This paper employs topology optimization to systematically design free-topology loss-engineered slow-light waveguides with enlarged group index bandwidth product (GBP). The propagation losses of guided modes are evaluated by the imaginary part of eigenvalues in complex band structure calculations, where the scattering losses due to manufacturing imperfections are represented by an edge-related effective dissipation. The loss engineering of slow-light waveguides is realized by minimizing the propagation losses of design modes. Numerical examples illustrate that the propagation losses of free-topology dispersion-engineered waveguides can be significantly suppressed by loss engineering. Comparisons between fixed- and free-topology loss-engineered waveguides demonstrate that the GBP can be enhanced significantly by the free-topology loss-engineered waveguides with a small increase of the propagation losses.
© 2012 Optical Society of America
Original Manuscript: July 11, 2012
Manuscript Accepted: September 21, 2012
Published: November 28, 2012
Fengwen Wang, Jakob Søndergaard Jensen, Jesper Mørk, and Ole Sigmund, "Systematic design of loss-engineered slow-light waveguides," J. Opt. Soc. Am. A 29, 2657-2666 (2012)