Rajesh, M; Dr.Nampoori,V P N(Cochin University of Science & Technology, July , 2006)
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Abstract:
The thesis presented the fabrication and characterisation of
polymer optical fibers in their applications as optical amplifier and smart sensors.Optical polymers such as PMMA are found to be a very good host material due
to their ability to incorporate very high concentration of optical gain media like
fluorescent dyes and rare earth compounds. High power and high gain optical
amplification in organic dye-doped polymer optical fibers is possible due to
extremely large emission cross sections of oyes. Dye doped (Rhodamine 6G)
optical fibers were fabricated by using indigenously developed polymer optical
fiber drawing tower. Loss characterization of drawn dye doped fibers was carried
out using side illumination technique. The advantage of the above technique is
that it is a nondestructive method and can also be used for studying the
uniformity in fiber diameter and doping. Sensitivity of the undoped polymer
fibers to temperature and microbending were also studied in its application in
smart sensors.Optical amplification studies using the dye doped polymer optical fibers were
carried out and found that an amplification of l8dB could be achieved using a
very short fiber of length lOcm. Studies were carried out in fibers with different
dye concentrations and diameter and it was observed that gain stability was
achieved at relatively high dye concentrations irrespective of the fiber diameter.Due to their large diameter, large numerical aperture, flexibility and geometrical
versatility of polymer optical fibers it has a wide range of applications in the field
of optical sensing. Just as in the case of conventional silica based fiber optic
sensors, sensing techniques like evanescent wave, grating and other intensity
modulation schemes can also be efficiently utilized in the case of POF based
sensors. Since polymer optical fibers have very low Young's modulus when
compared to glass fibers, it can be utilized for sensing mechanical stress and
strain efficiently in comparison with its counterpart. Fiber optic sensors have
proved themselves as efficient and reliable devices to sense various parameters
like aging, crack formation, weathering in civil structures. A similar type of study
was carried out to find the setting characteristics of cement paste used for
constructing civil structures. It was found that the measurements made by using
fiber optic sensors are far more superior than that carried out by conventional
methods. More over,POF based sensors were found to have more sensitivity as
well.
Description:
International School of Photonics,
Cochin University of Science & Technology
Samuel Varghese, K; Dr.Nampoori,V P N; Dr.Girijavallabhan,C P(Cochin University of Science and Technology, December , 2008)
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Abstract:
This Thesis deals with the fabrication and characterization of novel all-fiber components for access networks. All fiber components offer distinctive advantages due to low forward and backward losses, epoxy free optical path and high power handling. A novel fabrication method for monolithic 1x4 couplers, which are vital components in distributed passive optical networks, is realized. The fabrication method differs from conventional structures with a symmetric coupling profile and hence offers ultra wideband performance and easy process control. New structure for 1x4 couplers, by fusing five fibers is proposed to achieve high uniformity, which gives equivalent uniformity performance to 1x4 planar lightwave splitters, isolation in fused fiber WDM is improved with integration of long period gratings. Packaging techniques of fused couplers are analyzed for long term stability.
Description:
International School of Photonics, Cochin University of Science and Technology
Tintu, R; Dr. Sheenu, Thomas(Cochin University of Science and Technology, June , 2011)
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Abstract:
In this context,in search of new materials based on chalcogenide glasses,we have developed a novel technique for fabrication of chalcogenide nano composites which are presented in this theis.The techniques includes the dissolution of bulk chalcogenide glasses in amine solvent.This solution casting method allows to retain the attractive optical properties of chalcogenide glasses enabling new fabrication routes for realization of large area thick-thin films with less cost. Chalcogenide glass fiber geometry opens new possibilities for a large number of applications in optics,like remote temperature measurements ,CO2 laser power delivery, and optical sensing and single mode propagation of IR light.We have fabricated new optical polymer fibers doped with chalcogenide glasses which can be used for many optical applications.The present thesis also describes the structural,thermal and optical characterization of certain chalocogenide based materials prepared for different methods and its applications.
Description:
International School of Photonics, Cochin University of Science and Technology
Beena,Mary John; Sudha Kartha, C(Department of Physics, January , 2008)
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Abstract:
Holographic technology is at the dawn of quick evolution in various new
areas including holographic data storage, holographic optical elements, artificial
intelligence, optical interconnects, optical correlators, commerce, medical practice,
holographic weapon sight, night vision goggles and games etc. One of the major
obstacles for the success of holographic technology to a large extent is the lack of
suitable recording medium.
Compared with other holographic materials such as dichromated gelatin
and silver halide emulsions, photopolymers have the great advantage of recording
and reading holograms in real time and the spectral sensitivity could be easily
shifted to the type of recording laser used by simply changing the sensitizing dye.
Also these materials possess characteristics such as good light sensitivity, real
time image development, large dynamic range, good optical properties, format
flexibility, and low cost. This thesis describes the attempts made to fabricate
highly economic photopolymer films for various holographic applications.
In the present work, Poly (vinyl alcohol) (PVA) and poly (vinyl chloride)
(PVC) are selected as the host polymer matrices and methylene blue (MB) is used
as the photosensitizing dye. The films were fabricated using gravity settling
method. No chemical treatment or pre/post exposures were applied to the films.
As the outcome of the work, photopolymer films with more than 70% efficiency, a
permanent recording material which required no fixing process, a reusable
recording material etc. were fabricated.
Sheeba, M; Dr. Radhakrishnan, P(Cochin University of Science and Technology, May 22, 2008)
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Abstract:
Although the main application of optical fibers are in the field of
telecommunication, optical fiber based sensors of various designs are
becoming valuable devices for wide industrial applications. The
advantages of optical fiber-based sensors include high sensitivity,
insensitivity to electromagnetic radiation; spark free, light weight and
minimal intrusiveness due to their relatively small size and deployment in
harsh and hostile environments. It has been proved that POI-7 based
sensors can be employed to detect a great variety of parameters including
temperature, humidity, pressure, refractive index etc.
The proposed thesis presented in six chapters deals with the work carried
on dye doped and undoped POF for photonic device applications such as
amplifier, laser and sensor
Description:
International School of Photonics
Cochin University of Science and Technology
Varkey,K P; Dr.Vijayakumar, K P(COCHIN UNIVERSITY OF SCIENCE AND TECHNOLOGY, August , 1999)
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Abstract:
The study on the fabrication and characterization of spray pyrolysed cadmium sulphide homojunction solar cells. As an alternative to the conventional energy source, the PV technology has to be improved. Study about the factors affecting the performance of the existing solar cells and this will result in the enhancement of efficiency of the cells. At the same time it is equally important to have R&D works on developing new photovoltaic devices and processes which are less expensive for large scale production. CdS is an important binary compound semiconductor, which is very useful in the field of photovoltaics. It is very easy to prepare large area CdS thin films. In order to fabricate thin film homojunction cadmium sulphide cells, prepared and characterized SnO2 thin film as the lower electrode, p-CdS as the active layer and n-CdS as window layer. Cadmium material used for the fabrication of homojunction solar cells is highly toxic. The major damage due to continued exposure to low levels of cadmium are on the kidneys, lungs and bones. The real advantage of spray pyrolysis process is that there is no emission of any toxic gases during the deposition. Very low concentration of the chemicals is needed in this process. The risk involved from this material is very low, though they are toxic. On large scale usage it may become necessary that the cells after their life, should be bought back by the companies to retrieve chemicals like cadmium. This will reduce environmental problem and also the material wastage
Sebastian, P J; Dr.Sathianandan, K(Cochin University Of Science And Technology, November 25, 1981)
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Abstract:
Eventhough a large number of schemes have been proposed and develoned for N9 laser ouined dye lasers the
relatively low efficiency compelled the scientists to
device new methods to improve the system efficiencs.
Energy transfer mechanism has been shown to he a convenien
tool for the enhancement of efficiency of dye lasers. Th
p resent work covers a detailed study of the performance
characteristics of a N2 laser pumped dye laser in the con—
ventional mode and also, when pumped by the energy transfer
mechanism. For .th.e present investigations a dye laser
pumped by a'N2 laser (A4200 kw peak power) was fabricated.
The grating at grazing incidence was used as the beam expanding
device; A t its best performance the system was
giving an output peak power of l5 kW for a 5 X lC"3H/l Rh—€
solution in methanol. T he conversion efficiency was 7.5;
The output beam was having 3 divergence of 2 mrad and bandwidth
o.9 A. Suitable modifications were suggested for
obtaining better conversion efficiency and bandwidth.
Description:
Department of Physics,
Cochin University Of Science And Technology
Jayaraj, M K; Dr.Girijavallabhan,C P(Cochin University of Science and Technology, June 20, 1988)
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Abstract:
This thesis contains the author's work in preparing efficient EL phosphors, the details of fabrication of low voltage operated thin film EL (TFEL) devices and DC TFEL devices. Some of the important work presented here are related to the white light emitting ZnS:Cu,Pr,Cl phosphor which can be colour tuned by changing the excitation frequency, observation of energy transfer from Cu/Ag ions to rare earth ions in ZnS:(Cu/Ag), RE,Cl phosphors, development of TFEL device which can be operated below 50V, optimization of the device parameters for long life, high brightness in terms of the active and insulating layer thicknesses, observation of dependence of threshold voltage for the onset of emission on frequency of excitation when a novel dielectric Eu2O3 film was used as insulator and the devices with multicolor emission using ZnS doped with rare earth as active layer. Characterization based on other devices based on ZnS:Sm, ZnS:Pr, ZnS:Dy and their emission characteristics are also illustrated
Description:
Department of Physics, Cochin University of Science and Technology
Sareena, John; Dr.Girish Kumar, K(Cochin University of Science and Technology, December , 2007)
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Abstract:
Potentiometric chemical sensors,an important class of electro-chemical sensors are widely used in pharmaceutical analysis because of its inherent advantages.The present study was aimed at fabrication of potentiometric sensors for the drugs mebendazole,pefloxacin,ambroxol,sildenafil citrate,dextro-methorphan and tetracycline.A total of 18 sensors have been developed for the determination of theses drugs.The major step in the fabrication of the sensor was the preparation of the ion association.Two types of sensors viz:PVC membrane sensor and carbon paste electode (CPE) were fabricated.The response characteristics of the different sensors fabricated were studied.Various response parameters studied include response time,selectivity and the effect of pH.The developed sensors were also employed for the determination of the drugs in pharmaceutical formulations and also for the recovery of the drug from urine samples.The selectivity studies reveal that the developed sensors are highly selective to the drug even in prescence of foreign ions.
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology
Sindhu, Issac; Dr.Girish Kumar, K(Cochin University of Science & Technology, February , 2011)
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Abstract:
Voltammetric sensors are an important class of electrochemical sensors in which the analytical information is obtained from the measurement of current obtained as a result of electrochemical oxidation/reduction.This current is proportional to the concentration of the analyte.Chemically modified electrodes(CMEs) have great significance as important analytical tools for the electrochemical determination of pharmaceuticals.The modification of electrode results in efficient determination of electro-active biomolecules at very lower potential without its major interferences.The operation mechanism of CMEs depends on the properties of the modifier materials that are used to promote selectivity towards the target analytes.Modified electrodes can be prepared by deposition of various compounds such as organic compounds ,conducting polymers,metal oxides,etc. on the various electrode surfaces.The thesis presents the development ,electrochemical characterization and analytical application studies of eight voltammetric sensors developed for six drugs viz.,Ambroxol,Sulfamethoxazole,PAM Chloride, Lamivudine,Metronidazole and Nimesulide.The modification techniques adopted as part of the present work include Multiwalled Carbon Nanotube(MWCNT) based modification.Electropolymerisation and Gold Nanoparticle (AuNP) based modifications.
Description:
Dept.of Applied Chemistry,Cochin University of Science & Technology
Remalakshmy,Poduval; Girish Kumar,K(Department of applied chemistry, 2006)
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Abstract:
In this study Fabrication of Potentiometric sensors for the determination of certain metal ions, presents the synthesis and characterization of seven ionophores, their use in the fabrication of potentiometric sensors and the results and discussion of fourteen sensors developed for the determination of five transition metal ions. As part of the present investigations a total of fourteen potentiometric sensors have been developed and fabricated. A three fold approach has been taken in developing he sensors, PVC plasticized membrane sensor, carbon paste electrode and chemically modified carbon paste electrode. All the sensors are highly useful in the determination of metal ions such as manganese, nickel, copper, mercury and lead. A through analytical study has been carried out with respect to each other developed. Based on these studies, optimum conditions have been developed for the quantitative determinations of the selected metal ions using the sensors. Systematic application studies have also been carried out for all the developed sensors and the results revealed that the presently developed sensors are far superior than most of the sensors reported.
Beena, S; Dr.Girish Kumar, K(Cochin University of Science and Technology, May , 2010)
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Abstract:
In many fields such as earth science biology, environment and electronics, the knowledge about elemental distributions and chemical speciation is important. The determination of metal levels especially the toxic ones both in the environment and in biological materials are increasingly demanded by the society.Ion selective sensors have become one of the most effective ad powerful means for analytical scientists for the trace level monitoring of metal ions. The wide range of applications ,low material requirements and simplicity of analytical procedure have not only brought ion-selective electrodes in to the lime light of analytical chemistry,but have promoted their use as tools for physiologists,medical researchers,biologists,geologists,environmental protection specialists etc.Potentiometric ion-selective sensors have been developed for the determination of lanthanide ions such as La3+,Nd3+,Pr3+,Sm3+, and Gd3+.The sensors fabricated include both PVC membrane sensor and chemically modified carbon paste sensor. A set of 10 sensors have been developed. The response parameters of all the sensors have been studied and the sensors were applied as an indicator electrode in the potentiometric titration and for the determination of metal ions in real samples.
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology