DFB laser arrays utilizing CPM-based sampled gratings for precise wavelength control and enhanced single-mode stability

A distributed feedback (DFB) laser array based on the continuous phase modulation (CPM) and sampled grating technique is proposed and experimentally demonstrated. By introducing a discrete phase increment at each sampling period using micrometer-level lithography, an equivalent nanometer-scale continuous phase shift is realized along the cavity. The impact of the total accumulated phase shift and modulation length on the laser characteristics is systematically investigated. Experimental results reveal two distinct operating regimes: the array with even-order phase shifts (CPM-2 Nπ ) exhibits precise linear wavelength detuning with a uniform channel spacing of ∼1.5 nm, behaving analogously to a grating period variation. In contrast, the laser array with odd-order phase shifts (CPM-(2 N +1) π ) demonstrates a wavelength locking effect where the lasing mode is strictly pinned to the Bragg wavelength. Notably, the odd-order configuration utilizes a distributed phase shift mechanism that avoids excessive photon density concentration, resulting in superior single-mode stability with a side-mode suppression ratio (SMSR) exceeding 60 dB. Furthermore, the optimal modulation length is identified to balance field uniformity and mode selectivity. This scheme provides a robust, low-cost solution for fabricating high-precision multi-wavelength laser sources for optical communication systems.