Non-equilibrium electron heating in inter-subband terahertz lasers.

R. W. Kelsall, P. Kinsler, P. Harrison.

    Institute of Microwaves and Photonics, 
    School of Electronic and Electrical Engineering, 
    University of Leeds, 
    Leeds LS2 9JT,
    United Kingdom.

    Physica E7, 48 (2000).

NOTE: the research for this paper was done by me (P. Kinsler),
      Rob Kelsall's name appears first only because he did the 
      presentation at the conference for which this paper was 
      written.

An ensemble Monte Carlo simulation method has been used to model the
carrier dynamics of optically pumped intersubband lasers. GaAs/AlGaAs
asymmetric (single step) and triple quantum well structures are
studied: both are 4-subband systems designed for intersubband pumping
by a 10.6µmCO2 laser, and for far-infrared emission at 11.7 THz
(25.6µm). The simulations predict population inversion at 77 K for the
asymmetric quantum well, but not at 300 K, whence intersubband
electron-electron interactions cause significant re-distribution of
electron kinetic energies in the 4th subband. However, simulations of
the triple quantum well structure show strong inversion at 77 K, and
marginal inversion at 300 K. The improved performance of the triple
quantum structure in this case is attributed to stronger 3rd-2nd
subband scattering (which depopulates the lower of the two laser
levels) due to an anticrossing of eigenstates, and to reduced energy
re-distribution effects.



Email: Dr.Paul.Kinsler@physics.org