Fabrication of a four-channel monolithic integrated laser array with asymmetric sampled grating lasers

We proposed a multi-wavelength laser array with asymmetric sampled grating lasers that are suitable for mass production. The laser was designed to operate at the first-order reflection of a sampled grating with the aid of an index shifter. Based on the proposal, a four-channel laser array was fabricated with 400 GHz wavelength spacing and its operation at designed wavelengths was demonstrated. An individual laser showed a threshold current of 9-13 mA and a slope efficiency of around 0.21 W A(-1). A high side mode suppression ratio over 44 dB was observed as well. The 3 dB modulation bandwidth was 1.6-4.4 GHz with different current levels. The four-channel laser array was combined into a single optical output in fully monolithic integration in such a way that the passive waveguides were constructed with a Y-branch and butt joint. Its performance showed a degradation only in the slope efficiencies, which was attributed to the division loss of the Y-branch.