Devices, structures, and processes for optical MEMS.

摘要

High-precision microlenses have been fabricated utilizing hydrophobic effects and polymer jet printing technology. The lenses are formed precisely at desired locations on a wafer using a polymer jet system in which hydrophobic effects define the lens diameter and surface tension creates a high-quality optical surface. They have 200--1000-mum diameters and 343--7862-mum focal lengths. At 635 nm, wavefront aberrations (measured using a Shack-Hartmann sensor of lambda/100 accuracy) are lambda/5-lambda/80, and the variation in focal length is less than 4.22%. Using WYKO NT3300, the maximum deviation of the surface profile from an ideal circle was measured to be approximately 0.15 mum for most cases (range ∼ 0.05--0.23 mum). The average p-v optical-path-length-difference values were 0.14, 0.25, 0.33, and 0.46 mum for 200 mum-, 400 mum-, 600 mum-, and 1 mm-diameter microlenses, respectively.; Using micromachining techniques, polarization beam splitters (PBS), important optical components to separate the orthogonal TE and TM components of light, have been batch-processed and characterized. The devices were fabricated from thin-film, 2 low-stress silicon nitride membranes and showed excellent performance. Measurements using NANO Deep-UV System showed that the final thickness of the membranes varied from 418.8 to 419.5 nm. Using a WYKO NT3300, the radius-of-curvature of a typical nitride membrane was measured to be 51 m: the membrane is virtually flat. Very good performance has been demonstrated by the new MEMS-PBS structures at 635 nm: extinction ratios (for reflected and transmitted light) of (21dB, 10dB), (21dB, 14dB), and (21dB, 16dB) for single-, double-, and triple-layer systems, respectively with corresponding insertion losses of 3, 10, and 13%.; A new, straightforward, CMOS-compatible, three-mask process is used to fabricate high-performance torsional microscanners driven by self-aligned, vertically offset comb drives. Both the moving and fixed combs are defined using the same photolithography mask and fabricated in the same device layer, a process allowing the minimum gap between comb fingers to be as small as twice the alignment accuracy of the photolithography process. The fabricated microscanners have torsional resonant frequencies between 58 Hz and 24 kHz and maximum optical-scanning angles between 8 and 48° with actuation voltages ranging from 14.1 to 67.2 Vac-rms. The yields on two separate fabrication runs have been better than 70%. To demonstrate an application for these scanners, laser-ablation patterns suitable for ocular cornea surgery have been generated. First, a two-dimensional scanning system has been assembled by orienting, two identical microscanners at right angles to one another. Next, when driven by two 90° out-of-phase 6.01-kHz sine waves, the cross-coupled scanners produce circular patterns having radii fixed by the amplitude of the driving voltage. Then, a small pattern from the surface topography found on a US Roosevelt dime has been chosen and emulated to generate a cumulative ablation pattern that compares favorably with similar emulations reported by earlier researchers who used larger, more-complicated ablation systems. (Abstract shortened by UMI.)