16-Wavelength DFB Laser Array With High Channel-Spacing Uniformity Based on Equivalent Phase-Shift Technique

The high accuracy of lasing wavelength spacing is one of the key requirements of a distributed feedback (DFB) semiconductor laser array. However, the nonuniformity of the wavelength spacing is increasingly deteriorating with the increase in the channel number in the laser array. In this paper, theoretical study was made to investigate the effects of sampling pattern deviation and seed grating, as well as waveguide dispersion on the wavelength-spacing uniformity for multiwavelength DFB semiconductor laser arrays (MLAs) fabricated using the reconstruction equivalent chirp (REC) technique. A simple measurement method of dispersion for DFB semiconductor lasers based on the REC technique is also proposed. With the dispersion compensation being included in the sampling period design and small deviation in the seed grating period being guaranteed, a high-channel-count (16-channel) DFB laser array with precise channel spacing of 0.7944 nm/channel (design value of 0.80 nm/channel) was achieved in our experiment. It shows excellent channel-spacing uniformity, and most wavelength residuals are within ±0.10 nm.