Robert R. Krchnavek

Benzocyclobutene optical waveguides

Single-mode optical waveguides at 1300 nm have been fabricated from the organic polymer benzocyclobutene. This material system utilizes a 535 rmb photodefinable resin for forming the core of the waveguide, allowing the waveguides to be processed in a fashion similar to a negative photoresist. The processing conditions required for the fabrication of single-mode benzocyclobutene optical waveguides are presented. With the measured losses in the waveguide equal to 0.81 dB/cm at 1300 nm, this material system is suitable for use in a variety of optical interconnect applications.<<ETX>>

Laser direct writing of channel waveguides using spin‐on polymers

A focused argon‐ion laser beam (λ=350 nm) is used to fabricate optical channel waveguides on oxidized silicon wafers using a commerically available spin‐on polymer. The polymerization process is photon induced, thus allowing the reaction to occur in a room‐temperature ambient. This allows the fabrication of waveguides on a variety of substrates including those with low melting points. The losses in these waveguides are typically less then 1 dB/cm, making them applicable to a variety of optical interconnect problems. In particular, we demonstrate their use in the fabrication of an optical power tap.

Radiant cured polymer optical waveguides on printed circuit boards for photonic interconnection use

We report a simple technique for patterning channelized optical waveguides on standard electronic printed circuit card material. The technique exploits the abundance of transparent, radiant-curing polymer adhesives in the fiber optics and the dental industries. The process is compatible with standard printed circuit card fabrication processes; hence its applicability to optical interconnection scenarios. We report typical guide losses in the 0.4-0.6-dB/cm range. Measurements were made using an automated noninvasive, nondestructive technique, also briefly described here. Simple structures, such as splitters, bus lines, and 90 degrees bends were fabricated and are described. Optical coupling to the waveguides from packaged devices is also discussed.

Controlled particle growth of silver sols through the use of hydroquinone as a selective reducing agent.

Hydroquinone (HQ) was used as the principal chemical reducing agent to prepare aqueous silver nanocolloids from silver nitrate. The data demonstrate that HQ is unable to initiate the particle growth process on its own, but is able to sustain particle growth in the presence of pre-existing metallic clusters. This unique selectivity is similar to that seen in photographic systems. Data are presented on two different approaches to initiating the HQ growth process. Very low levels of sodium borohydride can be used to form seed particles. Alternatively, the data show that controlled growth can be initiated by exposing the samples to UV radiation, relying on the photoreactivity of hydroquinone to start the process. These results were used to explore the dynamics of very dilute NaBH4 seed particles. They also were used to create nonspherical disk and triangular-plate morphologies directly from solution, without the need for subsequent reformation or template processing.

Direct writing of metal conductors with near-uv light

Deposition of micrometer-scale tungsten, molybdenum and platinum lines with the aid of the uv light from an argon-ion laser was investigated. Tungsten and molybdenum were deposited from their corresponding carbonyls and platinum from an acetylacetonate compound. High-quality metal conductors could be achieved for tungsten and platinum using a combined photolytic and pyrolytic, or “hybrid”, deposition scheme. The resistivity for these two deposited metals was approximately twice the bulk value. For molybdenum the deposition process was fast and dominated by the pyrolysis; the corresponding line resistivity was slightly higher than for the two other metals.

Laser direct writing of aluminum conductors

We report, for the first time, the laser direct writing of high‐conductivity aluminum interconnects from dimethylaluminum hydride (DMAlH). These lines were deposited from this metalorganic gas using a focused deep‐ultraviolet laser beam, and the deposition process was studied as a function of several process parameters. Electrical measurements and Auger electron spectroscopy were used to characterize the quality of the laser‐deposited films.

Bilayer, nanoimprint lithography

Nanoimprint lithography has been shown to be a viable means of patterning polymer films in the sub-100 nm range. In this work, we demonstrate the use of a bilayer resist to facilitate the metal liftoff step in imprinter fabrication. The bilayer resist technology exhibits more uniform patterns and fewer missing features than similar metal nanoparticle arrays fabricated with single layer resist. The bilayer resist relies upon the differential solubility between poly(methyl methacrylate) and poly(methyl methacrylate methacrylic acid copolymer). Evidence is presented that shows the technique has a resolution of better than 10 nm.

Photodeposition rates of metal from metal alkyls

Laser photodeposition of zinc from diethylzinc is experimentally studied. Parametric studies of laser power, intensity, gas pressure, and temperature are evaluated to characterize the deposition process. The results of these experiments verify the trends predicted by a simple theoretical treatment. The investigated deposition process shows contributions from both gas‐phase molecules and adsorbed molecular layers. The ability to control the relative contribution from these two media is demonstrated.

Relaxed-tolerance optoelectronic device packaging

The authors present an approach to single-mode fiber coupling which results in relaxed alignment tolerances during the package assembly process. The authors use a ball lens to couple from the optical device either directly to single-mode fiber (SMF), or indirectly to SMF through a fiber lens. The ball lens is aligned and mounted in the first assembly stage. The lens is aligned and fixed either mechanically or semiactively. In the second stage of assembly, the SMF is aligned so as to compensate for any small misalignments of the ball lens. The authors have achieved coupling efficiencies of 33-40 % with this coupling scheme. It has been used for coupling to standard laser diodes and to near-traveling wave optical amplifiers. Fiber-to-fiber gains of 8.5-10 dB have been achieved with packaged devices. The approach provides some versatility with respect to the placement of passive optical components inside the package. >

Precision fabrication of D-shaped single-mode optical fibers by in situ monitoring

A technique has been developed to locally remove, over a distance of several millimeters of fiber length, the cladding layer of single-mode (at the 1300 nm wavelength) optical fibers with 1 /spl mu/m depth precision by use of mechanical lapping and in situ optical transmission monitoring. A cylinder lap dressed with diamond is used to perform high-pressure mechanical lapping. The in situ monitoring technique is based on the specific different attenuations exhibited by higher order propagating modes (for 633 nm light) as the cylinder penetrates into the fiber. Advantages include relatively rapid overall processing, high lapping rate, good optical surface quality, and 1 /spl mu/m precision. Experimental results are presented and analyzed by an approximate geometrical-optics model. >