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.
We present recent significant progress in the fabrication of polymer Bragg gratings suitable for telecom applications. We demonstrate that polymer Bragg gratings can be thermally tuned over 20nm with polarization sensitivity less than 0.05nm. Experimental data are presented to address issues of long-term performance stability, propagation loss, polarization sensitivity and practical wavelength tuning. Polymer Bragg gratings are shown to survive very stringent accelerated aging tests and exhibit long-term stability in both material properties and grating performance. The spectral performance of the gratings and example telecom applications employing polymer Bragg gratings are also discussed.
We have designed and fabricated digital thermo-optic switches using low-loss photocuring fluoroacrylate polymers . We have used both modeling and experimental design-rule studies to elucidate the contributions to loss and crosstalk of the various important building blocks that comprise a Y-branch digital optical switch (YDOS). We present herein the results of these studies as well as the achieved performance for 1x2, 2x2 and 4x4 switches fabricated with these designs. Average chip-level insertion loss values for the three designs were 1.1, 1.8, and 2.8 dB, respectively, for 1550-nm illumination. Switching times in every case were below 3 ms. Polarization dependent loss was less than 0.1 dB at 1550 nm. Fully packaged permanently pigtailed versions of the 2x2 and 4x4 switches were also constructed. For these packaged devices, average insertion losses of 2.0 and 3.3 dB were achieved, and crosstalk was maintained at a value less than -45 dB.
A process is described here which is capable of creating very low cost single or multimode waveguides. To reuce the cost of manufacture to the lowest levels, one must move away from intensive individual processing steps such as wafer- based spin coating, lithography, and development. Here, a process is described which is inspired by the printing industry; especially the printing of raised features to form simple, low cost holograms typically used for product security. All efforts must be approached with a level of precision and engineering not typically required in the embossing industry. Precision resist masters of 12' dimension were created using commercially available photoresists and photomasks. High fidelity molds (and embossing tools) were made by replicating the master in both metal and elastomer. PET film was coated with an underclass layer which uniformly reproduced waveguide channel features. The filling process of waveguide cores proceeded through the coating of the channels followed by lamination of an overcoating. Finally, end face preparation was examined through die cutting, slitting, and laser cutting techniques.
We have investigated the photochemistry and optical properties of an azo dye-based electro- optic (EO) copolymer, methacrylate-bound Disperse Red 1/methylmethacrylate (MA1). We present a complete picture of the optical properties of the copolymer at wavelengths ranging from 200 nm to 1800 nm with detection sensitivity over 6 orders of magnitude. We describe intrinsic measurements of absorption loss and also describe how temperature and radiation affect absorption loss. Photochemical investigations reveal details concerning photodelineation of waveguides in MA1. Irreversible photodegradation of the azo chromophore proceeds with both visible and ultra-violet radiation and a quantum yield of 2 X 10-5 is found for 475 nm radiation in MA1.
Practical applications of electro-optic polymers require thermally stable materials with high electro-optic coefficients and low absorption loss. In this report, we first review the properties of some azo-based electro-optic polymer materials and devices. We then describe a new class of electro-optic cardo polymers with glass transition temperatures greater than 200$DEGC.
We report loss measurements in polymer-bound Disperse Red I slab and photodelineated channel waveguides. Losses resulting from electronic charge-transfer and vibrational carbon- hydrogen stretch overtone absorptions, trans to cis isomerization, exposure to visible or ultraviolet (UV) light and changes in dye pendant group number density are investigated. A waveguide absorption spectrometer is described which can measured waveguide losses (alpha) ((lambda) ) from 600 - 1800 nm. Absorption losses are compared to the wavelength dependent electro-optic coefficient r33((lambda) ) and a figure-of-merit r33((lambda) )/(alpha) ((lambda) ) is determined for the material.