Directional optically pumped laterally coupled DFB lasers with circular mirrors

In a previous work, we showed that an adequate choice of phase shifts introduced by defects in a laterally coupled distributed feedback laser (LC-DFB) structure can lead to improved performance. In this paper, we change that optimized structure by adding an in-plane back mirror to the structure, funneling light in only one direction into a single-mode waveguide. We show that a well designed circular grating considerably reduces lateral radiation losses in the back mirror, concentrating light in the front end of the device. We also examine the possibility of converting the in-plane emission at the front end of the device into vertical emission by placing a higher-order grating. Furthermore, we show that side mode suppression ratio (SMSR) of the device can be improved by incorporating a nanotaper.