Design of photonic bandgap fibers by topology optimization

A method based on topology optimization is presented to design the cross section of hollow-core photonic bandgap fibers for minimizing energy loss by material absorption. The optical problem is modeled by the timeharmonic wave equation and solved with the finite element program Comsol Multiphysics. The optimization is based on continuous material interpolation functions between the refractive indices and is carried out by the method of moving asymptotes.

An example illustrates the performance of the method where air and silica are redistributed around the core so that the overlap between the magnetic field distribution and the lossy silica material is reduced and the energy flow is increased 375% in the core. Simplified designs inspired from optimized geometry are presented, which will be easier to fabricate.

The energy flow is increased up to almost 300% for these cases.