INTER-SUBBAND SUPERLATTICE OPTICAL EMITTER AND QUANTUM CASCADE SUPERLATTICE LASER

PROBLEM TO BE SOLVED: To provide an ISB(inter-subband) SL(superlattice) emitter which comprises an almost flat mini band as well as a wave function which is spatially symmetric, and permits independent control of an applied electric field, derred operating wavelength, shape of the wave function, and energy position of the remaining state the mini band. SOLUTION: An RT region of an ISP optical emitter 10 comprises a pre-bias SL, and a plurality of split quantum wells (SPQWs). Here, the SPQW is a quantum well which is divided into a plurality of sub-wells by at least one barrier layer which is so thin that the energy state on upper side and lower side is separated over its natural width, to contribute to different mini bands in respective RT regions. On the contrary, the adjoining SPQWs are jointed each other by another barrier layer of such thickness as the mini band is generated across the RT regions.