William Paul Mazotti

Stochastic Characterization and Models to Predict Performance Uncertainty in Photonic Packages

There is considerable uncertainty in the prediction of performance of a system, due mainly to idealizations in geometry, material behavior, and loading history. Uncertainties in geometry can be predicted and controlled using tighter tolerances. However, the models currently used to describe material behavior are mostly deterministic. To predict the coupling efficiency of a photonic system to a greater degree of confidence, stochastic analysis procedures are necessary. As part of such an analysis, the behavior of materials must be stochastically characterized. In this paper, we present extensive experimental data on thermally and UV-cured epoxies, typically used in photonic packages to enable stochastic analysis. We perform dynamic mechanical analysis over a wide frequency and temperature range to determine the viscoelastic behavior of the epoxies. We next derive an analytical description of the time-dependent behavior of a vertical cavity surface emitting laser (VCSEL) array bonded to a substrate. We further characterize the variation in the displacement of the VCSEL array due to the stochastic. viscoelastic behavior of the bond epoxy. We carry out Monte Carlo simulation to predict the uncertainty in the coupling efficiency of a generic photonic package. We finally relate the size of the VCSEL laser array to its ability to achieve the required coupling efficiency.

Stochastic Characterization of Epoxies to Predict Performance Uncertainty of Photonic Packages

There is considerable uncertainty in the prediction of performance of a system mainly due to idealizations in geometry, material behavior, and loading history. Uncertainties in geometry can be predicted and controlled using tighter tolerances. However, the models currently used to describe material behavior are mostly deterministic. To predict the coupling efficiency of a photonic system to greater degree of confidence, stochastic analysis procedures are necessary. As part of this analysis, the behavior of materials must be stochastically characterized. In this paper, we present extensive experimental data on thermally and UV-cured epoxies typically used in photonic packages to enable stochastic analysis. The test data includes the viscoelastic behavior. We present analytical model to obtain the variation in the displacement of the epoxies resulting from its stochastic viscoelastic behavior. We utilize the analytical model to predict the uncertainty in the coupling efficiency of a generic photonic package.Copyright

A Systems Approach for Analyzing Uncertainties in Misalignment of a Fiber-Optic System

Performance of a fiber-optic system depends on the coupling efficiency and the alignment retention capability. The optoelectronic system experiences performance degradation due to uncertainties in the alignment of the optical fibers with the laser beam. The laser devices are temperature sensitive, generate large heat fluxes, are prone to mechanical stresses induced and require stringent alignment tolerance due to their spot sizes. The performance of an optoelectronic system is also affected by many other factors such as geometric tolerances, uncertainties in the properties of the materials, optical parameters such as Numerical Aperture etc. To analyze such a complex system, we need to understand the dependence and inter-relationships between various elements that together make the complex system. In this paper, we develop systematic, formal procedures for identifying the relationships between the critical system level parameters through system decomposition strategies. A novel technique to include the sensitivity of the variables with respect to the functions to assist in the system decomposition is developed. We apply graph partitioning strategies to decompose the system into different subsystems. We also demonstrate system decomposition technique using a simple to implement simulated annealing algorithm. The results of system decomposition using graph partitioning technique and simulated annealing are also compared.Copyright