Quantum dots (QDs) are highly stable, spectrally well-defined, and engineerable quantum emitters. Their emission energy can be tuned by the growth parameters. QDs can be used for a variety of light sources (classical light source and quantum emitter), such as light emitting diodes, lasers, and single- and entangled-photon sources. Single QD also acts as a single photon source which can be used as a flying qubit source in quantum devices. 

Due to the spherically symmetric emission profile from a single QD, a significant amount of emission intensity from the dots are not collected in QDs based photonic devices. This limits the use of QDs as an active light source. Secondly, most of quantum and classical light sources demand bright photon sources with control over polarization, positioning of these quantum emitters as well switchability of the emission. Therefore, there is need to design such QDs based light sources which have intense, directed, polarization-controlled and switchable emission. 

Towards this goal, we plan to fabricate quantum dots based efficient and controllable light sources using two different routes: (1) Dielectric nanoantenna, and (2) Liquid crystal (LC) based switchable light sources. For this purpose, we synthesized CdSe\CdS core\shell quantum dots by using high temperature chemical bottom-up technique and have natural emission at 627nm. In the next step, we plan to fabricate QDs based planar dielectric nanoantenna and investigate the enhanced, directional, and polarization dependent emission from them. We are especially interested in probing the effects of nearby interfaces in such devices on charge fluctuations and on the emission properties of the quantum dots. For the second class of devices, we first plan to synthesize liquid crystal-quantum dots composites and study their optoelectronic properties. The composite will then be used to realize hybrid QDs-liquid crystal devices. We aim to explore distribution and self-organization of QDs in such devices and the effect of electric field on QD distribution as well as emission. The aim is to realize patterned switchable QD based light crystal light sources. Such sources with low dot density can be used as switchable quantum light sources. This comprehensive experimental work on QDs based efficient light sources can find potential applications in quantum technology, lasing and photonic based communication systems. 

Proposal Defence Committee

• Dr Ata Ulhaq (Supervisor)
• Dr. Nauman Zafar Butt
• Dr Ammar Ahmed Khan

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Meeting ID: 929 9106 9088
Passcode: 006879