A variable-focus fluid lens controlled by an electromagnetic actuator and its characteristics are presented in this paper. The repulsive force between an NdFeB magnet and a solenoid through electromagnetic induction causes deflections in the elastomeric membranes integrated in the lens resulting in a focal-length change. The controllability of the focal length of the fabricated lens with an aperture size of 2 mm was approximately from infinity to 15 mm (with input current of 100 mA). The actuator including the solenoid was carefully designed to avoid thermal crosstalk of the lens fluid and magnet from the electromagnetic induction of the solenoid. The settling time to form a convex shape of the lens membrane was approximately 2.5 ms at an input current of 20 mA.
Aberrations of the concave aspherical microlenses are presented. Microlenses are produced by using betanin sensitized gelatin and 532 nm laser irradiation (2nd Nd:YAG harmonic). Aberrations are analyzed by calculation of the longitudinal spherical aberration and the root mean square RMS spot radius. Three presented microlenses had good image quality for the large F number and the moderate field angle.
We studied focusing properties of 2D square photonic crystal with concavo-concavo boundaries. The photonic crystal is built by air holes in a uniform dielectric. The incident plane wave propagates through a section of the photonic crystal and efficient focusing is observed by finite difference time domain simulations. To analyze the properties of photonic crystal we calculated the photonic band structure and equal frequency contours for TE modes. In our simulation we consider influence of geometry of the concave structures on the focusing properties.
In the Year of Professor Jan Czochralski, we with pleasure review the representative recent works of our group, Optical Single Crystals Group, NIMS, Japan. Our group has been working on the development of novel single crystals for optical applications based on the Czochralski technique. Here, 4 kinds of topics are reviewed. 1st one is ferroelectric fluoride BaMgF_{4} single crystals for UV nonlinear optical applications including quasi-phase matching device fabrications. 2nd one is transparent conductive β-Ga_{2}O_{3} single crystals as semiconductor, which has large band-gap, 4.8 eV, for LED applications. 3rd one is F-doped core-free Y_{3}Al_{5}O_{12} single crystals as a potential new lens material for UV/VUV wavelength region. Last one is superior magneto-optical {Tb_3}[Sc_{2-x}Lu_{x}](Al_{3})O_{12} single crystals for near infrared to visible region, and CeF_3/PrF_3 single crystals for UV region.
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