Abstract
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 ( $\kappa $ ). This result in particular, which has important significance to minimize error in fabrication, is confirmed against published experimental data for an ADFB laser.
Highlights
C ONTROLLING the color of light emitted by a laser requires careful design of the resonant cavity used
We find that these aperiodic Distributed feedback (DFB) gratings, which are essentially computer optimized digital holograms, can be inversedesigned to possess multiple defect-like modes analogous to those present in quarter-wave phase shifted gratings
Distributed feedback lasers based on uniform gratings show a mode spectrum with two degenerate modes with identical threshold gain values at the stop band edges [4], which may result in dual color emission
Summary
C ONTROLLING the color of light emitted by a laser requires careful design of the resonant cavity used. Coherent frequency generation requires the photomixing of two lasers in a nonlinear medium to generate spectrally pure light at a sum or difference frequency [1]. By generating both frequencies in the same cavity the common-noise effect will significantly reduce the linewidth of generated light, thereby relaxing phase stability requirements on the laser. Distributed feedback lasers based on uniform gratings show a mode spectrum with two degenerate modes with identical threshold gain values at the stop band edges [4], which may result in dual color emission. Small perturbations to the DFB cavity, such as non-zero
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