ABSTRACT
This chapter traces the development of diode laser resonators from basic double heterostructure to the complicated designs used for optical integration. In order to set the scene, a brief preliminary discussion is given of diode laser fundamentals; a more detailed account will be found in a recent book. The structure makes use of a light–guiding effect which occurs in double heterostructures and which is commonly used in semiconductor lasers. The emission wavelength of a laser is determined primarily by the band–gap of the active semiconductor. The feedback required to give lasing action is provided by some form of resonant cavity, either using mirrors as in the case of the Fabry-Perot laser, or using a grating as in the case of the distributed Bragg reflector (DBR) and distributed feedback lasers. For single–longitudinal–mode operation of a DBR laser, one grating should have low reflectivity for optimal output coupling and the second grating must have narrow bandwidth and high reflectivity for mode selectivity.
