Fiber loop ring down spectroscopy for trace chemical detection

Cengiz, Betül
Fiber loop ring down (FLRD) spectroscopy is a sensitive spectroscopic technique that is based on absorption and it is convenient for trace chemical detection. Different FLRD systems are being improved in order to increase their sensitivity. In FLRD spectroscopy, detection of a sample is done by measuring of a leaking light at each trip within an optical cavity. Intensity of leaking light has an exponential decay where it is reduced by absorption of sample and scattering of light. In this project, two FLRD set-ups at 1535 nm and 808 nm were designed. In both set-ups, optical fiber and optical fiber couplers are used to form a cavity. At 1535 nm, a FLRD set-up is constructed by utilizing a pulsed laser and used for characterization of thin films, various pure liquids and fluorescein solutions. Two different sensor regions are designed with free space collimators and ferrules for the measurement of thin films and liquids, respectively. The future endeavor of the set-up is improvement for reliability and reproducibility of the system. For visible and NIR regions, a fiber coupled laser with four colors as 642 nm, 785 nm, 808 nm and 852 nm laser is used to design of a FLRD set-up. 808 nm laser is selected to build a prototype of the FLRD system. The construction of a closed loop FLRD set-up is completed and the system is characterized. Ultimate aim in our project is to be able to do trace detection at visible and NIR regions where the chemical sensitivity is higher.


Fiber loop ring down spectrometer optical based sensor for trace chemical detection
Yolalmaz, Alim; Esentürk, Okan; Danışman, Mehmet Fatih; Hanifehpour, Farhad (2016-04-11)
Fiber loop ring down (FLRD) is a time domain multi-functional sensing, characterization, detection technique. FLRD technique is used to sense temperature, pressure, strain, biological cells, refractive index, and chemical species. FLRD has high accuracy, high selectivity, ability of remote control and rapid response. In this project, two FLRD spectrometers working at 800 nm (figure 1) and 1535 nm (figure 2) were set up for sensing different chemical analytes like C2H2, CO2, Ar, N2, DMSO, DMF, H2O, C2H6O, C3...
Intracavity gas detection with fiber loop ring down spectroscopy
Yolalmaz, Alim; Hanifehpour Sadroud, Farhad; Danışman, Mehmet Fatih; Esentürk, Okan (Elsevier BV, 2017-8)
In this study, an easy to construct and sensitive intracavity fiber loop ring down spectrometer was built by commercially available basic components and its application on chemical sensing is presented. System performance was investigated by using various acetylene/nitrogen gas mixtures as a function of total pressure (between 25 and 65 psia) in sensing region and a calibration curve is established. The instrument can achieve a limit of detection of 0.1% without a FBG and/or EDFA or a need for a complicated...
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Volkan, Mürvet; Vo-Dinh, T (SAGE Publications, 2000-12-01)
Surface-enhanced Raman spectroscopy (SERS) is used to detect catecholamines-viz., dopamine, norepinephrine, epinine, and isoproterenol-using a new substrate prepared with sol-gel technology. Catecholamines are complexed at the surface by iron(III) ions, which were introduced during the reduction of the silver ions embedded inside the sol-gel matrix. With the use of a He-Ne laser at a power of only 12 mW, it is possible to measure dopamine in the micromolar concentration range. A single-fiber SERS probe syst...
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Esentürk, Okan; MELINGER, Joseph S.; HEILWEIL, Edwin J. (2010-01-27)
Femtosecond pump-probe methods are useful tools for investigating transient electronic and vibrational states of conducting materials and molecular photochemistry. Ultraviolet and visible excitation pulses (<150 fs, <20 μJ, 400-800 nm) with time-delayed broadband terahertz (~500 GHz to 3 THz) probing pulses (Time-Resolved Terahertz Spectroscopy; TRTS) are used to measure linear spectroscopic transmission changes resulting from exciton and free carrier population in organic semiconducting thin films. Picosec...
Use of gold nanoparticle containing poly (allylamine hydrochloride)/ poly (acrylic acid) multilayer films as sers substrates
Kölemen, Birsu; Ertaş, Gülay; Erel Göktepe, İrem; Department of Chemistry (2015)
Surface-enhanced Raman spectroscopy (SERS) is a surface sensitive vibrational spectroscopy technique that results in the enhancement of Raman scattering by molecules adsorbed on rough metal surfaces. It is a powerful, sensitive and non-destructive technique which is used in chemical, material and life sciences including biosensing, catalysis, spectroelectrochemistry, criminology, single molecule SERS applications and many others. Nanoparticle (NP) embedded multilayer films using Layer by Layer (LbL) techniq...
Citation Formats
B. Cengiz, “Fiber loop ring down spectroscopy for trace chemical detection,” M.S. - Master of Science, Middle East Technical University, 2013.