Computation of cavity resonances by means of adaptive eigenvalues displacement

The numerical computation of resonant frequencies with the associated fields in a three-dimensional cavity is difficult because of the large kernel of the curl operator. In fact, iterative eigensolvers converge toward extremal eigenvalues and remain trapped in the null eigenspace. Displacing the undesired eigenvalues away from zero by adding a complementary eigenproblem allows an effective use of iterative eigensolvers. In this letter an adaptive displacement technique is introduced.