Distributed feedback laser with anti-reflection layer

Claim 1

A semiconductor laser having a semiconductor body comprising a substrate of a first conductivity type, a resonant cavity, and a layer structure disposed thereon having at least a first passive layer of the first conductivity type, a second passive layer of the second opposite conductivity type and an active layer located between the first and the second passive layers and having a stripe-shaped active region within said resonant cavity, further comprising a pn junction which can produce, at a sufficiently high current intensity in the forward direction, coherent electromagnetic radiation in said stripe-shaped active region, the first and second passive layers having a smaller refractive index for the radiation produced and a larger band gap than the active layer and the resonant cavity being formed by periodical variation in the effective refractive index in the longitudinal direction and over at least part of the length of the active region, the active region being bounded by end surfaces substantially at right angles to the active region and an anti-reflection layer being provided on at least one of said end surfaces and in direct contact therewith, the second passive layer and the substrate being electrically connected to connection conductors, and the anti-reflection layer consisting of hafnium oxide (HfO 2 ).