TUNNELING INDUCED TRANSPARENCY - FANO INTERFERENCE IN INTERSUBBAND TRANSITIONS

We report the observation of tunneling induced transparency in asymmet ric double quantum well structures. Resonant tunneling through a thin barrier is used to coherently couple the two upper states in a three l evel system of electronic subbands in a GaAs/AlGaAs structure. This cr eates Fano-type interferences for the collective intersubband excitati ons in the absorption from the ground state, analogous to electromagne tically induced transparency (EIT) in atomic systems. We observe a 50% reduction in absorption between the subband resonances which can be e xplained by taking into account the coherent coupling of the upper sta tes. We analyze the bias dependent absorption spectra and determine th e relevant lifetime broadening and dephasing rates for the transitions . (C) 1997 American Institute of Physics.