Summary: Resonant crossover of terahertz loss to gain in a Bloch oscillating InAs/AlSb super- superlattice
and S.J. Allen1, £
Center for Terahertz Science and Technology, University of California, Santa Barbara, California 93106, USA
Agilent Laboratories, 3500 Deer Creek Rd., Palo Alto, CA 94304-1317, USA
Terahertz absorption in waveguides loaded with InAs/AlSb super-superlattice mesas reveals a frequency de-
pendent crossover from loss to gain that is related to the Stark ladder produced by an applied DC electric field.
Electric field domains appear to be suppressed in the super-superlattice comprised of many very short segments
of superlattice, interrupted by heavily doped InAs regions. Resonant crossover is indicated by an increase in
terahertz transmission as the Stark splitting or Bloch frequency determined by the applied DC electric field
exceeds the measurement frequency.
Bloch oscillation was theoretically recognized as a fun-
damental aspect of electrical transport in periodic structures
more than seventy years ago, but only recently have as-
pects of Bloch oscillation been experimentally uncovered
in two quite different systems. Key experiments in semi-