An active device for dynamic control of the transmission properties has at least one photonic crystal waveguide that has an electrically insulating layer formed within or near the waveguide core and two lateral conductive regions divided by the insulating layer. An alternating voltage signal induces phase and amplitude changes of electromagnetic wave propagating inside the device. Electromagnetic wave signals propagating through two such active photonic crystal waveguide devices may be mixed to produce at least one output signal through interference. Devices having one or more such active photonic crystal waveguides may be utilized as a tunable optical delay line, a tunable optical filter, a switch, or a modulator. A preferred embodiment comprises a photonic crystal waveguide made of a silicon slab with a periodic array of apertures or oxide columns therein, wherein an silicon oxide layer disposed in the waveguide core separates a p-doped region from an n-doped region.