Abstract

A monolithic dual-wavelength DFB laser based on four phase-shift (4PS) sampling sections and equivalent chirp technology is proposed and experimentally demonstrated. Dual-wavelength lasing is achieved by introducing two π phase shifts at positions 1/3 and 2/3 along the length of the DFB laser cavity [1]. Compared to conventional sampled Bragg gratings, the 4PS sampling structure has a higher grating coupling coefficient, κ, for the +1^st channel, with κ equal to 0.9 times that of a uniform seed grating [2,3]. Meanwhile, the equivalent chirp technology is applied by linearly modulating the sampling periods along the DFB cavity, thus ensuring the peaks in the photon distributions of the two lasing modes at separate locations along the cavity. Consequently, mode competition between the two modes can be largely suppressed [1]. An electro-absorption modulator (EAM) section is also integrated with the DFB laser to enhance the phase locking between the two lasing modes. Furthermore, the device is based on sidewall grating, which needs only one metalorganic vapor-phase epitaxy (MOVPE) step and one III-V material dry etching step, simplifying the device fabrication process.

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