nature and pressure of the ambient atmosphere. Higher temperatures and electron densities were obtained in the presence of Air as ambient environment that is attributed to electrical and physical properties of the Air. Keeping into consideration the plasma expansion in various environments the selection of a suitable ambient pressure can be made on the basis of spectral diagnostics of plasma for a particular laser energy to obtain desirable plasma temperature and electron density suited for certain applications

Response of FBG-bonded plastic plate at different locations of applied stress

Fiber Bragg Grating sensing (FBG) has been intensively studied in the application of smart structures because of its immense advantages offered over those of the conventional sensors. In these researches unique characteristics of FBG, like its high sensitive resonance frequency spectrum and its resonant behavior were reported when FBG was coated by a ring-shaped material and used as an underwater acoustic sensor. In this study, the response of a FBG-bonded plastic plate at different locations of applied stress is demonstrated. The sensing element utilized for this purpose is a 10 mm FBG sensor bonded onto the surface of a plastic plate. Results of reflection spectrum showed that the output power increased randomly when the location of applied stress approached the location of FBG. This was assured from the increment of the area of reflection spectrum. The random increase in the output voltage was attributed to the insufficient stiffness of the plastic ruler, suggesting the implement of graphene plate instead of plastic ruler and increasing the grating length of FBG. The results showed an increase in the output power as detected by the photodiode. Consequently, a clear correlation between the optical and electrical outputs was observed

Surface plasmon resonance sensor of silver film based on Kretchmann configuration

Performance of a surface plasmon resonance (SPR) sensor based on Kretchmann configuration for silver (Ag) film is evaluated via theoretical simulation. The film thickness and incident angle are varied to obtain the SPR wavelength in the range of 500-550 nm. Shift of SPR wavelength with refractive index of the dielectric defines the sensitivity whereas the resolution is obtained from the ratio of the instrumental resolution to the sensitivity. The SPR sensor shows increasing sensitivity for thicker film however the absorption magnitudes of such films are high and unfavourable for data acquisition. Film thickness of 45 nm and 50 nm which has good sensitivity and resolution with high absorbance magnitude of the SPR wavelength is the best thickness to be employed for sensing purpose

Detection of calcium in rice using laser-induced breakdown spectroscopy (LIBS)

Laser-Induced Breakdown Spectroscopy (LIBS) is a very reliable technique for both qualitative and quantitative analyses. Detection of elements composition is important to help consumer choose the right variety of rice. In this paper, an ungated LIBS system was used to detect calcium in rice. An experimental setup was designed using Nd:YAG laser operating at 1064 nm (60 mJ per pulse) and a spectrometer connected to a fiber optic in order to collect the atomic emission which is displayed on a computer. Twelve samples of rice were purchased from local market which offered differences with regard to their rice varieties, grain size and polishing rate. The calcium concentration of each sample was initially evaluated by using Atomic Absorption Spectroscopy (AAS) after acid digestion. Pellets of approximately 5 mm thick and 40 mm diameter were prepared by transferring 10 g of ground rice sample to a 40 mm die set and applying 40 MPa. For the LIBS analysis, Nd:YAG laser was used to ablate the surface of each pellets. Fifty spectra from different spots of the pellets were collected by the spectrometer from each sample. The spectra were then averaged and analyzed using OriginPro 8.5 for baseline removal and peak findings. Two calcium (Calcium II) lines with high intensity were observed at the wavelength of 393.37 nm and 396.85 nm. The study shows that LIBS can be an excellent tool for detecting calcium in rice

Double-brillouin-frequency spaced multiwavelength fiber laser using high resolution OSA

We successfully demonstrate a double-frequency spaced multiwavelength Brillouin fiber laser (MWBFL) using a dispersion shifetd fiber (DSF) as the nonlinear medium. The spectrum of the MWBFL is observed by using a standard optical specrumanalyser (OSA) with a resolution of 0.02 nm. for comparison purpose, further verifcation of the double spacing spectrum is done by observing the spectrum using a high resolution OSA with the resolution of 0.16 pm. We realized that even thespacing between two consecutive of stokes is double-frequency shifted,however there are still hidden stokes wavelength spacing of 0.08 nm.From this observation it can be deduced that even-though the above described ring configuration should by all means only allow for double-spaced Stokes outputs, in reality both even and odd Stokes lines propagate in both directions in the laser cavity

Volatolomics combined terahertz time - domain spectral analyses of colon cancer in vitro

Terahertz time-domain spectroscopy (THz-TDS) offers a great advantage for the analysis of biological samples. In this study, we combined THz-TDS with volatolomics analysis and analyzed 2 colon cell lines via in vitro settings. The release of volatile organic compounds (VOCs) was measured from the normal colon (CCD112CoN) and cancer colon (COLO320DM) cell lines which were grown in sealed flasks. Data validation were carried out with principal component analysis (PCA) and partial least square (PLS) scores while the chemometric analyses were performed using Camo Unscrambler X software. In-depth THz-TDS spectral analysis of the cancer colon (COLO320DM) cell line shows significant traces of benzamide gas when validated using gas chromatography-mass selective detection (GC-MSD) system. This preliminary data shows the potential use of identification and quantification of benzamide compound in the cancer colon cells and this could provide useful insight towards cancer drug design and therapy

Single mode EDF fiber laser using an ultra-narrow bandwidth tunable optical filter

Single longitudinal mode (SLM) erbium-doped fiber (EDF) laser operation using a commercialized ultra-narrow bandwidth optical filter has been demonstrated. A 2-m long EDF with an absorption coefficient of 24 dB m-1 at the pump wavelength is used as gain medium. The ultra-narrow tunable filter is used for selection of a single longitudinal mode from the available spectrum of multiple modes, which originally exist in the FBG's reflection spectrum. Our approach provides a relatively simple and direct method for realization of SLM operation. A high-resolution optical spectral analyser with a resolution of 0.16 pm isused to observe the output spectrum. To verify the SLM operation, the delayed self-heterodyne methodis used, giving a measured laser linewidth of 61.5 kHz

Tunable single stokes extraction from 20 GHz Brillouin fiber laser using ultranarrow bandwidth optical filter

The individual extraction of a Brillouin Stokes line from a 20 GHz comb generated from the compact configuration of a multiwavelength Brillouin fiber ring laser configuration has been achieved using an ultranarrow bandwidth (UNB) optical filter. The narrowest bandwidth transmission of a UNB optical filter that is 50 pm is used in order to get particular Stokes. The Stokes filtered is in the wavelength range of 1549.768–1551.016 nm. High SNR within the range of 54.97–11.73 dB with almost nil peak power loss being obtained was monitored by a 0.16 pm optical spectrum analyzer, giving convincing results. Relatively, the proposed configuration could provide wide tunability and narrow selection of the Brillouin Stokes. © 2014 Optical Society of Americ