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We report the controlled precipitation of PbS quantum dots (QDs) in glasses using multiple irradiation of the femtosecond laser pulses followed by thermal treatment. Upon the irradiation of femtosecond laser, PbS QDs were found to preferentially precipitate in the irradiated area after thermal treatment. Photoluminescence spectra showed PbS QDs in the irradiated area emitted at the long wavelength side, and transmission electron microscope images also confirmed that PbS QDs formed in the irradiated area were larger than those formed in the nonirradiated area. This controlled precipitation of PbS QDs can lead to the development of advanced optical materials.

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We report huge field accumulations in rectangular aperture arrays on thin metal film by using shape resonance in THz frequency region. A huge far-field transmission enhancement is observed in samples of various widths ranging from 10 mum to 1.8 mum which correspond to only an order of lambda/100. Theoretical calculations based on vector diffraction theory indicates 230 times near-field enhancement in case of the 1.8 mum wide rectangular aperture. Transmission measurement through the single rectangular aperture shows that the shape resonance, not the periodicity, is mainly responsible for the transmission enhancement and the corresponding field enhancement.

The authors have demonstrated the second-harmonic generation (SHG) in optical channel waveguides which were fabricated in periodically poled lithium niobate (PPLN) by tightly focused femtosecond laser (781nm) pulses. The measured quasi-phase-matched wavelength and 3dB bandwidth for SHG in a 44.8-mm-long PPLN waveguide which has a domain period of 16.6μm were about 1563 and 0.25nm, respectively. The value of the index difference between the fundamental and harmonic wavelengths in laser written waveguide was inferred to be 0.047.