Copper Doped Methylene Blue Sensitized Poly(vinyl alcohol)–Acrylamide Films for Stable Diffraction Efficiency

Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)–acrylamide films were fabricated to improve the storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride concentration was optimized as 3:18 10 3 mol/l for a dye concentration of 6:2 10 4 mol/l. The gratings recorded on the optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.

Copper Doped Methylene Blue Sensitized Poly(vinyl alcohol)–Acrylamide Films for Stable Diffraction Efficiency

Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)–acrylamide films were fabricated to improve the storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride concentration was optimized as 3:18 10 3 mol/l for a dye concentration of 6:2 10 4 mol/l. The gratings recorded on the optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.

Enhancement of Diffraction Efficiency and Storage Life of Poly (Vinyl Chloride) Based Optical Recording Medium with the Incorporation of an Electron Donor

The differaction efficiency,sensitivity and storage life of Methylene Blue sencitized poly (vinyl chloride) film was improved by the addition of an electron donor in the matrix. The addition of pyridine enhanced the diffraction efficiency by two times and storage life of the gratings was increased to 2-3 days.

Copper Doped Methylene Blue Sensitized Poly(vinyl alcohol)–Acrylamide Filmsfor Stable Diffraction Efficiency

Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)–acrylamide films were fabricated to improve the storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride concentration was optimized as 3:18 10 3 mol/l for a dye concentration of 6:2 10 4 mol/l. The gratings recorded on the optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.

Enhancement of Diffraction Efficiency and Storage Life of Poly (Vinyl Chloride) Based Optical Recording Medium with the Incorporation of an Electron Donor

The differaction efficiency,sensitivity and storage life of Methylene blue sensitized poly(vinyl chloride) film was improved by the addition of an electron donor in the matrix. The addition of pyridine enhanced the diffraction efficiency by two times and storage life of the gratings was increased to 2-3 days.

Effect of Concentration of DYE on the Storage Life of Plane Wave Gratings on Photopolymer Film

Holographic grating with good storage life in poly(vinyl alcohol) based photopolymer film, prepared by gravity settling method, with reduced concentration of the dye was found to give good diffraction efficiency without crosslinking. The material was found to show good diffraction efficiency and sensitivity (75% diffraction efficiency at exposure energy of 80 mJ/cm2). The shelf life of the photopolymer solution could be improved by storage at a temperature 4 C in refrigerator

Effect of Chromium Doping on the Diffraction Efficiency of Methylene Blue Sensitized PVA/Acrylamide Films

The effect of chromium doping on methylene blue sensitized Poly (vinyl alcohol)/Acrylamide was carried out by varying the ratios of Ammonium dichromate and methylene blue. In the case of films without ammonium dichromate, the diffraction efficiency was found to decrease on storage. On chromium doping the storage life was improved. Interestingly, a self-enhancement in efficiency was observed for a particular ratio of methylene blue and ammonium dichromate.

A multiple-building diffraction attenuation function expressed in terms of UTD coefficients for microcellular communications

This work presents an explicit formulation for multiple- edge diffraction for mobile radiowave propagation in terms of uniform theory of diffraction (UTD) coefficients when a spherical incident wave is considered. This solution can be used in an UTD context and sharply reduces the computing time over existing formulation. Results can be applied in the planning of microcellular systems

A new metal ion doped panchromatic photopolymer for holographic applications

This thesis has discussed the development of a new metal ion doped panchromatic photopolymer for various holographic applications. High-quality panchromatic holographic recording material with high diffraction efficiency, high photosensitivity and high spatial resolution is one of the key factors for the successful recording of true colour holograms. The capability of the developed material for multicolour holography can be investigated.In the present work, multiplexing studies were carried out using He-Ne laser (632.8 nm). Multiplexing can be done using low wavelength lasers like Ar+ ion (488 nm) and frequency doubled Nd: YAG (532 nm) lasers, so as to increase the storage capacity. The photopolymer film studied had a thickness of only 130 Cm. Films with high thickness (~500 Cm) is highly essential for competitive holographic memories . Hence films with high thickness can be fabricated and efforts can be made to record more holograms or gratings in the material.In the present study, attempts were made to record data page in silver doped MBPVA/AA photopolymer film. Image of a checkerboard pattern was recorded in the film, which could be reconstructed with good image fidelity. Efforts can be made to determine the bit error rate (BER) which provides a quantitative measure of the image quality of the reconstructed image . Multiple holographic data pages can also be recorded in the material making use of different multiplexing techniques.Holographic optical elements (HOEs) are widely used in optical sensors, optical information processing, fibre optics, optical scanners and solar concentrators . The suitability of the developed film for recording holographic optical elements like lenses, beam splitters and filters can be studied.The suitability of a reflection hologram recorded in acrylamide based photopolymer for visual indication of environmental humidity is reported . Studies can be done to optimize the film composition for recording of reflection holograms.An improvement in the spatial resolution of PVA/acrylamide based photopolymer by using a low molecular-weight poly (vinyl alcohol) binder was recently reported . Effect of the molecular weight of the binder matrix on the holographic properties of the developed photopolymer system can be investigated.Incorporation of nanoparticles into photopolymer system is reported to enhance the resolution and improve the dimensional stability of the system . Hence efforts can be made to incorporate silver nanoparticles into the photopolymer and its influence on the holographic properties can be studied.This thesis was a small venture towards the realization of a big goal, a competent holographic recording material with excellent properties for practical holographic applications. As a result of the present research, we could successfully develop an efficient panchromatic photopolymer system and could demonstrate its suitability for recording transmission holograms and holographic data page. The developed photopolymer system is expected to have significant applications in the fields of true-color display holography, wavelength multiplexing holographic storage, and holographic optical elements. Highly concentrated and determined effort has yet to be put forth for this expectation to become a reality.

Long period gratings in multimode optical fibers: application in chemical sensing

We propose and demonstrate a new technique for evanescent wave chemical sensing by writing long period gratings in a bare multimode plastic clad silica fiber. The sensing length of the present sensor is only 10 mm, but is as sensitive as a conventional unclad evanescent wave sensor having about 100 mm sensing length. The minimum measurable concentration of the sensor reported here is 10 nmol/l and the operating range is more than 4 orders of magnitude. Moreover, the detection is carried out in two independent detection configurations viz., bright field detection scheme that detects the core-mode power and dark field detection scheme that detects the cladding mode power. The use of such a double detection scheme definitely enhances the reliability and accuracy of the results. Furthermore, the cladding of the present fiber need not be removed as done in conventional evanescent wave fiber sensors.

Studies on Spatial and Temporal solitons with varying dispersion,diffraction and nonlinearity

Department of Physics, Cochin University of Science and Technology

Recording multiple holographic gratings in silver-doped photopolymer using peristrophic multiplexing

Plane-wave transmission gratings were stored in the same location of silver- doped photopolymer ¯lm using peristrophic multiplexing techniques. Constant and vari- able exposure scheduling methods were adopted for storing gratings in the ¯lm using He{Ne laser (632.8 nm). The role of recording geometry on the dynamic range of the ma- terial was studied by comparing the results obtained from both techniques. Peristrophic multiplexing with rotation of the ¯lm in a plane normal to the bisector of the incident beams resulted in better homogenization of di®raction e±ciencies and larger M/# value.

Nonlinear and magneto-optical transmission studies on magnetic nanofluids of non-interacting metallic nickel nanoparticles

Oxide free stable metallic nanofluids have the potential for various applications such as in thermal management and inkjet printing apart from being a candidate system for fundamental studies. A stable suspension of nickel nanoparticles of ∼5 nm size has been realized by a modified two-step synthesis route. Structural characterization by x-ray diffraction and transmission electron microscopy shows that the nanoparticles are metallic and are phase pure. The nanoparticles exhibited superparamagnetic properties. The magneto-optical transmission properties of the nickel nanofluid (Ni-F) were investigated by linear optical dichroism measurements. The magnetic field dependent light transmission studies exhibited a polarization dependent optical absorption, known as optical dichroism, indicating that the nanoparticles suspended in the fluid are non-interacting and superparamagnetic in nature. The nonlinear optical limiting properties of Ni-F under high input optical fluence were then analyzed by an open aperture z-scan technique. The Ni-F exhibits a saturable absorption at moderate laser intensities while effective two-photon absorption is evident at higher intensities. The Ni-F appears to be a unique material for various optical devices such as field modulated gratings and optical switches which can be controlled by an external magnetic field

Investigation on the panchromaticity of silver-doped poly(vinyl alcohol)/acrylamide photopolymer

An investigation on the panchromaticity of a silver-doped poly(vinyl alcohol)/acrylamide photopolymer system is presented in this paper. Frequency-doubled Nd:YAG (532 nm) and Arþ (488 nm) lasers were used for the characterization of the films. Previous studies using an He–Ne laser (632:8 nm) showed that plane-wave transmission grating with a high diffraction efficiency of 75% could be stored in the optimized film. From the present study, it was noted that transmission gratings with 70% diffraction efficiency could be recorded using Arþ and Nd:YAG lasers, thereby elucidating the possibility of using the developed photopolymer system as a competent panchromatic recording medium

Silver-doped photopolymer media for holographic recording

Incorporation of silver ions into a dye-sensitized poly(vinyl alcohol)/acrylamide photopolymer is observed to give better performance compared to other metal-ion-doped photopolymer holographic recording media. Plane-wave transmission gratings were recorded in the photopolymer films using a He–Ne laser, and various holographic parameters were optimized so as to explore maximum potential of the material for various holographic applications. Silver-doped films showed good energy sensitivity, and gratings recorded in optimized film exhibited a diffraction efficiency of more than 75%. The potential of the material for holographic data storage applications is also studied using peristrophic multiplexing