Holographic property of photopolymers with different amine photoinitiators

Holographic parameters and photobleaching kinetics of the photopolymers with five different amine photoinitiators are studied. The maximum values of diffraction efficiency, photobleaching coefficient and quantum yield follow the sequence： Triethanolamine （TEA）〉 Diethanolamine （DEA）〉 Ethanolamine （EA）〉 Triethylamine （TETN）〉 Diethylamine （DETN）. The holographic capabilities of photopolymer performances are determined by the number of functional groups in the amine molecular structure. There is an optimum proportion of the photoinitiator, the photosensitizer and the monomer in the test of holographic parameters with different amine concentrations. The maximum diffraction efficiency is 59.26／%, sensitivity is 1.72／times 10^{ - 3}~cm^{2}/mJ, and the maximum refractive modulation index is 4.64／times 10^{ - 4}.

A new photopolymerizable holographic recording material based on acrylamide and N-hydroxymethyl acrylamide

A new polyvinylalcohol-based photopolymeric holographic recording material has been developed. The recording is obtained by the copolymerization of acrylamide and N-hydroxymethyl acrylamide. Diffraction efficiencies near 50% are obtained with energetic exposure of 80mJ/cm^2. N-hydroxymethyl acrylamide can improve the optical quality of the film. With the increase of the concentration of N-hydroxymethyl acrylamide, the flatness of the film increases, scattering reduces and the straight image is clearer with a small distortion. The postexposure effect on the grating is also studied. The diffraction efficiency of grating increases further during postexposure, gradient of monomer exists after exposure.

Dark diffusional enhancement of holographic multiplexed gratings in phenanthrenequinone doped poly(methyl methacrylate) photopolymer

In this paper, we experimentally investigate the dark diffusional enhancement of the optimized multiplexed grating in the phenanthrenequinone doped poly （methyl methacrylate） （PQ-PMMA） photopolymer. The possibility of improving the holographic characteristics of the material through the dark enhancement is demonstrated. The optimal preillumination exposure and the optimal time interval between exposures are extracted to obtain the optimized diffraction efficiency, and their values are 3.4×103 mJ/cm2 and 2 min, respectively. The dark enhancement of the multiplexed grating is presented as an effective method to improve the response region and the dynamic range and to prevent saturation of the material. The dependence of the phenanthrenequinone concentration on the increment of the refractive index modulation is quantitatively studied, which provides a significant basis for improving the homogeneity in the multiplexed gratings using a quantitative strategy. Finally, a simple experimental procedure using the dark enhancement is introduced to improve the homogeneity of the diffraction efficiency and to avoid the complex schedule exposure.

Holographic storage of three-dimensional image and data using photopolymer and polymer dispersed liquid crystal films

We present holographic storage of three-dimensional（3D） images and data in a photopolymer film without any applied electric field.Its absorption and diffraction efficiency are measured,and reflective analog hologram of real object and image of digital information are recorded in the films.The photopolymer is compared with polymer dispersed liquid crystals as holographic materials.Besides holographic diffraction efficiency of the former is little lower than that of the latter,this work demonstrates that the photopolymer is more suitable for analog hologram and big data permanent storage because of its high definition and no need of high voltage electric field.Therefore,our study proposes a potential holographic storage material to apply in large size static 3D holographic displays,including analog hologram displays,digital hologram prints,and holographic disks.

Compact 2×2 parabolic multimode interference thermo–optic switches based on fluorinated photopolymer

In this work, a dual-side parabolic structural(DSPS) multimode interference(MMI) thermo–optic(TO) waveguide switch is designed and fabricated by using novel low-loss fluorinated photopolymer materials. Comparing with the traditional dual-side linear structural(DSLS) MMI device, the effective length of the MMI coupling region proposed can be effectively reduced by 40%. The thermal stability of the waveguide material is analyzed, and the optical characteristics of the switching chip are simulated. The actual performances of the entire MMI switch are measured with an insertion loss of7 dB, switching power of 15 m W and an extinction ratio of 28 dB. In contrast to the traditional MMI optical switch, the new type of parabolic structural MMI TO waveguide switch exhibits lower power consumption and larger extinction ratio. The compact fluorinated polymer MMI TO switches are suitable well for realizing miniaturization, high-properties, and lower cost of photonic integrated circuits.

STUDY OF DYE-SENSITIZED SYSTEMS FOR PHOTOIMAGING

o-Chloro-hexaarylbiimidazole (o-CI-HABI) can be sensitized efficiently by cyanine dyes, the cyclopentanone and cyclohexanone dyes, when exposed to xenon lamp (use filter cut lambda less than or equal to 400 nm). The photoreaction between the photoinitiator and the dyes was completed through an electron transfer process. Excellent results have been obtained in photoimaging studies, e.g. the resolution of the image can reach 7 mum. The influence of the content of the dyes and the heat after the exposure on the resolution of the image was investigated.

CURING PROCESS OF PHOTOPOLYMER RESIN BOND DIAMOND TOOLS

Analytical simulation and corresponding proof-test are adopted to study the principle of the curing process of photopolymer resin diamond tools. The influence of the diamond as abrasives in photopolymer resin owing to the absorptivity of the diamond for the UV light on the photopolymer resin curing process is discussed. Based on the above, a kind of diamond tool—dicing blade is selected to analyze the curing process of photopolymer bond diamond tools. An analytical model of curing process is developed and a correlation curve between the depth of polymerization of the photopolymer resin diamond tools and the exposure time to represent the curing process of photopolymer bond dicing blade. A test is done to proof-test the validity of the analytical model and the correlation curve. The simulated data fit the experimental results, which demonstrates the analytical models and numerical algorithm are of high reliability. The analytical simulation method could possibly be used to optimize the curing cycle and improve the quality of the photopolymers resin bond diamond tools.

Dynamic analysis of holographic gratings in a multi-wavelength visible light sensitive photopolymer

A dynamic theoretical model of photochemistry and hologram formation in holographic photopolymer is established, and the dynamic development process of holographic gratings in the photopolymer is discussed with the model. A novel multi-wavelength visible light sensitive photopolymer for holographic storage is prepared. The influence of exposure wavelength on holographic storage characteristics is analysed. By fitting the experimental data of transmittance and diffraction efficiency to a function of time with different exposure intensities and wavelengths, the variations of dynamic parameters of photochemistry and photopolymerization diffusion are presented.

Development of a Hybrid Photopolymer for Stereolithography

New liquid free radical-cationic hybrid photopolymer, consisting of acrylate-based photocurable resin and epoxy-based photosensitive resin for stereolithography by UV laser was developed. The experiment results indicated that the hybrid photopolymer exhibits advantages of both the acrylate-based photosensitive resin and the epoxy-based photosensitive polymer contained in the hybrid system with relatively high photospeed and low linear shrinkage. Stereolithography parts without obvious distortion were built on the stereolithography apparatus HRPLA- I from this hybrid resin successfully and efficiently.

Polymeric microelement on the top of the fiber formation and optical loss in this element analysis

This paper describes the formation technology of polymeric microlenses self-organized on the fiber top in the limited reaction volume. The loss inserted to the optical coupling channel and their sources was investigated.

Liquid deposition photolithography for submicrometer resolution three-dimensional index structuring with large throughput

Photonic devices increasingly require three-dimensional control of refractive index,but existing fabrication methods such as femtosecond micromachining,multilayer lithography and bulk diffusion can only address a select scale range,are often limited in complexity or thickness and have low throughput.We introduce a new fabrication method and polymeric material that can efficiently create mm^(3) optical devices with programmable,gradient index of refraction with arbitrary feature size.Index contrast of 0.1 is demonstrated,which is 100 times larger than femtosecond micromachining,and 20 times larger than commercial holographic photopolymers.This is achieved by repetitive microfluidic layering of a self-developing photopolymer structured by projection lithography.The process has the unusual property that total fabrication time for a fixed thickness decreases with the number of layers,enabling fabrication 10^(5) faster than femtosecond micromachining.We demonstrate the process by sequentially writing 100 layers to fabricate a mm thick waveguide array.

A wideband sensitive holographic photopolymer

A novel wideband sensitive dry holographic photopolymer sensitized by rose bengal (RB) and methylene blue (MB) is fabricated, the holographic storage characteristics of which are investigated under different exposure wavelengths. The result shows that the sensitive spectral band exceeds 200 nm in visible light range, the maximum diffraction efficiency under different exposure wavelengths is more than 40% and decreases with the decrease of exposure wavelength, the exposure sensitivity is not change with the exposure wavelength. This photopolymer is appropriate for wavelength multiplexing or multi-wavelength recording in digital holographic storage.

The changes of holographic characteristics of photopolymer induced by temperature

The changes of holographic characteristics of photopolymer induced by temperature are studied experi-mentally. The results show that the exposure sensitivity increases with the increase of temperature. Themaximum diffraction efficiency and the final maximum diffraction efficiency increase with the increaseof temperature when the temperature is lower than Tg (glass transition temperature), while they decreasewith the increase of temperature when the temperature is higher than Tg. The effect of the change oftemperature on the saturation refractive index modulation is very weak.

Recent advances in holographic data storage

Nowadays, big-data centers still rely on hard drives. However, there is strong evidence that these surface-storage technologies are approaching fundamental limits that may be difficult to overcome, as ever-smaller bits become less thermally stable and harder to access. An intriguing approach for next generation data-storage is to use light to store information throughout the three- dimensional （3D） volume of a material. Holographic data storage （HDS） is poised to change the way we write and retrieve data forever. After many years of developing appropriate recording media and optical read-write architectures, this promising technology is now moving industriously to the market. In this paper, a review of the major achievements of HDS in the past ten years is presented and the key technique details are discussed. The author concludes that HDS technology is an attractive candidate for big data centers in the future. On the other hand, there are many challenges ahead for HDS technology to overcome in the years to come.