This thesis contains simulation result and experiment result of broken symmetry microlens array designed to increase alignment tolerance in free space optical interconnection. The simulation showed that the broken symmetry lens greatly reduces crosstalk between channels when misalignment exists between optical transmitter and receiver modules. In the simulation, we assumed an optical interconnection scheme consisting of transmitter board and receiver board. In transmitter board light source of VCSEL array is placed at the distance of focal length from microlens array and in receiver board detector array is placed at the distance of focal length from microlens array. The distance between microlenses is thus 2f, which is a confocal system.
The broken symmetry lens array uses a offset lens, making the beam propagation angle different at each channel. Therefore it can reduce the crosstalk between neighboring channels when misalignment exists between transmitter board and receiver board. As a result, we identified the crosstalk is greatly reduced in the presence of misalignment, compared to the result for a symmetry lens array. The propagation of light beam in the lens system was calculated using the Gaussian beam propagation model. We considered a lens configuration with a 250$\mum$ pitch and 200$\mum$ diameter.
We fabricated the microlens arrays using reflowing method. The measured focal lengths were in a range of 990$\mum$ ~1030$\mum$. We experimented one channel of broken symmetry, with power efficiency and crosstalk, because of delay of flip-chip bonding. After measurement, power passing through the first lens is 470$\muw$, and through second lens is 220, when measured input power is 630$\muw$. Power efficiency is calculated as the ratio of power passing through the second lens to input power when using offset lens of 10$\mum$. We obtained 34% of power efficiency through calculation.
In this thesis, we gave demonstrated the broken symmetry lens array...