Abstract
The sub-micron gratings have been designed, fabricated, and tested. In the grating design, based on the rigorous coupling wave analysis (RCWA), we analyze the relationship between the first order transmission/reflection efficiency and the period of the grating for various shapes as rays pass through the sub-micron gratings. The results show that the diffraction efficiency and diffraction angle strongly depends on the value of the period and its profile. In the grating fabrication, the diamond turning of high-precision imprinting molds and roll-to-roll UV embossing process have the properties of continuous production, high productivity, less manufacturing time, versatility of substrates, and higher imprinting speeds. The diamond turning experiments are conducted to examine the effects of shape design, grating period and cutting speed on machinability of the mold, and the gratings patterned on the light bar are then discussed about the diffraction efficiency and diffraction angle by the optical measurement. In the grating application, the sub-micron gratings are applied for the Liquid Crystal Display (LCD) backlight and the refractive index measuring approach. One problem facing current LCD backlight unit is needed to improve the low efficiency, light illuminance and uniformity by optimizing the structures on the light bar to control the diffraction directions and eliminate the dark region or hot spots in this viewing direction. The first stage is to turn the Red/Green/Blue incident rays into uniformly and normally output white light with high illuminance from the surface of a light guide. The next stage is designed to replace conventional dye color filters for color LCDs. The light bar generates color rays by transmitting them from side-lit color light-emitting diodes (LEDs) through the sub-micron grating. These angular color rays are then redirected using a V-grooved light guide, and converged using a lens array to map to corresponding sub-pixel positions to efficiently display color images. The final application presents the design and simulation results of a high-precision low-cost refractometer that demonstrates the main advantage of a wide measurement range. The proposed design is based on the diffractive properties of sub-micron gratings and Snell’s Law. The precision and uncertainty factors of the proposed system were tested and analyzed, revealing that the proposed refractometer demonstrates a wide measurement range with high measurement accuracy.