Roadmap on holography

From its inception holography has proven an extremely productive and attractive area of research. While specific technical applications give rise to 'hot topics', and three-dimensional (3D) visualisation comes in and out of fashion, the core principals involved continue to lead to exciting innovations in a wide range of areas. We humbly submit that it is impossible, in any journal document of this type, to fully reflect current and potential activity; however, our valiant contributors have produced a series of documents that go no small way to neatly capture progress across a wide range of core activities. As editors we have attempted to spread our net wide in order to illustrate the breadth of international activity. In relation to this we believe we have been at least partially successful

Estudio y caracterización de nuevas emulsiones de haluro de plata como materiales de registro holográfico

One of the most interesting techniques for the production of holographic optical elements is silver halide sensitised gelatin (SHSG). It combines the high sensitivity of photographic emulsions with the well-known low scattering and high diffraction efficiencies corresponding to dichromated gelatin. In this work we made a comparative study on SHSG holograms recorded on three different red sensitive emulsions: Agfa 8E75 HD, Slavich PFG-01 and BB-640 . The influence of the degree of hardening of the gelatin and the size and concentration of silver halide grains in the SHSG proccess is studied. And we will show that real high diffraction efficiencies can be obtained when using BB-640 and Slavich PFG-01 plates for recording phase transmission holograms (as high as 93% for PFG-01 and 90% for BB-640, allowing for reflections). Our investigations reveal that PFG-01 and BB-640 emulsions are not only a substitution to Agfa material, but may offer better results at a moment in which Agfa has stopped its production of holographic material.<br><br>Una de las técnicas más interesantes para la obtención de elementos ópticos holográficos es la gelatina sensibilizada de haluro de plata (GSHP). Esta técnica combina la alta sensibilidad de las emulsiones fotográficas con los conocidos altos rendimientos en difracción y bajos niveles de scattering correspondientes a la gelatina dicromatada. En este trabajo se ha hecho un estudio comparativo sobre hologramas en gelatina sensibilizada de haluro de plata registrados en tres emulsiones diferentes sensibles al rojo: Agfa 8E75 HD, Slavich PFG-01 y BB-640. En dicho estudio se ha analizado la influencia del grado de endurecido de la gelatina y la concentración y el tamaño de los granos de haluro de plata en el procesado GHSP. Se obtuvieron rendimientos en difracción realmente altos cuando se utilizaron las placas BB-640 y Slavich PFG-01 para el registro de hologramas de fase por transmisión (tan altos como el 93% para las PFG-01 y el 90% para las BB-640, después de haber corregido los resultados teniendo en cuenta las reflexiones en las distintas superficies de separación de la placa). Nuestras investigaciones indican que las emulsiones BB-640 y Slavich PFG-01 pueden cubrir el vacío dejado por las placas Agfa 8E75 HD, e incluso pueden ofrecer mejores resultados en un momento en el cual Agfa ha dejado de fabricar material para aplicaciones en Holografía

Analytical approximations for the period of a nonlinear pendulum

This paper deals with the non-linear oscillation of a simple pendulum and presents an approach for solving the non-linear differential equation that governs its movement by using the harmonic balance method. With this technique it is possible to easily obtain analytical approximate formulas for the period of the pendulum. As we shall see, these formulas show excellent agreement with the exact period calculated with the use of elliptical integrals, and they are valid for both small and large amplitudes of oscillation. The most significant feature of the treatment presented is its simplicity because for the level of approximation considered in this paper the required work can be done “by hand”

Linear response deviations during recording of diffraction gratings in photopolymers

In a holographic recording is advisable that the diffraction efficiency increases linearly with the exposure in a wide zone of the curve of diffraction efficiency versus energetic exposure and the slope of the curve must be approximately constant before saturation in order to improve the energetic sensitivity and to get reproducibility in different recordings with the same kind of photopolymer, although to find examples of deviations to this behavior it is usual. The more important deviation experimentally observed in photopolymers with high thickness happen when the first maximum in the curve is lower than the second one. This effect is opposed to an overmodulation. We present a main hypothesis related to the dye concentration into the layer and with the molecular weight of the polymer chains generated in the polymerization process in order to explain this effect.This work was supported by “Ministerio de Ciencia e Innovación” (FIS2008-05856-C02-01, FIS2008-05856-C02-02) and “Generalitat Valenciana”, Spain (GVPRE/2008/274)

El campus virtual y la adecuación a los créditos ECTS

La integración del sistema universitario español en el Espacio Europeo de Educación Superior (EEES) implica la aceptación de un nuevo modelo educativo basado en el trabajo y en el aprendizaje del alumnado. Por tanto, la importancia de la docencia directa por parte del profesorado se reduce considerablemente ampliando su dedicación a organizar, orientar y supervisar el trabajo del alumnado. Las nuevas tecnologías serán importantes en el EEES ya que fomentarán la realización de tareas de aprendizaje deslocalizadas y en un marco horario más flexible que el actual. Cualquier aspecto docente es susceptible de integrarse en el entorno del campus virtual de la Universidad de Alicante (CVUA). Sin embargo, el éxito o fracaso de esta reforma estará en función de que, por una parte, el alumnado asuma el papel activo que le concede el nuevo modelo educativo y de que, por otra, la administración dote de los recursos necesarios para llevar a cabo este proceso. En esta contribución presentamos un conjunto de actividades, implementadas en el CVUA, que permitirán adecuar nuestras asignaturas a la estructura de los créditos europeos. El profesorado que compone el grupo de trabajo ha desarrollado acciones docentes encaminadas a la adaptación de las asignaturas al sistema de créditos europeos.SIN FINANCIACIÓNNo data 200

Optimization of a 1 mm thick PVA/acrylamide recording material to obtain holographic memories: method of preparation and holographic properties

Information holographic storage is a very promising technique due to its high theoretical capacity. One of the key factors in developing holographic memories is the need for a suitable recording material which must have certain specific characteristics. In particular, in order to achieve a high storage density it is necessary to work with great thicknesses. One of the essential requirements for holographic memories to be competitive is that the material must have a thickness of 500 μm or more, but it is not easy to find such thicknesses with the photopolymers currently available. In this study, we develop a method of preparing layers of a polyvinyl alcohol/acrylamide based photopolymer approximately 1 mm thick. Optimization of this material makes it possible to obtain good results for the main holographic parameters; diffraction efficiency 70% and energetic sensitivity 50 mJ/cm2.This work was supported by the Ministerio de Ciencia y Tecnología, CICYT, Spain, under project MAT2000-1361-C04-04