Lasers with distributed feedback (review)

A review is given of the published literature and the work carried out by the present authors on distributedfeedback lasers, in which optical-frequency electromagnetic oscillations are generated using structures with spatially periodic inhomogeneities (of dimensions comparable with the emission wavelength). Various methods of fabrication of such structures are considered, calculations of the principal physical parameters of distributed-feedback lasers are discussed, and experimental results obtained using various active media and pumping methods are reviewed. Some possible technical applications of such lasers are indicated. Attention is concentrated on thin-film lasers (because more work has been done on them than on other lasers), in which the distributed feedback is achieved by periodic spatial variation of the parameters of an optical waveguide.