Intersubband resonance

B. Self-induced transndssion on intersubband resonance in nuiMple quantum wells... 

The quantum cascade laser is very different from the conventional semiconductor laser that has been described in this article, and is based on the intersubband transitions between the excited states of coupled quantum wells, or superlattice structures, and on the resonant tunneling between the wells as the pumping mechanism. This means that lasing action takes place between energy levels within the conduction band (not between the conduction and valance bands). More importantly, since the electron is still in the conduction band, novel bandgap engineering can provide for a transport mechanism that allows for this electron to be reinjected into another set of coupled quantum wells, and is therefore reused. As a result, one injected... 

In this part, we show how ultrashort pulses on resonant intersubband (IS) transitions propagate nonlinearly in multiple symmetric double quantum wells (QWs). A -type modulation-doped multiple QWs sample consisting of N are equally spaced electronically uncoupled symmetric double semiconductor GaAs/AlGaAs QWs with separation d, as shown in Fig. 13. There are only two lower energy subbands contribute to the system dynamics, W = 0 for the lowest subband with even parity and = 1 for the excited subband with odd parity. The Fermi level is below the n = subband minimum, so the excited subband is initially empty. This is succeeded by a proper choice of the electron sheet density. The nonlinear propagation of ultrashort pulses on resonant IS transitions in multiple semiconductor quantum wells is described by the fiill Maxwell-Bloch equations ... 

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