The prospect of an inexpensive organic laser which can dynamically alter its lasing wavelength is desirable for a number
of display and communication technologies. In this effort, real-time tuning of the lasing wavelength is accomplished
through the use of colloidal crystals to provide the required reflectivity in an external resonator cavity design in which a
gain medium is sandwiched between a dielectric stack and colloidal crystal. Optical pumping of the gain medium lead to
a lasing peak that corresponded to the stop band of the photonic crystal. By varying the compressive strain placed on the
colloidal crystal, the lasing could be tuned across the photoluminescent spectrum of the gain material. Repeated straining
of the assembly did not appear to alter its proclivity to lase when photo-excited or introduce hysteresis in the lasing
wavelength strain relationship. The fast response of the crystal to compressive strain could lead to pulsed organic lasers
operating at kHz modulation frequencies.
Micro-optical devices are very important in current high-tech consumer items. The development of future products depends on both the evolution of fabrication techniques and on the development of new low cost mass production methods. Polymers offer ease of fabrication and low cost and are therefore excellent materials for the development of micro-optical devices. Polymer optical devices include passive optical elements, such as microlens arrays and waveguides, as well as active devices such as polymer based lasers. One of the most important areas of micro-optics is that of microlens design, manufacture and testing. The wide diversity of fabrication methods used for the production of these elements indicates their importance. One of these fabrication techniques is photo-embossing. The use of the photo-embossing technique and a photopolymer holographic recording material will be examined in this paper. A discussion of current attempts to model the fabrication process and a review of the experimental method will be given.
Integrated optical circuits are an important technology for future high tech products. At present there is great interest in producing polymer based optical circuits. These circuits have a number of potential advantages over current silica/semiconductor based systems. These polymer optical circuits have been used to produce waveguide technology. However in general the production of laser systems for these circuits still depends on older semiconductor technologies. Polymer lasers provide a possible candidate for integrated flexible lasers. Many of the systems demonstrated to date use silica/semiconductor substrates to provide sufficient refractive index variation to provide efficient feedback. A novel alternative to this technology is the holographic distributed feedback (DFB) laser geometry. In this system the lasing material is dispersed in a photopolymer holographic recording material. DFB is then provided by a refractive index structure recorded in the material using holographic techniques. In this paper we discuss a range of holographically recorded feedback geometries and examine the possibility of using this technique to produce organic DFB lasers using non contact holographic patterning.
Many of the next generation of high-tech consumer products will take advantage of the manufacturing advances in micro-optics that we are currently taking place. One of the most important areas of micro-optic research is that of microlens design and fabrication. The importance of this area is perhaps highlighted by the range of competing fabrication technologies. Each having important advantages/disadvantages for a given application. It is therefore important to pursue other possible fabrication methods. In this paper we examine two of these novel fabrication techniques: (1) Photo-embossing in holographic recording materials, and (2) Microfluidic lens fabrication. The first of these techniques offers the possibility of combining the advantages of diffractive optical elements with those of conventional refractive optical elements. The second technique in combination with inkjet deposition technology can be used to produce a wide range of optical elements (lenses) and offers the possibility of controlling the lens profile in real time during formation using electric fields.
Many new high-tech consumer products that are now under development require micro-optical elements. The development of these micro-optical devices has been carried out by many different researchers working in a variety of areas. This has lead to a large number of different fabrication techniques. We examine a novel fabrication technique that may allow the development of large arrays of elements quickly and cheaply. It is known that the exposure of dye sensitised Acrylamide layers to light can lead to material refractive index and volume changes. It is therefore proposed that a patterned exposure can be used to form a mixture of volume and surface relief patterning, enabling the production of optical elements. The examination of this fabrication technique, in particular the study of the processes that result in this volume change, may also lead to improvements in the photopolymer material so as to control shrinkage of these materials. The development of low shrinkage holographic recording materials is an active area in holography as most current photopolymer materials exhibit some volume change during the recording process. This has implications for the fidelity of the replayed image. This is of crucial importance in areas such as data storage systems. The further study of this process also has implications for the wider holographic research community. It is important to understand the surface relief profile of the holographic element prior to extracting grating parameters as surface relief effects may influence the experimental data. In this paper we describe initial experimental attempts to produce micro-optical elements for use in the visible spectrum using patterned exposure of an Acrylamide based photopolymer material.
The non-local model assumes that monomer molecules are polymerised to form polymer chains and that these chains are not constrained to the illuminated regions, i.e. they are non-local. A non-local response function was added to account for this non-local effect.
In this paper the generalised model previously published by the authors was further extended to allow for non-linear proportionality to the recording illumination. The resulting equations are presented in this paper. The two harmonic analytic formulae for this extended generalised response function model are also presented in this paper.
Substrate-mode gratings are used to couple and influence the signals that propagate in planar-integrated optical systems. Volume holograms are especially well suited for this role because they allow the recording of slanted fringe gratings. Photopolymer are among the best candidates for such applications due to easy handling, dry development process, high diffraction efficiency and replication possibilities. In this paper, we investigate the recording dynamics of OmnidexTM photopolymer from DuPont. We use the theoretical diffusion model proposed by Zhao and Mouroulis in order to simulate the recording process. Two different experiments are described that lead to the quantitative determination of kinetic parameters in this material. These values are introduced in the diffusion model and different recording procedures are simulated. The conclusion shows that it could be valuable to let the material in the dark for several minutes before develop it. This investigation should improve the understanding of recording process and consequently it should permit to build more efficient components.
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