An aluminum wire-grid polarizer whose period is 0.39 microm has been fabricated on a quartz substrate by electron-beam direct-writing lithography and the lift-off method. By using the s -polarization resonance effect and optimizing structural parameters, characteristics such as a loss of less than 20% and an extinction ratio larger than 1000 have been experimentally obtained at the 0.8- microm -wavelength band. Theoretical analysis is performed and found to be consistent with the experimental results.
We demonstrate a one-color one-beam pumping method for a three-dimensional two-step excitation fluorescent display with Er(3+) -doped ZBLAN glass. A localized green fluorescent spot is obtained by use of a focused pump-light beam at 979 nm. The quantum efficiency of the two-step excitation fluorescence is investigated in a time-dependent analysis and an experiment with a pulsed pump light.
An aluminum-wire grid polarizer fabricated directly on a gallium–arsenide photodiode is used to realize a polarization-selective photodetector. Since all of the light transmitted through the wire grid, including higher-order diffraction components, can be detected at the photodiode and since a resonance of incident electromagnetic waves is utilized, the required grid period can be significantly larger. With a grid period of 600 nm and normal incident light at 715 nm, an extinction ratio of 16 can be obtained both for light detected at the photodiode and light reflected from the surface. If light detected at the photodiode is to be optimized, a higher extinction ratio of 30 and a loss of 30% have been experimentally obtained as well. These experimental results are in good agreement with our theoretical simulation.
Highly efficient Cherenkov-type second harmonic generation is investigated. The waveguide is composed of a KTiOPO4 substrate, a Ta2O5 thin-film core and a SiO2 clad in the strip-loaded configuration. The conversion efficiency strongly depends on the waveguide geometry, and it can be a maximum for a particular Ta2O5 film thickness with a Cherenkov angle of nearly 0°. This maximum efficiency is further increased by narrowing the waveguide width down to 1.8 μm. Consequently, a normalized conversion efficiency of 210%/W cm and a blue second harmonic power of 28 mW were achieved with the 4.5-mm-long waveguide.
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