Abstract
A refractive-index-modulated (RIM) DFB laser, in which the refractive index of the center region of the upper cladding layer of the grating is smaller than that of the side regions, is proposed to obtain an effective λ/4 phase shift in the center region and a distributed coupling coefficient effect simultaneously. Simulation results show that the single-mode gain difference of RIM–DFB lasers is larger than that of corrugation-pitch-modulated (CPM) DFB lasers over the whole range of injection current due to the distributed coupling coefficient effect. The variation of the lasing wavelength of RIM–DFB lasers as a function of injection current is small compared to that of quarter-wavelength-shifted DFB lasers and CPM–DFB lasers. In addition, the effect of the length of the center region of RIM–DFB lasers on the above-threshold characteristics is investigated. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 173–176, 2000.
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