Dual-Frequency Defect-Mode Lasing in Aperiodic Distributed Feedback Cavities

In this letter, we aim to provide the first in-depth study of a multiband hologram filter response under the influence of gain. We find that these aperiodic distributed feedback (ADFB) gratings, which are essentially computer optimized digital holograms, can be inverse designed to possess multiple defectlike modes analogous to those present in quarter-wave phase shifted gratings. We attribute this phenomenon to the interaction between multiple photonic band gaps in ADFB cavities. Further examination of the ADFB gratings reveal that the defect-mode lasing solutions are insensitive to the variations of the grating feedback strength (κ). This result in particular, which has important significance to minimize error in fabrication, is confirmed against published experimental data for an ADFB laser.