A novel concavely apodized (CA) distributed feedback (DFB) semiconductor laser was theoretically analyzed and experimentally demonstrated. The CA grating profile is equivalently realized by changing the duty cycle of the sampling structure along the cavity in the middle of which an equivalent phase shift is also inserted. Because the basic grating (seed grating) is uniform, only a common holographic exposure and a µm-level photolithography are required. Therefore, the fabrication cost is highly reduced compared with the true CA grating whose index modulation continuously changes along the cavity. The experimental results show that the laser has good single longitudinal mode operation.