Abstract

The application of Maxwell's equations to the case of light incident upon a plane boundary between an absorbing incidence medium and a nonabsorbing second medium is straightforward. However, the interpretation of the results in terms of reflection and transmission coefficients R and T is clouded by the interference term between the incident and reflected waves. The design of an antireflection (AR) coating for this interface using a single non-absorbing layer follows from the usual solution to the electric field equations by setting the amplitude reflectance equal to zero. In this case, there is no interference term and the interpretation of R and T seems to be clear. In fact, R = 0 and T = 1 as expected. However, it is easy to show using admittance diagrams that this single-layer coating is not an AR coating for light incident from the direction of the non-absorbing medium. Thus, the reflectance from the two sides is not the same. More significantly, the transmittance in the two directions is not the same, seeming to violate the second law of thermodynamics. Calculations are presented for the case that the refractive index of the incidence medium is complex and equal to 1.5-0.5i and the index for the exit medium is 1. Normal incidence and a wavelength of 550 nm are assumed.

© 1990 Optical Society of America