A surface plasmon resonance based wavelength selector is described. An attenuated total-reflection device can be configured so that the reflected intensity of light is a maximum when the resonance condition is achieved. When the device is illuminated with polychromatic light at a fixed angle, the wavelength at which resonance is achieved shows a transmission maximum. By using an appropriate electro-optic material in the device, the wavelength of maximum transmission can be varied. Numerical results are presented.