We report long-life GaAlAs lasers showing fundamental-mode high-power operations, which have been developed by providing current blocked nonabsorbing mirror (NAM) regions in the conventional buried twin ridge substrate (BTRS) structure. Suppression of the mirror degradation due to local heating for the NAM and use of the loss-guide mechanism for the BTRS structure are the main cause of the excellent operations. For the fabrication, use of a substrate having a mesa on it and a hybrid epitaxial technique of LPE and MOCVD is an essential point. As a result we have obtained the stable fundamental spatial mode operations up to 120 mW and the maximum output power of 300 mW under a CW operation. Degradation has been insignificant for 6000 hours under the output power of 100 mW and the temperature of 50°C.