Ultralow Propagation Loss Slot-Waveguide in High Absorption Active Material

A slot waveguide formed by high absorption active material is proposed to reduce the propagation loss for monolithic integration. The low propagation loss is attained by concentrating the optical field inside the low-index slot region without absorption. The simulation results show that the propagation loss at 1.55 μm for the slot waveguide can be as low as 1.5 dB/cm in active material with an absorption coefficient of 3000 cm-1, whereas the optical profile is set to be confined within 650 nm.