By a News Reporter-Staff News Editor at Electronics Newsweekly -- According to
news reporting originating from Alexandria, Virginia, by VerticalNews
journalists, a patent by the inventors DeCusatis, Casimer M. (Poughkeepsie, NY);
Jacobowitz, Lawrence (San Jose, CA), filed on May 19, 2012, was published online
on July 16, 2013.
The assignee for this patent, patent number 8485812, is
International Business Machines Corporation (Armonk, NY).
Reporters
obtained the following quote from the background information supplied by the
inventors: "A variety of manufacturing techniques such as hot embossing,
casting, and injection molding have been used to produce optical elements in the
micrometer scale. Of those techniques, injection molding has been found to be
preferable over the others because it allows for high production output rates
with very short processing times. Conventional injection molding of optical
elements, such as lenses, filters or optical waveguides involve the injection of
molten optical materials (typically a polymer) into a moldplate that contains
one or more cavities with predetermined optical patterns to be
replicated.
"After the molten optical material has been injected into the
moldplate cavities, the optical material is cured and the desired optical
element with a predetermined optical pattern (e. g., curvature, diameter, focal
length and the like) is formed inside the cavities of the moldplate. The thus
formed optical element is then extracted from the moldplate using a vacuum chuck
or a similar mechanical apparatus. Removing the newly formed optical element
from the moldplate cavities is often difficult, especially if the optical
material remains adhered to the walls of the cavities. To prevent or minimize
adhesion of the optical material to the moldplate cavities, a conformal coat of
release layer is conventionally applied to the surfaces of the moldplate
cavities. This release layer is generally damaged when the optical element is
removed from the moldplate. Consequently, the damaged release layer is removed,
and a new release layer is applied for the injection molding of a new optical
element. Evidently, the structure of the moldplate cavities is a critical
component in an injection molding system.
"Newer micro and nanometer
optical applications require optical elements with very shallow radius of
curvature and very precise dimensions (e. g., micro-lenses with a radius of
curvature in the order of few hundred nanometers to less than one micron are
highly desirable for applications such as integration of CMOS or CCD digital
cameras in mobile telephones, optical-couplers for solid-state lasers and
photodetectors, launch device elements for optical fiber communications, optical
fiber interconnection, optical waveguides, muxes for WDM, planar lightwave
circuits, photonic devices, and solar cells for electricity generation. However,
high-precision polymer optical components are very difficult to fabricate by the
method of injection molding because very high temperatures are required to melt
the polymer optical material for injection, and at the same time, rapid cooling
of the molten material is desired for efficient mass-production. This fast
change in temperature often causes damage to the cooled polymer and prevents the
proper formation of an optical element with highly precise dimensions. In
addition, other complications of the injection molding process are burning or
scorching of parts due to melt temperature being too high or curing cycle time
being too long; warping of parts due to uneven surface temperature of the
moldplate cavities; surface imperfections and bubbles due to incomplete filling,
surface cracking due to rapid change of temperature, and the like. It is
furthermore a significant economic advantage to enable the attachment of optical
elements directly to optoelectronic devices with lithographic precision at the
wafer-scale or large substrate level in manufacturing of optoelectronic and
optomechanical subsystems.
