Frozen-Light Modes in 3-way Coupled Silicon Ridge Waveguides

Frozen-light modes supported by the stationary inflection point (SIP) within the pass band of 3-way coupled periodic silicon ridge waveguides is demonstrated. Precise tuning of the coupling between forward and backward propagating modes lead to mode degeneracy with vanishing group velocity. The unit cell is tuned to obtain the SIP on the third branch in the dispersion diagram. Subsequently, we demonstrate a finite structure with 23 unit cells to support the frozen mode at the SIP frequency. For this example, the group velocity at the SIP is 385 times slower than speed of light in vacuum. Transmission resonances of the finite structure, as well as the field distribution within the device at the SIP frequency are studied and presented.