The invention is a system and method for performing all-optical modulation. A semiconductor layer having a defined thickness has an insulator adjacent one surface of the semiconductor. Conductive layers are provided adjacent the semiconductor layer and the insulator. A photodetector is provided to generate an electric field across the conductive layers in response to an input optical gate signal. An input optical signal is modulated by interaction with a plasmon wave generated at the semiconductor/conductive layer interface. By defining the thickness of the semiconductor layer, a desired wavelength of light supports the plasmon waves. Operation of the all-optical modulator requires the provision of an input optical signal of a desired wavelength and the provision of a gate optical signal. An output optical signal is recovered and can be used to store, display or transmit information, for example over a fiber optic communication system, such as a telecommunication system.