Performance of distributed feedback lasers designed to favor the energy gap mode

Distributed feedback lasers with reflecting ends can support a mode in the energy gap that is exponentially confined to the end reflectors. This mode can become the lasing mode in a laser having one high reflecting and one low reflecting end. We have quantitatively compared the properties of such a laser to more conventional DFB lasers having two uncoated cleaved facets or one uncoated and one low reflecting facet. This comparison required computing a distribution of properties for each laser design because the phases of the two end reflections have random values. The gap mode is inherently compact, and the laser favoring this mode has extremely high single-mode selectivity, excellent quantum efficiency, and good resistance to external reflections, when only one Bragg length long. The conventional laser designs have less mode selectivity and require cavity lengths of about two Bragg lengths to reach their optimum performance.