Abstract
We theoretically investigate the optical functionality of a semiconducting quantum ring manipulated by two electrostatic lateral gates used to induce a double quantum well along the ring. The well parameters and corresponding inter-level spacings, which lie in the THz range, are highly sensitive to the gate voltages. Our analysis shows that selection rules for inter-level dipole transitions, caused by linearly polarized excitations, depend on the polarization angle with respect to the gates. In striking difference from the conventional symmetric double well potential, the ring geometry permits polarization-dependent transitions between the ground and second excited states, allowing the use of this structure in a three-level lasing scheme.
Highlights
The THz regime is a narrow region of the electromagnetic spectrum for which practical technologies lack the ability to produce or detect coherent radiation
The formation of a double quantum well (DQW) has only been discussed in quantum ring (QR) subject to exceedingly large in-plane magnetic fields [25]; here we show that DQW
We show that the system of a quantum ring between two gates is a tunable double quantum well
Summary
The THz regime is a narrow region of the electromagnetic spectrum for which practical technologies lack the ability to produce or detect coherent radiation. The above mentioned double quantum well (DQW) structures are realized in heterostructures of alternating semiconductor layers with different band gaps. The shapes of these double well potentials are intrinsic to the specific heterostructure and, while robust, offer limited ability to manipulate the shapes of the potentials without the use of large external fields. A quantum ring (QR) represents the simplest example available for study of such a nonsimply connected system These novel nanostructures have already been shown to exhibit a range of fascinating phenomena, predominantly resulting from the Aharonov-Bohm effect [14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34]. We highlight a significant difference between this double-gated ring system and the conventional DQW, namely that intraband optical transitions between the ground and second excited states are dependent on the polarization angles of incident linearly polarized light
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