Optical control of electric-field poling in LiTaO₃

We present a room temperature technique for optically inducing periodic domain-inverted structures in bulk (0.2mm thick) LiTaO3. By simultaneous application of an electric field and patterned illumination using UV wavelengths (351nm and 364nm) we demonstrate modulation of the resulting domain profile. We discuss the origins of the observed optical effect and describe our results from repeated domain switching, by cycling the electric field

Growth of single and multilayer sesquioxide crystal films for lasing applications via pulsed laser deposition

Sesquioxides, materials of the form RE2O3 (RE: rare earth), are of great interest for lasing applications. These materials offer high thermal conductivities, are mechanically stable, can easily be doped with various rare earth ions and are optically isotropic. Members of the sesquioxide family have the same crystal structure but differing refractive indices, and hence are ideal candidates for multilayer as well as single film growth. Sesquioxides can be challenging to grow from the melt, however, due to their high melting points (>2400 °C)

Influence of light on the coercive field of repoled strontium barium niobate (SBN); the role of secondary repoling

We have found that the application of light to strontium barium niobate (SBN) during electrical repoling stabilises the newly formed domains. This stabilisation becomes apparent when repoling the crystal back into its original domain direction as a change in the distribution of displacement current as a function of voltage. This appears to be the process underlying the other recent work in the area of optical control of domain structures for quasi phase-matching of nonlinear processes. We present an explanation for this effect in terms of the micro-domain structure of SBN. This model should aid in the search for new materials for optical periodic poling

Very high gain single pass two-beam coupling in 'blue' Rh:BaTiO₃

Two-beam coupling has been studied at red and near-infrared wavelengths in "blue" Rh:BaTiO3. High amplification, of the order of 20,000 - 37,000, of a weak signal beam, has been measured. Rh:BaTiO3 exhibits strong intensity-dependent absorption and transmission behaviour and this effect is considered when fitting theoretical plots to the experimental data

Supplemental Lysine and Methionine in Finishing Swine Rations

The term protein requirement does not suffice any longer for the determination of a well balanced ration, and the term amino acid requirement is becoming more standard. Grain and protein feeds vary in their amino acid content and also vary in the availability of the amino acids. When a ration is formulated, the feedstuff amino acid content, amino acid availability and the amino acid requirement of the animal must be considered. These areas, plus amino acid interactions and others, include a broad field and all need extensive clarification. Research has been conducted at several experiment stations to evaluate different protein supplements and crystalline amino acids and their effect on the growth of swine. More amino acid research has been focused on baby and growing pigs, where as very little research has been conducted with finishing pigs

Supplemental Lysine, Methionine, Fat and Fish meal in Swine Growing-Finishing Rations

Quality of supplemental protein in a ration for young pigs is an important consideration when formulating the ration. A good ration for young pigs should have an adequate supply of amino acids, and also the amount of amino acids should be in proper proportion to one another and to the other nutrients in the rat ion. Swine rations formulated without animal protein are usually limiting in lysine and methionine, an addition of lysine and methionine may improve the ration. A previous trial (not published) indicated better pig performance with added lysine, methionine, and fat in the ration. Fish flour, an animal protein source, contains a high percentage of lysine, methionine and other amino acids. This product may be a good source of limiting amino acids, other amino acids, and other nutrients. The objectives of the following experiment were: (1) to study the influence of supplemental lysine, alone, on the performance of growing-finishing pigs, ( 2 ) to study the influence of supplemental lysine and methionine in combination on the performance of pigs, (3) to study the effect of the combination of lysine, methionine and fat on the performance of the growing-finishing pigs, (4) to see if fish flour improved the protein quality of a ration, when fish flour constituted a part of the protein supplement in the diet of a growing-finishing pig

Laser-assisted transfer for rapid additive micro-fabrication of electronic devices

Laser-based micro-fabrication techniques can be divided into the two broad categories of subtractive and additive processing. Subtractive embraces the well-established areas of ablation, drilling, cutting and trimming, where the substrate material is post-processed into the desired final form or function. Additive describes a manufacturing process that most recently has captured the news in terms of 3-d printing, where materials and structures are assembled from scratch to form complex 3-d objects. While most additive 3-d printing methods are purely aimed at fabrication of structures, the ability to deposit material on the micron-scale enables the creation of functional, e.g. electronic or photonic, devices [1]. Laser-induced forward transfer (LIFT) is a method for the transfer of functional thin film materials with sub-micron to few millimetre feature sizes [2,3]. It has a unique advantage as the materials can be optimised beforehand in terms of their electrical, mechanical or optical properties. LIFT allows the intact transfer of solid, viscous or matrix-embedded films in an additive fashion. As a direct-write method, no lithography or post-processing is required and does not add complexity to existing laser machining systems, thus LIFT can be applied for the rapid and inexpensive fabrication or repair of electronic devices. While the technique is not limited to a specific range of materials, only a few examples show transfer of inorganic semiconductors. So far, LIFT demonstration of materials such as silicon [4,5] have undergone melting, and hence a phase transition process during the transfer which may not be desirable, compromising or reducing the efficiency of a resulting device. Here, we present our first results on the intact transfer of solid thermoelectric semiconductor materials on a millimetre scale via nanosecond excimer laser-based LIFT. We have studied the transfer and its effect on the phase and physical properties of the printed materials and present a working thermoelectric generator as an example of such a device. Furthermore, results from initial experiments to transfer silicon onto polymeric substrates in an intact state via a Ti:sapphire femtosecond laser are also shown, which illustrate the utility of LIFT for printing micron-scale semiconductor features in the context of flexible electronic applications

Digital micromirror devices for laser-based manufacturing

Digital Micromirror Devices (DMDs), containing arrays of around one million individually-controllable ~10µm square mirrors, provide an extremely cost-effective and practical method to modulate the spatial beam profile of a pulsed laser source for both additive and subtractive laser processing and printing. When demagnified by a factor of ~100 in one dimension (hence ~10,000 in area) a ~1mJ/cm2 laser pulse reflected from the mirrors on the DMD surface that are switched to the 'on' position, attains a fluence of ~10J/cm2 at the workpiece, which is more than sufficient to ablate most materials of interest to the laser-manufacturing community. More familiar in the context of high values of magnification by the laser projection industry, reversing the role to use them for equally high values of demagnification opens up a wealth of possibilities for ablation, multiphoton polymerization, security marking and fabrication of features that perhaps surprisingly can be well below the wavelength of the laser used. Of key relevance is that very high-resolution patterning can be achieved by a single laser pulse, and step-and-repeat processes, when combined with the refresh rates of the DMD pattern that are currently at the 30kHz level, open up the possibility of processing areas of up to 1cm2 per second with micron-scale resolution where each ~100µm x 100µm area patterned per pulse can display arbitrary pixelated content. We will discuss the application of DMD-baser laser processing to the following areas of interest to the laser-manufacturing community

Laser-induced forward transfer of thermoelectric materials on polymer and glass substrates

Laser-induced forward transfer (LIFT) is a laser-assisted direct write method that has been used to print a range of solids and rheological fluids. The donor that is to be printed is previously deposited onto a transparent support substrate that is usually referred to as a carrier. A highly energetic short-pulsed laser beam imaged through the transparent carrier onto the donor results in the forward transfer of a donor pixel onto a receiver substrate placed either in contact or a few microns apart. Solid films can be transferred with minimal change in their crystal and domain structure via LIFT

Competition and coexistence of multiple mutually pumped oscillations in the visible and infra-red

A photorefractive oscillator. mutually pumped by three wavelengths is presented in various configurations and competition effects demonstrated. The theoretical model used to simulate the behaviour of the oscillation beams is in good agreement with experimental data