Physical Optics Corporation (POC) proposed to demonstrate a novel method of externally modulating light in a waveguide, utilizing the surface plasmon polariton (SPP), a two-dimensional electromagnetic wave confined to a metal-dielectric interface by coupling with quantized charge oscillations. The proposed SPP modulator device is in contact with a waveguide and consists of: (1) a thin dielectric buffer layer; (2) a thin metal film of a few hundred atomic layers; (3) an electro-optic material with voltage-controllable refractive index; and (4) the outer electrode. A prototype modulator will be fabricated on a single mode optical fiber by applying a thin-film deposition of the layers. When the refractive index of (3) is made equal to that of the effective mode index, there is full coupling of evanescent waves to SPPs and consequent complete loss of light from the wavequide, so that modulation is achieved by changes in the applied voltage. Unlike conventional devices, an SPP device can be rugged and low cost, operating at very high frequencies with low insertion losses and no back reflections. The high sensitivity of SPP excitation means that such a modulator can operate at very low voltages. The feasibility of two-dimensional switching and modulation matrices will be studied.
