Frontiers of Engineering Reports on Leading Edge Engineering from the 1999 NAE Symposium on Frontiers of Engineering (2000) / Chapter Skim
Currently Skimming:
5 Optics
5 Optics
Pages 71-90
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 73... ...
Employing pregrowth calibrations on growth rates periodically with an in situ reflectometer, we obtained a run-to-run wavelength reproducibility for 770- and 850-nm VCSELs of +0.3 percent over the course of more than a hundred runs. These developments have brought VCSEL devices out of the laboratory and into the commercial arena, where they are now available for many advanced technical applications, such as optical communications, biomedical applications, consumer electronics, and optical computing.
|
From page 74... ...
In this paper we demonstrate excellent reproducibility for VCSEL growth employing pregrowth calibrations with an in situ reflectance setup (Breiland and Killeen, 1995; Hou et al., 1996; Kawai et al., 1987) and high material uniformity by optimizing the growth conditions.
|
From page 75... ...
The growth rates achieved by using various alkyl sources were determined from fitting the reflectance waveform with the virtual interface model. The reduction of the growth rate due to an etchback effect of AlGaAs by CC14 with different C doping levels at different temperatures is also extracted from this single calibration run of less than an hour (Hou et al., 1996~.
|
From page 76... ...
Instead, a setting of the gas-flow distribution of 7 percent:78 percept: l5 percent between the inner, middle, and outer injection zones yielded the most uniform thickness. The uniformity, which is most sensitive to the partition setting, was further optimized with the AsH3 flow rate, or the V/III ratio.
|
From page 77... ...
The Al^~OGan^~As ~ unto u.u ~ layer can be selectively oxidized laterally in a steam ambient to form an A1oxide current aperture since the oxidation rate of AlOg~GaOO2As is 3.5 times higher than Ale 92GaO Was (Choquette et al., 1995~. The lasing wavelength and threshold current of VCSEL devices with 9 x 9 Fm2 oxide apertures on both sides of the cavity are plotted in Figure 3 as a function of the distance from the 850 840 830 820 810 \ ~ 800 o-o-° 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Distance from Wafer Center (inches)
|
From page 78... ...
In situ reflectance is used to monitor the growth routinely. With a pregrowth calibration of the growth rate using a test structure periodically, +0.3 percent run-to-run cavity wavelength reproducibility was achieved over a course of about 100 growth runs.
|
From page 79... ...
1995. A virtual interface method for extracting growth rates and high temperature optical constants from thin semiconductor films using in situ normal incidence reflectance.
|
From page 80... ...
1987. Complex refractive indices of AlGaAs at high temperature measured by in situ reflectometry during growth by metalorganic chemical vapor deposition.
|
From page 81... ...
MEMS technology provides a paradigm shift for optics from labor-intensive manual assembly to batch fabrication using integrated circuit-type microfabrication. Compared with conventional optical systems, MEMS optical systems (also called micro-optoelectromechanical systems or MOEMS)
|
From page 82... ...
OPTICAL SYSTEMS ON A CHIP MEMS technology has made it possible, for the first time, to integrate an entire optical table onto a single silicon chip. Optical elements such as lenses, mirrors, and gratings are batch fabricated along with the XYZ stages (micropositioning stages with three independent degrees of freedom)
|
From page 83... ...
o ~ of o ~ o o ~ 8 ~ ~ o e == ~O O ~ 0 ~ .
|
From page 84... ...
The average step size is extremely fine, 20~30 nm, which is ideal for positioning optical elements requiring sub0.1 ,um accuracy. Micro-optical elements can be monolithically integrated with the actuated micromechanical structures.
|
From page 86... ...
The basic building blocks of a MEMS optical crossconnect is illustrated in Figure 4. Under Defense Advance Research Project Agency support, UCLA has been investigating manufacturable, low-cost fiber optic switches using MEMS technology.
|
From page 87... ...
Though this is sufficient for FDDI applications, sub-millisecond switching times and low operating voltages are desired for many other applications. For optical crossconnect applications large mirror areas and low operating voltages are desired.
|
From page 88... ...
Optical crossconnects with a large number of input-output fibers and a very low insertion loss and crosstalk are key components for reconfigurable dense wavelength-divisionmultiplexed optical fiber networks. Recently, an 8x8 MEMS optical crossconnect was demonstrated (tin et al., 1998~.
|
From page 89... ...
1997. Surface-micromachined free-space fiber optic switches with integrated microactuators for optical fiber communication systems.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.