Advanced grating-based WDM demultiplexer

Abstract

Concave gratings traditionally have been based on the Rowland circle design. A grating design formalism is discussed here that allows greater flexibility than the Rowland circle design. With this formalism, a wavelength division demultiplexer (WDM) may be designed so that the passbands for the output waveguides may be tuned after the demultiplexer has been fabricated. The design considerations for these devices are discussed and are different from the design considerations for Rowland circle gratings. The design of the grating facets is discussed in detail. Experimental results show that facets using light at an angle of incidence that is nominally 45° can become highly efficient due to total internal reflection.