In the context of guided optics, the authors derive, analytically and geometrically, a rigorous general criterion to design wavelength-insensitive interferometers with mirror symmetry, which are needed for wavelength multiplexing/demultiplexing. The criterion is applied to a practical case, resulting in an interferometer that works on a band wider than 70 nm. © 2005 IEEE.
Tormen, M., & Cherchi, M. (2005). Wavelength-flattened directional couplers for mirror-symmetric interferometers. Journal of Lightwave Technology, 23(12), 4387–4392. https://doi.org/10.1109/JLT.2005.859430