scholarly journals Cyclic allylic sulfide based photopolymer for holographic recording showing high refractive index modulation

2021 ◽  
Author(s):  
Paola Galli ◽  
Richard A. Evans ◽  
Chiara Bertarelli ◽  
Andrea Bianco
Keyword(s):  
Refractive Index ◽  
High Refractive Index ◽  
Holographic Recording ◽  
Refractive Index Modulation ◽  
Index Modulation

ATOP Dyes. Optimization of a Multifunctional Merocyanine Chromophore for High Refractive Index Modulation in Photorefractive Materials

2001 ◽  
Vol 123 (12) ◽  
pp. 2810-2824 ◽  
Author(s):  
Frank Würthner ◽  
Sheng Yao ◽  
Joachim Schilling ◽  
Rüdiger Wortmann ◽  
Mesfin Redi-Abshiro ◽  
...  
Keyword(s):  
Refractive Index ◽  
High Refractive Index ◽  
Refractive Index Modulation ◽  
Photorefractive Materials ◽  
Index Modulation

scholarly journals Analysis of Long Period Gratings Inscribed by CO2 Laser Irradiation and Estimation of the Refractive Index Modulation

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6409
Author(s):  
Ana M. Rocha ◽  
Ana I. Machado ◽  
Telmo Almeida ◽  
Joana Vieira ◽  
Margarida Facão
Keyword(s):  
Refractive Index ◽  
Laser Irradiation ◽  
Refractive Index Change ◽  
Coupling Model ◽  
High Refractive Index ◽  
Refractive Index Modulation ◽  
Index Change ◽  
Long Period ◽  
Long Period Gratings ◽  
Index Modulation

Long period gratings (LPGs) inscribed in single mode fibers (SMFs) using CO2 laser irradiation were modelled numerically using the coupled mode method. The model considers the specifications of the inscription technique, such as the shape of the refractive index modulation that mimics the circularly symmetric point-to-point laser irradiation profile. A simple expression for predicting the resonant wavelength was obtained assuming a two-mode coupling model. However, to explain the spectra of the experimental LPGs, it was necessary to assume a reasonably high refractive index change and a multimode coupling model. Furthermore, using the developed model and a genetic algorithm to fit experimental resonances to simulated ones, we were able to estimate the maximum refractive index change, obtaining a value of 2.2 × 10−3, confirming the high refractive index change. The proposed model also predicts a second order resonance for this high value of refractive index change that was confirmed experimentally. Hence, with this model, we found some significant differences in the LPGs behavior when compared with conventional ones, namely, the emergence of coupling between different cladding modes and the competition of first and second order resonances which change the LPG transmission spectrum.

scholarly journals A Comparative Cytotoxic Evaluation of Acrylamide and Diacetone Acrylamide to Investigate Their Suitability for Holographic Photopolymer Formulations

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Dervil Cody ◽  
Alan Casey ◽  
Izabela Naydenova ◽  
Emilia Mihaylova
Keyword(s):  
Refractive Index ◽  
Large Scale ◽  
Lethal Dose ◽  
Device Fabrication ◽  
Holographic Recording ◽  
Refractive Index Modulation ◽  
Diacetone Acrylamide ◽  
Wide Range ◽  
Holographic Device ◽  
Index Modulation

The comparative cytotoxic evaluation of two monomers, diacetone acrylamide (DA) and acrylamide (AA) used in holographic photopolymer formulations, is reported. Two normal cell lines were used: BEAS-2B and HaCaT. Cellular viability was assessed using the MTT assay for three different exposure times. A difference of two orders of magnitude is observed in the lethal dose (LD50) concentrations of the two monomers. Diacetone acrylamide exhibits a significantly lower toxicity profile in comparison to acrylamide at all exposure times. This result justifies the replacement of acrylamide with diacetone acrylamide in the photopolymer formulation, with the view to reducing occupational hazard risks for large-scale holographic device fabrication. A comparative study investigating the holographic recording ability of the two photopolymers in transmission mode showed that the DA photopolymer is capable of reaching refractive index modulation values of3.3×10-3, which is 80% of the refractive index modulation achieved by the AA photopolymer. This makes the DA-based photopolymers suitable for a wide range of applications.

scholarly journals Ag nanoparticle-enhanced alkyl radical generation in photopolymerization for holographic recording

Nanophotonics ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1795-1802 ◽  
Author(s):  
Jinxin Guo ◽  
Jialing Jian ◽  
Meng Wang ◽  
Yasuo Tomita ◽  
Lin Cao ◽  
...  
Keyword(s):  
Refractive Index ◽  
Ag Nanoparticles ◽  
Polymer Nanocomposite ◽  
Dark Field ◽  
Holographic Recording ◽  
Refractive Index Modulation ◽  
Modulation Amplitude ◽  
Ag Nanoparticle ◽  
Paramagnetic Resonance ◽  
Index Modulation

AbstractWe report a new Ag nanoparticle-dispersed polymer nanocomposite for volume holographic recording through acrylic photopolymerization. The initial grating buildup dynamics at the inhibition stage are measured at various Ag nanoparticle concentrations. The refractive index modulation amplitude as large as 0.0069 at 633 nm is seen at the optimum Ag nanoparticle concentration of 1 wt.% with respect to the monomer. Electron paramagnetic resonance measurements show that Ag nanoparticles influence both the generation of alkyl radicals and the scavenging of oxygen in free radical photopolymerization. This mechanism intrinsically determines the molecular weight of polymer being formed and, thereby, affects the refractive index modulation amplitude of the formed grating as a function of Ag nanoparticle concentrations. Moreover, we confirm that two-beam holographic exposure leads to a periodic assembly of dispersed Ag nanoparticles using a dark-field microscopy. Our results suggest a simple way to control the photopolymerization and, therefore, to tailor polymers for practical uses.

scholarly journals Effect of Glycerol on an N-Vinylpyrrolidone-Based Photopolymer for Transmission Holography

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1754
Author(s):  
Huishi Pi ◽  
Weiping Li ◽  
Zhiwei Shi ◽  
Haining Chen ◽  
Xiaoyu Jiang
Keyword(s):  
Molecular Structure ◽  
Refractive Index ◽  
Diffraction Efficiency ◽  
Optimal Concentration ◽  
Diffractive Optics ◽  
Holographic Recording ◽  
Control Group ◽  
Refractive Index Modulation ◽  
Spatial Frequencies ◽  
Index Modulation

N-vinylpyrrolidone (NVP) has a large molecular structure, so it is difficult to diffuse during holographic recording, especially at low spatial frequencies. We used glycerol to promote the diffusion of NVP, and successfully improved the holographic performance of the photopolymer at low spatial frequencies. As the concentration of glycerol increases, the holographic performance first increases and then remains stable. The optimal concentration of glycerol is 0.21 mol/L. At this concentration, the maximum diffraction efficiency of the photopolymer is 84%, the refractive index modulation is 1.95 × 10−3, and the photosensitive sensitivity is 7.91 × 10−4 cm2/mJ. Compared with the control group, the maximum diffraction efficiency, maximum refractive index modulation and photosensitivity at low spatial frequencies (800 lp/mm) have increased by 11.19 times, 4.69 times and 1.71 times, respectively. Using the optimized photopolymer for transmission holographic recording and reproduction, we have obtained a clear and bright transmission hologram. The photopolymer modified with glycerol is expected to be applied to the fields of holography, diffractive optics, and so on.

scholarly journals Study of the Effect of Methyldiethanolamine Initiator on the Recording Properties of Acrylamide Based Photopolymer

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 734
Author(s):  
Brian Rogers ◽  
Suzanne Martin ◽  
Izabela Naydenova
Keyword(s):  
Refractive Index ◽  
Diffraction Efficiency ◽  
Prolonged Exposure ◽  
Uv Light ◽  
Holographic Recording ◽  
Refractive Index Modulation ◽  
Optical Elements ◽  
The Stability ◽  
Angular Selectivity ◽  
Index Modulation

The use of Holographic Optical Elements (HOEs) in applications, such as in light shaping and redirection, requires certain characteristics such as a high Diffraction Efficiency, low angular selectivity and stability against UV damage. In order to maximize the performance of the HOEs, photosensitive materials are needed that have been optimised for the characteristics that are of particular importance in that application. At the core of the performance of these devices is the refractive index modulation created during holographic recording. Typically, a higher refractive index modulation will enable greater light Diffraction Efficiency and also operation with thinner devices, which in turn decreases the angular selectivity and the stability of the refractive index modulation introduced during recording, which is key to the longevity of the device. Solar concentrators based on volume HOEs can particularly benefit from thinner devices, because, for a solar concentrator to have a high angular working range, thinner photopolymer layers with a smaller angular selectivity are required. This paper presents an optimisation of an acrylamide-based photopolymer formulation for an improved refractive index modulation and recording speed. This was achieved by studying the effect of the concentration of acrylamide and the influence of different initiators in the photopolymer composition on the diffraction efficiency of holographic gratings. Two initiators of different molecular weights were compared: triethanolamine (TEA) and methyldiethanolamine (MDEA). A fivefold increase in the rate of grating formation was achieved through the modification of the acrylamide concentration alone, and it was also found that holograms recorded with MDEA as the initiator performed the best and recorded up to 25% faster than a TEA-based photopolymer. Finally, tests were carried out on the stability of the protected and unprotected photopolymer layers when subjected to UV light. The properties exhibited by this photopolymer composition make it a promising material for the production of optical elements and suitable for use in applications requiring prolonged exposure to UV light when protected by a thin melinex cover.

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