Narrow-linewidth 1.3 μm DFB-DCPBH lasers with λ/4-shifted first-order gratings fabricated by electron beam lithography using a new fast resist

1.3 μm DFB-DCPBH lasers were made with λ/4-shifted firstorder gratings fabricated by electron beam lithography using a new fast resist, poly(3-butenyl-trimethylsilane sulfone). The devices had a threshold current of 17 mA, a submode suppression ratio of 39 dB, and a minimum linewidth of 4.4 MHz at 15 mW. By heterodyning two DFB lasers, we obtained a beat frequency of 1.5 GHz with 12 MHz FWHM.