Leaky optical waveguide for high power applications

We propose a novel optical planar waveguide structure for single-mode operation. The proposed structure has a uniform core and a leaky cladding. The cladding is characterized by a refractive-index profile that increases with the distance from the core. Such a structure supports leaky modes. A careful design can ensure a low leakage loss for the fundamental mode and much higher leakage losses for higher-order modes. With all the high-order modes stripped off, the waveguide supports effectively only the fundamental mode even with a large core. We introduce a class of power-law cladding profiles to demonstrate large-core single-mode operation with the structure. The effects of the profile parameters on single-mode operation are investigated by calculating the leakage losses of the first two modes using the transfer-matrix method. Owing to its large confinement area for single-mode operation, the proposed structure can suppress nonlinear effects effectively and is expected to find applications in the design of high power waveguide lasers and amplifiers.