Jan M. Minkowski Memorial Lecture in Quantum Electronics: Victor Klimov

Description

Victor Klimov, a fellow at Los Alamos National Laboratory and the director for the lab's Center for Advanced Solar Photophysics, will give a talk on quantum dots as part of the Department of Electrical and Computer Engineering's Distinguished Lecture Series. Reception to follow.

Abstract:

Chemically synthesized quantum dots (QDs) can potentially enable new classes of highly flexible, spectrally tunable lasers processible from solutions [1,2]. Despite a considerable progress over the past years, colloidal-QD lasing, however, is still at the laboratory stage and an important challenge, realization of lasing with electrical injection, is still unresolved. A major complication, which hinders the progress in this field, is fast nonradiative Auger recombination of gain-active multicarrier species such as trions (charged excitons) and biexcitons [3,4]. Recently, we explored several approaches for mitigating the problem of Auger decay by taking advantage of a new generation of core/multi-shell QDs with a radially graded composition that allow for considerable (nearly complete) suppression of Auger recombination by "softening" the electron and hole confinement potentials [5,6]. Using these specially engineered QDs, we have been able to realize optical gain with direct-current electrical pumping [7], which has been a long-standing goal in the field of colloidal nanostructures. Further, we apply these dots to practically demonstrated the viability of a "zero-threshold-optical-gain" concept using not neutral but negatively charged particles wherein the pre-existing electrons block either partially or completely ground-state absorption [8]. Such charged QDs are optical-gain-ready without excitation and, in principle, can exhibit lasing at vanishingly small pump levels. All of these exciting recent developments demonstrate a considerable promise of colloidal nanomaterials for implementing solution-processible optically and electrically pumped laser devices operating across a wide range of wavelengths.