Oleg Prudnikov

High angular tolerant color filter using subwavelength grating

A reflective color filter based on a two-dimensional subwavelength grating is proposed. The filter has been designed by performing numerical simulations and has been fabricated on 5×5 mm2 quartz glass using electron beam lithography. The grating color filter shows reflectance of 74% and spectral width of about 80 nm. Furthermore, it has good angular tolerance, up to ±45°, for unpolarized incident light. By analyzing the reflectance spectral distributions in the band diagram, we found that high angular tolerance is achieved due to the high refractive index contrast of grating structures.

Laser pulse shape dependence of poly-Si crystallization

Poly-Si crystallization mechanism is examined by conducting numerical simulations, combining the thermal diffusion equation with a rigorous coupled wave analysis method. The ripples at the boundary of poly-Si grains are modeled as a grating surface structure. Under laser beam irradiation, the melting front profiles are accurately analyzed by including surface diffraction, polarization of the laser, and laser energy density. For two different lasers, XeCl excimer laser (λ = 308 nm) and Yb:YAG solid state laser (λ= 343 nm), the energy density range at which poly-Si grains are gradually ordered was determined. Furthermore, the energy density window of the Yb:YAG laser is found to be four times larger than that of XeCl laser. On the other hand, the Yb:YAG laser may produce amorphous-Si phase after completing the crystallization process. It is suggested that this amorphous-Si phase could be avoided, if a double pulse laser is used.

P-119: Sub-Wavelength Grating Color Filters for Reflective Displays

Sub-wavelength grating color filters are proposed for use with reflective displays. The color filters are composed of two-dimensional silicon gratings on a quartz substrate. Red, green, and blue color filters of 20mm × 20mm size have been fabricated using electron beam lithography method, and have high angular tolerance of up to ±45 degrees for incident angle of light. Numerical simulations reveal that the high angular tolerance is achieved due to the high contrast of the gratings refractive index.