Cost-effective packaging of laser modules using LTCC substrates

The modeling, realization and characterization of photonic module based on the use of Low Temperature Co-fired Ceramics (LTCC) technology is reported. The 3D modeling of the system provides possibility to optimize structures, materials and components in order to achieve optimal performance for the final product and still maintain reasonably low fabrication costs. The cost-effectiveness in the product can be further optimized using an iterative optimization process, in which the effect of module manufacturing tolerances and assembly process tolerances is simulated by a VisVSA Monte-Carlo simulation. The tolerance distributions produced by a VisVSA simulation are used as input parameters together with optical component tolerances in an ASAP Monte-Carlo simulation, in which the final module optical performance distribution in simulated production is obtained. The module cost, performance and optical performance limited yield is possible to define with this iterative process. As an example of this kind of packaging modeling, we present a demonstrator module having a high-power multimode laser diode with a 1mum x 100mum emitting area coupled to a 62.5/125mum graded-index (NA=0.275) multimode fiber. The tolerance modeling results are verified by experimental characterization of the packaged prototypes. Measured coupling efficiencies were in good agreement with simulated ones, when the fiber NA was 0.2 or larger. The measured coupling efficiency, however, was 38% lower than simulated, when the fiber NA was 0.12. This was probably due to the laser mode structure difference between simulation model and reality. Coupling efficiency of 0.46 was obtained in a passively aligned demonstrator module, when the nominal value was 0.48.