Laterally coupled distributed feedback laser fabricated with electron‐beam lithography and chemically assisted ion‐beam etching

The fabrication and optical performance of laterally coupled distributed feedback (LCDFB) lasers were investigated. This device differs from a conventional DFB laser in that the grating does not extend inside the laser ridge; rather, gratings adjacent to a single ridge are used to couple to the fringing fields of the active region. This structure allows the entire laser epilayer structure to be grown in a single step, thus eliminating any regrowth steps. A recent design with 1.5 mm cavity length and chemically assisted ion‐beam etching‐defined ridges and gratings resulted in pulsed single‐mode operation up to 36 mW at 937 nm with as‐cleaved facets. The light‐current characteristic of this device demonstrated a threshold current of 15 mA and a sidemode suppression ratio of greater than 30 dB. The spectral temperature sensitivity was 0.65 A/ °C for this LCDFB. Fabrication processes and optical characterization are discussed.