Macrae Maxfield

Polymer waveguides and device applications

We have developed highly robust polymers derived from liquid multifunctional acrylate monomers that produce waveguides that offer propagation losses equivalent to planar silica guides. This materials technology enables a variety of high performance thermo-optic devices.

High performance thermo-optic switches based on low-loss acrylate polymers

We design and fabricate digital thermo-optic switches using low-loss photocuring fluoroacrylate polymers. We use both modeling and experimental design-rule studies to elucidate the contributions to loss and cross talk of the various important building blocks that comprise a Y-branch digital optical switch (YDOS). We present the results of these studies as well as the achieved performance for 1×2, 2×2, and 4×4 switches fabricated with these designs. Average fiber-to-fiber chip- level insertion loss (IL) values for the three designs are 1.1, 1.5, and 2.8 dB, respectively, for 1550-nm illumination. Switching times in every case are below 3 ms. Polarization-dependent loss is less than 0.1 dB at 1550 nm. Fully packaged permanently pigtailed versions of the 2×2 and 4×4 switches are also constructed. For these packaged devices, average insertion losses of 2.0 and 3.3 dB are achieved, and cross talk is maintained at a value less than –45 dB. Recent advances in materials performance have now allowed the insertion loss performance to be further improved, with chip-level IL being reduced to 1.0 and 2.2 dB for 2×2 and 4×4 switches, respectively.

Prototyping and validation of thermo-optic planar polymer waveguide devices

Tailored functionality, compactness, and reliability continue to be needed in optical communication devices. Our processes for prototyping and validating low-loss planar polymer waveguide devices can respond rapidly to these needs through the steps described herein. In the past two years we have prototyped several distinct thermo-optic devices and established process- and product-reliability that is broadly applicable. Our prototyping and validation processes consist of modeling, waveguide fabrication for verification of design rules, optical characterization, heater fabrication (for thermo-optic devices), and bare-chip accelerated aging. First, modeling provides insight into optimized designs that can be fabricated with low-loss polymers. These designs are subsequently verified by experiment. Optical building blocks, such as bends, splits, and crossovers, have been characterized, and selected for use in the design of devices for applications such as switching, variable attenuation, and wavelength selection. Resistance heater dimensions and waveguide structures are optimized for maximum thermo-optic effect, minimum response time, and operational stability. As an example, a 2x2 thermo-optic switch, characterized at 1550 nm, has a maximum insertion loss of 1.8 dB, polarization dependent loss less than 0.1 dB, and switching time of less than 3ms. A robust waveguide fabrication process combined with a rapid prototyping ability provides the ability to efficiently evaluate design options. Short term and long term statistical data show that the fabrication process is in good control. Environmental screening tests combined with high temperature aging under various conditions of atmosphere and electrical power provide an efficient means to evaluate materials and processes, estimate product lifetime, and isolate failure mechanisms.

Accelerated aging of tunable thermo-optic polymer planar waveguide devices made of fluorinated acrylates

Planar wave guide device components, made from photocurable fluoroacrylates, demonstrated stability under conditions that exceed those needed to operate planar polymer thermo- optic switches. Fluoroacrylate polymers exhibited negligible decomposition at 200 degree(s)C. Insertion loss and polarization-dependent loss showed no increase at temperatures up to 257 degree(s)C. The reflected spectrum of a Bragg grating showed no monotonic change in (lambda) B, width, or strength in 105 days at 125 degree(s)C. Humidity changes from 0 to 90%RH caused a reversible blue shift in (lambda) B of only 0.00004. Light flux of 130mW exhibited no impact on n, (delta) n, or IL. Heaters showed no degradation at 85 degree(s)C/85%RH. Bonding to substrate, heaters, and pigtails remained intact throughout the testing.