Optical waveguide device for wavelength demultiplexing and waveguide crossing

摘要

A zigzag waveguide device is described that includes at least two optical waveguides converged at a vertex to form a waveguide overlap region. Optical loss in the waveguide overlap region is minimized by including a narrow gap of lower refractive index between the overlap region and each waveguide. This technique is also applied to minimize loss in a region where two optical waveguides cross one another. A mirror or optical filter reflectively couples the two waveguides at the vertex. When the coupling is provided by an optical filter, some range of wavelengths is transmitted out of the zigzag waveguide device, rather than reflected. The transmitted light may be collected by an output waveguide which is wider than the waveguides to minimize loss due to divergence. Light exiting the device may be coupled directly to a photodetector with no intervening optical fiber. In addition, the width of an input waveguide of the zigzag waveguide device is tapered to reduce angular spread of the light in the zigzag device.