Patent ID: 7583713

Claim:
A laser comprising a unipolar quantum cascade laser including a plurality of adjacent semiconductor multilayer structures arranged in a periodic sequence through which an electron flow can be generated by providing at least two contact points, each of the multilayer structures having an optically active area comprising at least one quantum film structure in which there is at least one upper energy level and one lower energy level for the electrons, between the levels light emitting electron transitions occur, as well as having a transition area comprising a plurality of semiconductor layers through which electrons from the lower energy level of the optically active area pass into the upper energy level of an optically active area of an adjacent semiconductor multilayer structure, which is directly adjacent to the transition area in a direction of electron transport, wherein the electron transitions and the electron transport occur solely in the conduction band of the semiconductor multilayer structures, wherein at least one blocking layer inside the optically active area, which has an uppermost conduction band edge potential that is higher than the uppermost band edge potential of all other semiconductor layers contained inside the semiconductor multilayer structure, is provided in the semiconductor multilayer structure and acts to block electron transport at energies of an initial state of a lasing transition and above thereof and to transmit electrons at energies of a final state of the lasing transition and below thereof and is located at an end of the optically active area in the direction of electron transport directly adjacent to the transition area and solely electrons are involved in charge carrier transport.