Antiphase complex-coupled surface-emitting distributed feedback diode lasers with absorptive gratings

Theoretical analysis of antiphase-type complex-coupled, surface-emitting distributed feedback (CC-SE-DFB) diode lasers with absorptive gratings is presented and discussed. Two different designs are studied: one utilizing a semiconductor-based second-order loss and index grating placed at the metal-semiconductor (p-side) interface, and the other employing a combination of metallic and semiconductor materials for the second-order loss and index grating. For certain design parameters, these two types of absorptive-grating structure are shown to select lasing in the symmetric mode (i.e., orthonormal emission in a single-lobe beam pattern). By comparison to metal-grating surface-emitting devices, the threshold gains for these structures are lower by factor of 3 to 4. For 500-μm-long gratings, the symmetric-mode is favored to lase with threshold gain values as low as 18 cm/sup -1/ and differential quantum efficiency as high as 34%.