Prism-Coupler Revisited: Analysis and Performance Characteristics Using the Finite-Difference Frequency-Domain Method

The performance of the two-dimensional input prism-coupler configuration for integrated optics applications is analyzed as a function of its critical parameters using the finite-difference frequency-domain (FDFD) method for both TE and TM polarizations. The rigorous FDFD results are compared to the traditional approximate plane-wave-based model developed by Ulrich [R. Ulrich, J. Opt. Soc. Amer., 60, 1337-1350 (1970)] and a modification of it which seems to perform better especially with varying angle of incidence of the exciting Gaussian beam. The FDFD method is formulated for both TE and TM polarizations in conjunction with the uniaxial-perfect-matching-layer absorbing boundary condition as well as with the total-field/scattered-field technique for the incident field implementation. Effective permittivity regularization methods are applied for computational efficiency. The approximate Ulrich´s model generally follows the rigorous results but usually either underestimates or overestimates the prism-coupler´s efficiency and performs worst for the TM polarization.