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Research paper : A challenge to the low-cost production of highly functional optical elements (J. Nishii)−26−Synthesiology - English edition Vol.1 No.1 (2008) guide panels for liquid crystal displays. The technological level of Japanese molding process, on the other hand, is outstanding in the world. There are plenty of accumulated human resources, facilities, and knowledge. Unfortunately, the products based on the reliable glasses are only micro lens arrays and diffraction gratings with the period over 10 µm. Therefore, the glass devices in the resonance and sub-wavelength range have been an unexplored territory.In this study, several research objectives were set based on the scenario shown in Figure 3, which were fundamental or intermediate technologies to accelerate the development of sub-wavelength optical element using glass-imprinting process. AIST studied the fundamental technologies using the vast amount of research results from the past, such as the development of glass compositions. On the other hand, the three processes including mold fabrication, coating for demolding, and the precision molding process relied heavily on the knowledge of the home appliance companies. Therefore, such works were conducted carefully and strategically while AIST supported the home appliance companies.4 Development of new optical components through integration of elemental technologiesA central laboratory was established in Kansai Center of AIST to integrate the research potentials of home appliance companies, material companies and universities. The former companies install the optical elements fabricated by the molding process in the final products. The latter companies develop several glass materials appropriate for molding process. The universities conduct the advanced simulation research in optics and rheology. Here, it was important that the knowledge of microfabrication and characterization technologies for glasses and ceramics were accumulated within the AIST research group. An example of successful development of optical elements is described in the following sections.4.1 Development of wave plate based on structural birefringence Wave plate is used in the optical disc drive to separate the light traveling from the light source to the disc and the light reflected on the surface of a disc in order to detect the optical signal by the photo diode. The materials for the current wave plate are resin or crystal, which have different specifications depending on the operating wavelength. The next-generation optical disc drive, therefore, requires 3 wave plates depending on the wavelengths between blue and red, which is considered to be an obstruction factor for the downsizing of optical system and the reduction of production cost. Also, as wavelength of the light source shortens, sufficient light resistance is required for the optical elements. The glass wave plate based on the structural birefringence is a promising candidate for overcoming these issues.Optical pickup opticsMedical opticsRobot visionSafety recognitionSecurityImaging opticsPolarization controlDispersion controlReflection controlLight trappingPrecision moldingHybrid control of refractionand diffractionMolding simulation・Finite Element Method (FEM)Optics simulation・Rigorous Coupled Wave Analysis (RCWA)・Finite Difference Time Domain (FDTD) method・Beam Propagation Method (BPM)Glass material development・Higher refraction index・Lower softening point・Higher transmission・Lower environmental loadHeat resistant mold material・Ultra-hard alloy・CeramicsHigh temperature property evaluation・Young’s modulus, Poisson’s ratio・Viscoelastic constant・Friction coefficientPrecision mold technology・Ultra-precise position control・Shorter takt timeDemolding process technology・Sputter method・Ion implant methodMicrofabrication technology・Lithography・Etching・Machining processFig. 3 Scenario to realize the fabrication of sub-wavelength optical elements using molding method

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