Wideband 20-wavelength 1.3- μ m distributed feedback semiconductor laser array using common holographic exposure

The first experimental realization of a 20-wavelength distributed feedback semiconductor laser array with a λ/4 equivalent phase shift using common holographic exposure in the 1.3-μm wavelength domain is reported. It shows very good linearity in lasing wavelengths with a deviation from −0.5 to 0.45 nm. The threshold currents are between 13 and 17 mA. The side mode suppression ratios are all larger than 40 dB under the bias currents of 70 mA. The slope efficiencies at room temperature are all about 0.4 W/A. However, it only changes the micrometer-level sampling structures while the seed grating is uniform. Therefore, its fabrication cost is low.