A Theoretical Analysis of the Large Variation in Optical Intensity Caused by Incident Angle Change Around the Critical Angle

We have analyzed the electromagnetic field of an optical system consisting of two uniform dielectric regions of the same refractive index separated by a flat and parallel gap of air/vacuum between them. There exist two input lights toward the gap and two output lights away from the gap. Based on an exact solution for Maxwell's equations, we have investigated the relationship between the two input and the two output lights as a function of the intensity ratio of the two input lights, the phase difference between the two input lights, the incident angle, the refractive index of the two media, and the gap width. We have found the new properties applicable to optical devices with the incident angle close to the critical angle, and several optical modulation schemes have been proposed.