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- Photopolymers (8)
- Photopolymer (6)
- Holography (5)
- Holographic gratings (4)
- Holographic recording (4)
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- Nanocomposites (3)
- Optical properties (3)
- Diffusion (2)
- Diffusion model (2)
- Holographic sensors (2)
- Humidity indicator (2)
- Polymer (2)
- Porosity (2)
- Surface relief profile (2)
- AFM (1)
- Acrylamide-based photopolymer layer (1)
- Anchoring Energy (1)
- Bistability (1)
- Chiral (1)
- Corona discharge (1)
- Crystal (1)
- DBD plasma (1)
- DSC (1)
- Dielectric permittivity (1)
- Dielectric spectroscopy (1)
- Diffraction efficiency (1)
- Diffraction pattern (1)
- Ferroelectric Liquid Crystals (1)
- Ferroelectric nematics (1)
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Articles 1 - 24 of 24
Full-Text Articles in Physics
Collective Relaxation Processes In Nonchiral Nematics, Neelam Yadav, Yuri Panarin, Wanhe Jiang, Georg H. Mehl, Jagdish Vij
Collective Relaxation Processes In Nonchiral Nematics, Neelam Yadav, Yuri Panarin, Wanhe Jiang, Georg H. Mehl, Jagdish Vij
Articles
Nematic–nematic transitions in a highly polar nematic compound are studied, in thick cells in which the molecules are aligned parallel to the substrates but perpendicular to the applied electric field, using dielectric spectroscopy in the frequency range 1 Hz to 10 MHz over a wide temperature range. The studied compound displays three nematic phases under cooling from the isotropic phase: ubiquitous nematic N; high polarizability NX; and ferroelectric nematic NF. Two collective processes were observed. The dielectric strength and relaxation frequency of one of the processes P2 showed a dependence on the thickness of the cell. The process P1 is …
A Soft Condensed Matter Approach Towards Mathematical Modelling Of Mass Transport And Swelling In Food Grains, Michael Chapwanya, N. Misra
A Soft Condensed Matter Approach Towards Mathematical Modelling Of Mass Transport And Swelling In Food Grains, Michael Chapwanya, N. Misra
Articles
Soft condensed matter (SCM) physics has recently gained importance for a large class of engineering materials. The treatment of food materials from a soft matter perspective, however, is only at the surface and is gaining importance for understanding the complex phenomena and structure of foods. In this work, we present a theoretical treatment of navy beans from a SCM perspective to describe the hydration kinetics. We solve the transport equations within a porous matrix and employ the Flory–Huggin’s equation for polymer–solvent mixture to balance the osmotic pressure. The swelling of the legume seed is modelled as a moving boundary with …
Characterization Of Polylactic Acid Films For Food Packaging As Affected By Dielectric Barrier Discharge Atmospheric Plasma, Shashi Pankaj, Luke O'Neill, N. Misra, Paula Bourke
Characterization Of Polylactic Acid Films For Food Packaging As Affected By Dielectric Barrier Discharge Atmospheric Plasma, Shashi Pankaj, Luke O'Neill, N. Misra, Paula Bourke
Articles
Dielectric barrier discharge (DBD) air plasma is a novel technique for in-package decontamination of food, but it has not been yet applied to the packaging material. Characterization of commercial polylactic acid (PLA) films was done after in-package DBD plasma treatment at different voltage and treatment time to evaluate its suitability as food packaging material. DBD plasma increased the roughness of PLA film mainly at the site in contact with high voltage electrode at both the voltage levels of 70 and 80 kV. DBD plasma treatments did not induce any change in the glass transition temperature, but significant increase in the …
Ultrasound For Improved Crystallisation In Food Processing, N. Misra, Navneet Deora, Brijesh Tiwari, Patrick Cullen
Ultrasound For Improved Crystallisation In Food Processing, N. Misra, Navneet Deora, Brijesh Tiwari, Patrick Cullen
Articles
Within the food industry, controlling crystallisation is a key factor governing food structure, texture and consumer appeal, with some foods requiring the promotion of crystallisation in a controlled manner (e.g. chocolate) and others a check (e.g. in honey). Sonocrystallisation is the application of ultrasound energy to control the nucleation of a crystallisation process. The use of power ultrasound provides a non-invasive approach to producing crystals with desired properties. Sonocrystallisation facilitates process control, primarily by modulating crystal size distribution and morphology. This paper details the governing mechanisms of sonocrystallisation. Proven and potential applications of the process in foods, including chocolates, honey, …
Raman Scattering Analysis Of Silicon Dioxide Single Crystal Treated By Direct Current Plasma Discharge, Dusan M. Poparic, Vladimir Milosavljevic, Andrijana Zekic, N Romcevic, Steven Daniels
Raman Scattering Analysis Of Silicon Dioxide Single Crystal Treated By Direct Current Plasma Discharge, Dusan M. Poparic, Vladimir Milosavljevic, Andrijana Zekic, N Romcevic, Steven Daniels
Articles
Low-k materials such as silicon dioxide (SiO2) play an important role in the semiconductor industry. Plasma has become indispensable for advanced materials processing. In this work a treatment of SiO2single crystal by direct current plasma discharge is studied in detail. Offline metrology is conducted for silicon dioxide wafers by Raman scattering, energy-dispersive x-ray spectroscopy, and ellipsometry. Broad Raman peak at around 2800 cm−1 is observed for the treatedSiO2 wafers. Effects of plasma treatment on position of this peak are reported in the paper. An analysis of this correlation could be a framework for creating virtual etch rate sensors, which might …
Photopolymerizable Nanocomposites For Holographic Recording And Sensor Application, Elsa Leite, Izabela Naydenova, Svetlana Mintova, Louis Leclercq, Vincent Toal
Photopolymerizable Nanocomposites For Holographic Recording And Sensor Application, Elsa Leite, Izabela Naydenova, Svetlana Mintova, Louis Leclercq, Vincent Toal
Articles
Novel nanocomposites consisting of a water soluble acrylamide–based photopolymer and colloidal zeolite nanoparticles of zeolite Beta and zeolite A were prepared. The interactions between the photopolymer components and zeolite nanoparticles in the photopolymerizable nanocomposites were characterized for the first time by 13C NMR and Visible spectroscopy. It was found that the zeolite Beta nanoparticles (up to 5% wt.) behave as a non-inert additive, resulting in an effective increase in layer thickness that causes doubling of the diffraction efficiency of the nanocomposite in comparison to that of the undoped photopolymer. On the other hand, the nanocomposite containing zeolite A nanoparticles showed …
Two-Way Diffusion Model For Short Exposure Holographic Grating Formation In Acrylamide-Based Photopolymer, Tzvetanka Babeva, Izabela Naydenova, Dana Mackey, Suzanne Martin, Vincent Toal
Two-Way Diffusion Model For Short Exposure Holographic Grating Formation In Acrylamide-Based Photopolymer, Tzvetanka Babeva, Izabela Naydenova, Dana Mackey, Suzanne Martin, Vincent Toal
Articles
A theoretical model for formation of a short exposure holographic grating is presented. The model accounts for both monomer and polymer diffusion and distinguishes between short polymer chains capable of diffusing and long polymer chains that are immobile. It is shown that the experimentally observed decrease of diffraction efficiency at higher spatial frequency can be predicted by assuming diffusion of short-chain polymers away from the bright fringes. The time evolution of the refractive index modulation after short exposure is calculated and compared with experimental results. The effects of diffusion coefficients, polymerization rates, intensity and spatial frequency of recording on the …
Optical Properties Of Photopolymer Layers Doped With Aluminophosphate Nanocrystals, Elsa Leite, Tzvetanka Babeva, E Ng, Vincent Toal, Svetlana Mintova, Izabela Naydenova
Optical Properties Of Photopolymer Layers Doped With Aluminophosphate Nanocrystals, Elsa Leite, Tzvetanka Babeva, E Ng, Vincent Toal, Svetlana Mintova, Izabela Naydenova
Articles
The optical properties of photopolymer layers consisting of an acrylamide–based matrix and microporous aluminophosphate nanocrystals of AEI- type are investigated. The compatibility of the photopolymer doped with the nanoparticles is studied. The surface and volume properties of the layers with different levels of doping with microporous nanocrystals are characterized. The effective refractive indices and absorption coefficients of the doped photopolymer layers are determined and used to calculate the refractive index and porosity of pure AEI nanoparticles used as dopants. Volume transmission gratings were recorded in the doped photopolymer layers at different spatial frequencies. By spatial monitoring of the characteristic Raman …
Optimisation Of An Acrylamide-Based Photopolymer System For Holographic Inscription Of Surface Patterns With Sub-Micron Resolution, Kevin Trainer, Kevin Wearen, Dimana Nazarova, Izabela Naydenova, Vincent Toal
Optimisation Of An Acrylamide-Based Photopolymer System For Holographic Inscription Of Surface Patterns With Sub-Micron Resolution, Kevin Trainer, Kevin Wearen, Dimana Nazarova, Izabela Naydenova, Vincent Toal
Articles
We describe the optimisation of the holographic patterning of sub-micrometer surface relief structures in an acrylamide-based photopolymer. A substantial improvement in the photoinduced surface relief resolution was achieved by altering the photopolymer chemical composition and by introducing a single step post recording thermal treatment of the layers. It was observed that, by optimisation of the chemical composition of the photopolymer layers, the maximum achievable spatial frequency increases from 200 l/mm to 550 l/mm. The improvement of the surface relief amplitude by alteration of the chemical composition is limited due to the fact that both decrease of the plasticiser and increase …
A Diffusion Model For Spatially Dependent Photopolymerization, Dana Mackey, Tzvetanka Babeva, Izabela Naydenova, Vincent Toal
A Diffusion Model For Spatially Dependent Photopolymerization, Dana Mackey, Tzvetanka Babeva, Izabela Naydenova, Vincent Toal
Articles
Photopolymers represent an attractive class of optical recording materials due to properties such as high refractive index modulation, dry film processing, long shelf life, etc. Applications include holographically based devices for optical storage disks, optical interconnections, optical memories and filters. This paper will address the dynamics of short-exposure holographic grating formation; a new mathematical model is proposed with the aim of understanding the experimental observations of low diffraction efficiency in high spatial frequency gratings.
Optical Properties Of Photopolymerisable Nanocomposites Containing Zeolite Nanoparticles, Izabela Naydenova, Tzvetanka Babeva, Elsa Leite, Nitesh Pandey, Temenujka Yovcheva, Svetlana Mintova, Vincent Toal
Optical Properties Of Photopolymerisable Nanocomposites Containing Zeolite Nanoparticles, Izabela Naydenova, Tzvetanka Babeva, Elsa Leite, Nitesh Pandey, Temenujka Yovcheva, Svetlana Mintova, Vincent Toal
Conference Papers
Acrylamide-based photopolymerisable nanocomposites containing three different types of nanozeolites – Si-MFI, AlPO and BEA, were studied. The influence of the porous nanoparticles on the average refractive index, optical scattering, holographic recording properties and shrinkage were characterised.
Surface Relief Profile Of Photopolymerisable Systems In A Single Illuminated Spot, Tsvetanka Babeva, Dana Mackey, Izabela Naydenova, Suzanne Martin, Vincent Toal
Surface Relief Profile Of Photopolymerisable Systems In A Single Illuminated Spot, Tsvetanka Babeva, Dana Mackey, Izabela Naydenova, Suzanne Martin, Vincent Toal
Conference Papers
The formation of surface relief profile in photopolymerisable systems when illuminated with a focused beam of light is simulated numerically using a two-way diffusion model that accounts both for monomer and short polymer chains diffusion. The concentration and spatial distribution dynamics of monomer, short and long polymer chains are calculated. It is assumed that the surface profile is a linear combination of monomer and polymer concentration with appropriate coefficients accounting for polymer shrinkage. A good agreement between the calculated and the experimentally measured profiles is observed thus demonstrating the successful application of the two way diffusion in modeling this system.
Optical Properties Of Silica-Mfi Doped Acrylamide-Based Photopolymer, Tzvetanka Babeva, Rosen Todorov, Svetlana Mintova, Temenujka Yovcheva, Izabela Naydenova, Vincent Toal
Optical Properties Of Silica-Mfi Doped Acrylamide-Based Photopolymer, Tzvetanka Babeva, Rosen Todorov, Svetlana Mintova, Temenujka Yovcheva, Izabela Naydenova, Vincent Toal
Articles
The optical properties of acrylamide-based photopolymer doped with pure silica MFI-type zeolites are studied by refractometric and spectrophotometric means. Dynamic Light Scattering and Transmission Electron Microscopy are used for zeolite characterization and laser refractometry and White Light Interferometric profilometry are used for surface characterization of the composites. Refractive indices and absorption coefficients of composites are determined from their transmittance and reflectance spectra. The calculated dispersion curves are further used for deriving the zeolites refractive index and porosity and the latter compared to the values of total pore volume obtained from N2-sorption measurements. The impact of the doping level on the …
Holographic Recording In Acrylamide Photopolymers: Thickness Limitations, Mohammad Mahmud, Izabela Naydenova, Nitesh Pandey, Tzvetanka Babeva, Raghavendra Jallapuram, Suzanne Martin, Vincent Toal
Holographic Recording In Acrylamide Photopolymers: Thickness Limitations, Mohammad Mahmud, Izabela Naydenova, Nitesh Pandey, Tzvetanka Babeva, Raghavendra Jallapuram, Suzanne Martin, Vincent Toal
Articles
Holographic recording in thick photopolymer layers is important for application in holographic data storage, volume holographic filters and correlators. Here, the characteristics of acrylamidebased photopolymer layers having thickness from 250 μm to 1-mm were studied. For each layer thickness samples with three different values of absorbance were studied. By measuring both the first order diffraction efficiency growth of holographically recorded gratings and studying the diffraction patterns obtained, the influence of scattering on the diffraction efficiency of thick volume holographic gratings was analyzed. It was observed that above a particular thickness and absorbance, the first order diffraction efficiency significantly decreased because …
Optical Properties Of Charged Polymer With Nano-Sized Zeolite Inclusions, Temenujka Yovcheva, Izabela Naydenova, Ivanka Vlaeva, Rosen Todorov, Vincent Toal, Simeon Sainov
Optical Properties Of Charged Polymer With Nano-Sized Zeolite Inclusions, Temenujka Yovcheva, Izabela Naydenova, Ivanka Vlaeva, Rosen Todorov, Vincent Toal, Simeon Sainov
Conference Papers
The optical characteristics of photopolymer films doped with nanoparticles are studied. The investigated systems consist of a soft polymer matrix containing porous zeolite nanoparticles with concentrations varied in the range from 0wt.% to 7wt.%. 40μm thick layers are obtained by casting the photopolymer nanocomposite solution on glass substrates. The corona charging influence on the transmission spectra and on the surface and the effective refractive index of the dry layers is investigated.
Recent And Emerging Applications Of Holographic Photopolymers And Nanocomposites, Izabela Naydenova, Pavani Kotakonda, Raghavendra Jallapuram, Tsvetanka Babeva, Denis Bade, Suzanne Martin, Vincent Toal, Svetlana Mintova
Recent And Emerging Applications Of Holographic Photopolymers And Nanocomposites, Izabela Naydenova, Pavani Kotakonda, Raghavendra Jallapuram, Tsvetanka Babeva, Denis Bade, Suzanne Martin, Vincent Toal, Svetlana Mintova
Conference Papers
Sensing applications of holograms may be based on effects such as change in the spacing of the recorded fringes in a holographic diffraction grating in the presence of an analyte so that the direction of the diffracted laser light changes, or, in the case of a white light reflection grating, the wavelength of the diffracted light changes. An example is a reflection grating which swells in the presence of atmospheric moisture to indicate relative humidity by a change is the colour of the diffracted light. These devices make use of the photopolymer’s ability to absorb moisture. In a more versatile …
Fabrication Of Switchable Liquid Crystal Devices Using Surface Relief Gratings In Photopolymer, Pavani Kotakonda, Izabela Naydenova, Robert Howard, Suzanne Martin, Vincent Toal
Fabrication Of Switchable Liquid Crystal Devices Using Surface Relief Gratings In Photopolymer, Pavani Kotakonda, Izabela Naydenova, Robert Howard, Suzanne Martin, Vincent Toal
Articles
Holographically recorded surface relief gratings in dry, self-developing acrylamide based photopolymer were used to fabricate two types of switchable liquid crystal (LC) device. One is an electrically switchable LC diffraction grating and the other is an electrically switchable polarization rotator. The electrically switchable diffraction grating was characterized by measuring the dependence of the intensity in the first diffracted order on the applied electric field. The polarization rotator was characterized by studying the influence of the applied electric field on the twist angle and the variation of intensity in the zero and the first orders of diffraction.
Nanocomposites For Novel Holographic Applications, Izabela Naydenova, Svetlana Mintova, Suzanne Martin, Vincent Toal
Nanocomposites For Novel Holographic Applications, Izabela Naydenova, Svetlana Mintova, Suzanne Martin, Vincent Toal
Articles
Nanozeolites incorporated into photopolymerizable holographic recording materials can be used for holographic sensing, data storage, and optical systems design.
Hologram-Based Humidity Indicator For Domestic And Packaging Applications, Izabela Naydenova, Raghavendra Jallapuram, Vincent Toal, Suzanne Martin
Hologram-Based Humidity Indicator For Domestic And Packaging Applications, Izabela Naydenova, Raghavendra Jallapuram, Vincent Toal, Suzanne Martin
Conference Papers
A passive indicator for Relative Humidity based on a photopolymer recorded hologram has been developed. The indicator works on the principle that the wavelength reconstructed by a reflection hologram is dependent on the spacing between the fringe planes of the hologram. As the Relative Humidity changes, the hologram swells or shrinks and the apparent colour of the reconstructed image changes. The response time, operational range and reversibility of the indicator have been studied in a controlled humidity environment. Response times from less than a minute to tens of minutes depending on the holograms physical properties have been measured. Indicators with …
Holographic Recording In Nanoparticle-Doped Photopolymer, Izabela Naydenova, Hosam Sherif, Svetlana Mintova, Suzanne Martin, Vincent Toal
Holographic Recording In Nanoparticle-Doped Photopolymer, Izabela Naydenova, Hosam Sherif, Svetlana Mintova, Suzanne Martin, Vincent Toal
Conference Papers
A nanoparticle-doped acrylic photopolymer is characterised as a material for holographic recording. The influence of nanoparticles on the photopolymer dynamic range, dynamics of recording, temporal stability and mechanical stability in terms of shrinkage has been studied. The dynamics of recording and the temporal stability are investigated by real time monitoring of the build up of diffraction gratings of spatial frequencies of 200 to 2000 l/mm. The shrinkage has been characterised by recording slanted transmission gratings and observation of the change in the Bragg angle.
Characterisation Of An Acrylamide-Based Photopolymer For Data Storage Utilizing Holographic Angular Multiplexing, Hosam Sherif, Izabela Naydenova, Suzanne Martin, Colm Mcginn, Vincent Toal
Characterisation Of An Acrylamide-Based Photopolymer For Data Storage Utilizing Holographic Angular Multiplexing, Hosam Sherif, Izabela Naydenova, Suzanne Martin, Colm Mcginn, Vincent Toal
Articles
An acrylamide-based photopolymer formulated in the Centre for Industrial and Engineering Optics has been investigated with a view to further optimisation for holographic optical storage. Series of 18 to 30 gratings were angularly multiplexed in a volume of photopolymer layer at a spatial frequency of 1500 lines/mm. Since the photopolymer is a saturable material, an exposure scheduling method was used to exploit the entire dynamic range of the material and allow equal strength holographic gratings to be recorded. This investigation yielded the photopolymer M/# for moderately thin layers. Photopolymer temporal stability was also studied by measuring variations of material shrinkage, …
Investigation Of The Diffusion Processes In Self-Processing Acrylamide-Based Photopolymer System, Izabela Naydenova, Raghavendra Jallapuram, Robert Howard, Suzanne Martin, Vincent Toal
Investigation Of The Diffusion Processes In Self-Processing Acrylamide-Based Photopolymer System, Izabela Naydenova, Raghavendra Jallapuram, Robert Howard, Suzanne Martin, Vincent Toal
Articles
Results from the investigation of the diffusion processes in a dry acrylamide-based photopolymer system are presented. The investigation is carried out in the context of experimental work on optimization of the high spatial frequency response of the photopolymer. Tracing the transmission holographic grating dynamics at short times of exposure is utilized to measure diffusion coefficients. The results reveal that two different diffusion processes contribute with opposite sign to the refractive index modulation responsible for the diffraction grating build up. Monomer diffusion from dark to bright fringe areas increases the refractive index modulation. It is characterized with diffusion constant D0=1.6E-7 cm2/s. …
Investigation Of The Photoinduced Surface Relief Modulation In Acrylamide-Based Photopolymer, Izabela Naydenova, Emilia Mihaylova, Suzanne Martin, Vincent Toal
Investigation Of The Photoinduced Surface Relief Modulation In Acrylamide-Based Photopolymer, Izabela Naydenova, Emilia Mihaylova, Suzanne Martin, Vincent Toal
Conference Papers
A surface relief diffraction grating is inscribed in acrylamide photopolymer by holographic recording with spatial frequency below 300 l/mm. The periodic surface modulation appears in addition to a volume phase holographic grating. Due to the nature of the presented photopolymerisable material the gratings are induced by light only and no post-processing is required. An investigation of the dependance of the amplitude of the photoinduced relief modulation on spatial frequency of recording and on sample thickness has been carried out utilising white light interferometry. A model of the mechanism of surface relief formation is proposed on the basis of the measured …
Hysteresis And Anchoring Energy In Ferroelectric Liquid Crystals, Yuri Panarin
Hysteresis And Anchoring Energy In Ferroelectric Liquid Crystals, Yuri Panarin
Articles
The frequency dispersion of the coercive force of Ferroelectric Liquid Crystals (FLC) cells has been detected and examined in the range of infralow (lower than 0.1 Hz) frequencies. To clarify the low-frequency dispersion, the model has been suggested, based on the arrangement of free charges and well describing the experimental curves. The method for determination of the energy of FLC anchoring at the surface, developed on the basis of the static hysteresis loop, has been proposed. The dependence of bistability and the anchoring energy upon the orientant layer thickness has experimentally been investigated.