Monolithically Integrated Four-Channel DFB Semiconductor Laser Array With an Equivalent-Distributed Coupling Coefficient

An equivalent-distributed coupling coefficient (EDCC) distributed feedback (DFB) semiconductor laser is proposed, and a four-channel EDCC DFB laser array is experimentally demonstrated. In this paper, the EDCC grating profile is realized by varying the duty cycle of a certain subsection of the whole sampled Bragg grating (SBG) along the laser cavity, instead of the true DCC structure obtained by changing the height of the uniform grating pitch. Moreover, the EDCC grating array can be designed by stepping the sampling period of the SBG and fabricated by combining the conventional holographic exposure with a micrometer-level photolithography on the same wafer. The experimental results show that the uniform channel spacing in the array has been obtained and that the residual of the lasing wavelengths after linear fitting changes in the scope of -0.078 and 0.048 nm. Each laser has good single longitudinal mode operation with the minimum side-mode suppression ratio (SMSR) of about 47.65 dB and the average SMSR of 49.83 dB under the same injection current of 80 mA.