Improving both transverse mode discrimination and diffraction losses in a plano-concave cavity

The paper considers the interest in using two apertures rather than one in a plano-concave cavity for improving the discrimination between TEM₀₀ and TEM₁₀ modes while keeping the diffraction losses unchanged or even decreasing them. Such an investigation involves stochastic methods like simulated annealing that can be used if and only if the resonant field computation time is low. Fortunately, a quad-double arithmetic recurrence formula allows to compute round-trip operators faster than any adaptative numerical integrator with the same accuracy.