Four-Channel 1.55-μm DFB Laser Array Monolithically Integrated with a 4×1 Multimode-Interference Combiner Based on Nanoimprint Lithography

A monolithically integrated four-channel λ/4 phase shift distributed feedback (DFB) laser array with a 4×1 multimode interference combiner is designed and fabricated using nanoimprint lithography. The threshold currents of the lasers are less than 10 mA, which are as good as a discrete DFB laser. Moreover, the side-mode suppression ratio is also better than 50 dB. The channel space is about 200 GHz for dense wavelength division multiplexing applications in an 1.55 μm system.