PROCEEDINGS ARTICLE | September 18, 2006
Proc. SPIE. 6310, Photonic Devices and Algorithms for Computing VIII
KEYWORDS: Optical components, Reflectors, Diffraction, Optical filters, Holographic optical elements, Silicon, Biosensors, Semiconductor lasers, Head, Diffraction gratings
In this paper, silicon-based micro and subwavelength optical elements based on a free-standing silicon nitride (SiN<sub>x</sub>)
membrane are achieved. These elements, including gratings, microlenses, and holographic optical elements (HOEs), are
designed and used within the visible and infrared regions. These devices can be used as collimators, reflectors, and
wavelength-dependent filters with advantages of simple structure, high efficiency and feasibility to integrate with other
elements into a micro-system chip. In order to demonstrate the advantage of micro-optics of free-standing SiN<sub>x</sub>
membrane type in integration, a miniaturized optical pickup head module based on a stacked micro-optical system is
developed. This module consisted of a laser diode, a reflector, a grating, a holographic optical element, and some
aspherical Fresnel lenses. The novel microoptical system can overcome the problems encountered in other microoptical
systems such as off-axis aberration, lower optical efficiency or durability, integration and even in fabrication. A focal
spot with a FWHM diameter of 3.3 μm is obtained while the diffraction limited full-width at half-maximum (FWHM) is
0.7 μm. To extend the advantage of micro-optics of free-standing SiNx membrane, the subwavelength optical elements
base on guided-mode resonance is also developed. With various Si-based structures, the filter possesses numerous
properties such as variable bandwidths, low sideband, flattop, and etc. They are also applied as biosensors to detect the
hybridization process of bio reaction for their high sensitivity. The results show that micro and subwavelength optical
elements fabricated on Si-based material will be a candidate for emerging silicon micro-photonics.
