RESUMEN
We present a method for achieving single-mode distributed feedback lasing, using photonic bandgaps (PBGs) to suppress degenerate lasing modes. These PBGs arise from direct-Bragg coupling and exchange-Bragg coupling due to a passive waveguide placed in proximity to a uniform-grating-active-waveguide lasing structure. Analytic solutions at lasing threshold for this dual-waveguide, four-port structure reveal a high normalized gain margin (e.g., ΔαL = 0.86) accompanied by a low power flatness (e.g., F = 0.001) along the active region, outperforming the λ/4-shifted DFB laser structure. This single-mode lasing mechanism is compelling for both III/V and III/V-on-silicon platforms.
RESUMEN
This Letter lays the foundation of a new type of distributed feedback (DFB) laser whose optical feedback is due to the evanescent coupling between an active positive-index material (PIM) waveguide and a lossy negative-index metamaterial (NIM) waveguide. Active PIM-NIM coupled-mode equations are presented and solved to characterize the dispersion relation, resonant optical gain, and lasing. The photonic bandgap of this grating-less DFB laser does not depend on a Bragg wavenumber, but depends on the difference between the wavenumbers of the PIM and NIM waveguides; controlling this wavenumber difference allows for single-mode lasing and, ultimately, single-mode broadband lasing.