Photonic crystals (PCs) have many potential applications because of their ability to control lightwave propagation. We have investigated the tunable ultrashort electro-optical power divider in two-dimensional PC structures. The power divider composed of a dielectric cylinder in air is studied by solving Maxwell’s equations using the plane wave expansion method and finite-difference time-domain method. The power-splitting mechanism is analogous to that of conventional directional couplers, utilizing coupling between guided modes supported by line defect waveguides. To increase the coupling coefficient of PC coupler, the radius of the rods between two waveguides is reduced. The switching mechanism is a change in the conductance in the coupling region between the waveguides and hence modulating the coupling coefficient and eventually switching is achieved. Such a mechanism of wavelength multiplexing should open up a new application for designing components in photonic integrated circuits.