Characteristic Study Of External Cavity Semiconductor Lasers With Fiber Bragg Grating

Fiber Bragg grating external cavity lasers (FGECL) are essential devices in every field of the optical communications, which is guaranteed for realizing the Automatically Switched Optical Network (ASON) that is easy to be updated and re-configured. This dissertation contains wide research on fiber Bragg grating external lasers including their theory modeling, fabrication and applications. The main parts are as follows:(1) The instability of the FGECL is brought by the phase-shift and the change of the cavity length. Due to the instability of the FGECL, genetic algorithm is used to modify the parameter values of the FGECL for the first time, which can be applied to reduce the effect of the instability by the external optical feedback.(2) The static and dynamic state characteristics of the FGECL as a function of their parameters are discussed theoretically. The research indicates that the instability of the output light in the FGECL can be reduced by the strong coupling efficiency between the fiber grating and the semiconductor chip, and at the same time the high side-mode suppression ratio (SMSR) can be obtained. For maintaining the high SMSR, the lowest limit of the fiber grating reflectivity value and the range of the internal chip length are proposed. It is found that the best way is choosing the fiber grating as the power output facet in this laser. This conclusions are all for the design of the single mode fiber grating external semiconductor lasers.(3) Combination of equivalent reflection cavity model and transmission line theory is successfully applied in theoretical analysis of the tunable external cavity lasers with multi-section. In the laser, the active section, passive section and the grating can be regarded as the transmission line system by that theory modeling, and then the properties such as resonance modes, wavelength tuning, threshold characteristics, output spectra and as well as the SMSR of every output wavelength are analyzed.(4) It is discussed how to used the vernier tuning principle on the wide tunable external cavity lasers. The generation of 21 channels over a maximal tuning range of 16.8nm is allowed, which utilizes the internal refractive index change of the phase section to remove the internal comb-like modes. A reliable fundamental theory is provided for the experimental results published. (5) Owing to the sidelobe effects of the sampled fiber grating, two type of the sampled fiber Bragg grating external cavity semiconductor laser would be studied. It is indicated that the sidelobe has a great influence on the internal resonance modes, the SMSR and the vernier effect. The sinc shape of the reflectivity envelope on the sampled fiber Bragg grating leads to that lasing at different wavelengths in the tuning range has different SMSR. For the design of tunable sampled grating lasers, the flatter envelope of the reflectivity maximal should be obtained.