Accelerated solution of the frequency-domain Maxwell's equations by engineering the eigenvalue distribution of the operator.

We introduce a simple method to accelerate the convergence of iterative solvers of the frequency-domain Maxwell's equations for deep-subwavelength structures. Using the continuity equation, the method eliminates the high multiplicity of near-zero eigenvalues of the operator while leaving the operator nearly positive-definite. The impact of the modified eigenvalue distribution on the accelerated convergence is explained by visualizing residual vectors and residual polynomials.