Silicon-nitride based micro optical components for optical pickup application

The design and fabrication of micro gratings and polarization beam splitters for potential use in micro optical pickups are presented. Silicon nitride is used as the optical material for its low absorption in the visible wavelength. The micro components are framed by a pop-up poly-silicon mechanism as in the standard surface micromachining technology. The micro grating is a binary phase grating. The diffraction ratio between 4 and 10 can be achieved provided that the duty cycle is between 0.4 and 0.6 and the depth between 455nm and 485nm. For a grating designed for a diffraction ratio of 7, the measured ratio is 8.31.The polarizing beam splitter is a silicon nitride thin film placed at the Brewster angle. The transmittance of the TM mode of a micro polarization beam splitter was measured to be more than 98.50%.