Reflectionless tunneling of light in gradient optics.

We analyze the optical (or microwave) tunneling properties of electromagnetic waves passing through thin films presenting a specific index profile that provides a cutoff frequency when the films are used below this frequency. We show that, contrary to the usual case of a square index profile, where tunneling is accompanied by a strong attenuation of the wave due to reflection, such films present the possibility of reflectionless tunneling, where the incoming intensity is totally transmitted.