Single Exciton Optical Gain from Dense Colloidal Quantum Dot Films and Their Optically Pumped Laser Applications

Roh, Kwangdong

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Year:: 2016
Contributor:: Roh, Kwangdong (creator); Nurmikko, Arto (Director); Maris, Humphrey (Reader); Zia, Rashid (Reader); Brown University. Physics (sponsor)
Genre:: theses
Subject:: Colloidal quantum dots; Single exciton optical gain; Auger recombination; Distributed feedback laser; Vertical-cavity surface-emitting laser; GaN distributed Bragg reflectors; Semiconductor nanocrystals
Extent:: xviii, 113 p.
DOI: https://doi.org/10.7301/Z0JM2826

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Abstract:: Colloidal quantum dots (CQDs) have emerged as an etd536cient uorescent material with tunable bandgap across the visible spectrum due to quantum connement effect. Also, studies of optical gain and stimulated emission from the CQDs have been extensively reported. However, fast-decaying non-radiative Auger recombination has been impeding further development of CQDs in the laser applications. Here, in this thesis, optical gain dynamics of our core-shell engineered type-I CQDs have been studied via transient absorption spectroscopy, and optically pumped lasers have been demonstrated as optoelectronic device applications. The role of single exciton states as a dominant optical gain mechanism in densely packed II-VI CQD lms by pump-probe laser spectroscopy has been discussed. Optimizing the Stokes shift and having narrow inhomogeneous broadening of the CQDs play the key role for empowering the single exciton states. Consequently, the single exciton gain regime is accessible without the involvement of the non-radiative Auger process. Bragg grating structures have been incorporated with the CQD gain media to create red, green and blue surface-emitting distributed feedback lasers. A compact solid-state laser whose pulse duration exceeds the Auger decay time has been used as an excitation source. Monochromatic single mode lasing actions at low threshold levels were observed with excellent spatial coherence and conversion etd536ciency. Finally, another type of CQD laser device, vertical-cavity surface-emitting laser has been fabricated using nano-porous(NP)-GaN distributed Bragg re ectors. Closepacked CQD lms were sandwiched between the two NP-GaN/GaN DBRs to achieve ultra-low threshold lasing outputs under the same optical excitation condition. This enabled the realization of the pixelated laser display devices driven by a scanning mirror system.
Notes:: Thesis (Ph.D. -- Brown University (2016)

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Roh, Kwangdong, "Single Exciton Optical Gain from Dense Colloidal Quantum Dot Films and Their Optically Pumped Laser Applications" (2016). Physics Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0JM2826

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Theses and Dissertations for the Physics department.
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