JEOS:RP - Journal of the European Optical Society Rapid publications
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The Legendre transformations in Hamiltonian optics
Get PDFThe Legendre transformations are an important tool in theoretical physics. They play a critical role in mechanics, optics, and thermodynamics. In Hamiltonian optics the Legendre transformations appear twice: as the connection between the Lagrangian and the Hamiltonian and as relations among eikonals. In this article interconnections between these two types of Legendre transformations have been investigated. Using the method of "transition to the centre and difference coordinates'' it is shown that four Legendre transformations which connect point, point-angle, angle-point, and angle eikonals of an optical system correspond to four Legendre transformations which connect four systems of equations: Euler's equations, Hamilton's equations, and two unknown before pairs of equations
Low cost production of computer-generated holograms: from design to optical evaluation
Get PDFIn this work we review some optical characterization methods useful for the low cost production of two phase level computer generated holograms (CGH). As an example, binary CGH are designed with an iterative Fourier transform algorithm (IFTA) and fabricated on a silicon master micromachining with a single step of selective dry etch of silicon dioxide (SiO2) layer. The CGH characterization is performed in three steps; a first one involves the application of spectroscopic ellipsometry measurements to accurately measure the thickness of the SiO2 layer. These results permit the evaluation of the relative complex reflectance between the two levels of the developed hologram as a function of the wavelength. In a second step, interference microscopy is applied to directly visualize the phase shift in the SiO2/Si binary phase profile. Finally, the performance and diffraction efficiency of the fabricated CGH is compared for various lasers with different wavelengths. These experimental measurements in these two last steps confirm with very good accuracy the results derived from the spectroscopic ellipsometry analysis. In conjunction, the combination of these well established optical techniques provides a precise optical characterization of binary diffractive optical elements produced with simple and low cost technique, useful for mass production
Development of the physics of microwaves, and its unification with infrared and optical science
Get PDFRadio waves and light for a long time seemed quite separated, one primarily a field of engineering, and the other more a field of science. Now they have come together, with engineering and basic science strongly involved in both. This change originated largely through the development of microwave physics, which led to laser oscillators and amplifiers. The whole electromagnetic spectrum, from radio waves to the ultraviolet and beyond, now looks like a continuous field from both a scientific and engineering point of view. The development of microwave physics, an essential part of this story, will be discussed here with its impact on masers, lasers, and optics
Fabrication of subwavelength structured surfaces via electrospray deposition of nanobeads
Get PDFThe usability of electrospray deposition (ESD) to form antireflection structured (ARS) surfaces was studied experimentally. Subwavelength structured (SWS) surfaces were produced by depositing nanobeads with diameters of 50 nm onto glass substrates covered with an ITO-Film. The reflectance from the substrates could be decreased about nearly 3% with an onesided ARS surface
Micro integration of optical components for the fabrication of active optical cables
Get PDFOptical interconnects have become very interesting for short reach data transfer. We examine a new concept for integration and miniaturization of such systems based on recent experiments. The application of these designs is an active optical cable. The advantages of the concept and the employed technologies are presented
Matrixes of unconventional micro-optical components molded with etched silicon
Get PDFThis paper reports on a process to create microlenses characterized by unconventional footprints, spherical profiles and a wide range of sizes. Fabricated shapes such as squares, rectangles, ellipses, triangles and hexagons are tested alone as well as in matrix with high fulfill factors. The technique is based on molds from which microlenses are fabricated by UV-molding replication. The molds are produced by silicon wet isotropic etching in an acid solution. The process is mainly steered by temperature and etching concentration. The use of the proposed technology opens a wide range of geometries allowing the fabrication of microlenses matrices with high fulfill factors as well as microlenses for beam-shaping
Investigating the effects of laser beams (532 and 660 nm) in annihilation of pistachio mould fungus using spectrophotometry analysis
Get PDFWhen moulds are illuminated by visible electromagnetic-EM radiations, several effects on nucleus materials and nucleotides can be detected. These effects have a significant influence on mould generation or destruction. This paper presents the effects and implications of a red diode laser beam (660 nm), a second-harmonics of a Nd:YAG laser emitting green beam (532 nm), or the combination of both, on the eradication of Pistachio mould fungus. Incident doses (ID) of both beams are kept identical throughout the experiment. The absorption spectrums of irradiated mouldy samples and the bright-greenish-yellow-fluorescence (BGYF) of fungus occurring in mould texture due to electronic excitation are investigated. We found that a combination of a green and a red laser beam with an ID of 0.5 J/cm^2 provides the optimal effects on Pistachio mould fungus eradication
Modeling of high-index coating lensed fibers for silicon nanophotonic device coupling
Get PDFTwo types of high-index coated lensed fibers are numerically investigated for optical coupling from Si-based nanowire waveguides to the lensed fibers. One is with a layer of high-index film coated on tip of conventional lensed single-mode fiber (SMF) and the other is with an additional coreless fiber section inserted in between. The simulation results show that, for nanowires with mode size diameters ranging from 0.6 to 1.3 µm, the coupling efficiency as high as 80% can be obtained with the former type of fiber when the radius of curvature is around 10 µm and coated with a 5-10 µm thick high-index film. As for the latter design of fiber, an improved working distance is calculated to be as long as 36.8 µm by inserting a coreless fiber section. Both high-index coating lensed SMF designs show potential application for coupling with Si-based nanophotonics
Toward the reflectance measurement of micro components
Get PDFToday, the controls by reflection of optical coatings are most of the time made with flat samples thanks to commercial spectrophotometers. However, components become smaller and more complex, curvature radius of lenses or mirrors are larger, so that measures are not so accurate and sometimes are not possible. Flat samples don’t represent anymore the real reflection ability of the component. So to perform this kind of measurements, special devices are needed. A new means developed by the French Atomic Energy Commission (CEA) is proposed to fill in this gap. This device has a accuracy of 0.06% on flat sample over the 400 nm to 950 nm wavelength range with a spot size of 100 mm. It can measure the reflectance of samples even if their shapes are spherical. We investigate stainless steel balls and optical micro components (mirrors and lens) thanks to the tiny size of the analyzing spot of our reflectometer. Herein we introduce our first results on small optical components and show the limiting factors of our device
Incoherent interaction of nematicons in bias-free liquid-crystal cells
Get PDFWe study experimentally the propagation dynamics and interaction of a pair of mutually incoherent nematicons: spatial optical solitons in nematic liquid crystals. In contrast to earlier studies, we consider a bias-free liquid-crystal cell and compare the soliton interaction in copropagating and counterpropagating geometries. We analyze the dependence of nematicon interaction on input power and observe a direct manifestation of a long-range nonlocal nonlinearity. Attraction of counterpropagating solitons requires higher powers and longer relaxation times than that of copropagating nematicons due to losses-induced power asymmetry of counterpropagating nematicons