information:classification, stylistic:tone
Distributed Bragg reflector lasers

A distributed Bragg reflector laser (DBR) is a type of single-frequency laser diode. It is characterized by an optical cavity consisting of an electrically or optically pumped gain region between two mirrors to provide feedback. One of the mirrors is a broadband reflector and the other mirror is wavelength selective so that gain is favored on a single longitudinal mode, resulting in lasing at a single resonant frequency. The broadband mirror is usually coated with a low-reflectivity coating to allow emission. The wavelength-selective mirror is a periodically structured diffraction grating with high reflectivity. The diffraction grating is within a non-pumped, or passive, region of the cavity. A DBR laser is a monolithic single-chip device with the grating etched into the semiconductor. DBR lasers can be edge-emitting lasers or VCSELs. Alternative hybrid architectures that share the same topology include extended-cavity diode lasers and volume Bragg grating lasers, but these are not properly called DBR lasers.