Analysis of distributed-feedback lasers with fractionally organized gratings

We analyze the performance of distributed-feedback lasers with special grating structures. These grating structures consist of subgratings with different lengths (that are integer multiples of a reference length) and/or different phase shifts (that are also integer multiples of a reference phase shift). These grating structures can provide transmission peaks with high quality factors, which may be useful for distributed-feedback lasers. To assess the usefulness of these devices, threshold and steady-state analysis are performed for a few selected examples. A given design example is shown to provide a low threshold without major variations in photon density along the device.