Phase-shifted Bragg gratings have been extensively implemented in superior in-fiber bandpass filters or wavelength selectors, although high-temperature operation remains a challenge. We propose a phase-shifted type-IIa fiber Bragg grating (PSBG-IIa), which can conduct a notch signal as narrow as 4.8 pm within the stopband. The notch's spectrum and wavelength can be adjusted according to the flexible design of the phase-mask translation. Using the thermal resistance as well as the narrow band notch, the PSBG-IIa is implemented in a distributed Bragg reflector laser structure to demonstrate a single longitudinal mode and single polarization laser output that can stabilize robustly at 500 °C. The results demonstrate that the proposed device qualifies as a high-quality optical regulator, without compromise, in the high-temperature region.