Abstract
Tunable lasers are essential for medical, engineering and basic science research studies. Most conventional solid-state lasers are capable of producing a few million laser shots, but limited to specific wavelengths, which are bulky and very expensive. Dye lasers are continuously tunable, but exhibit very poor chemical stability. As new tunable, efficient lasers are always in demand, one such laser is designed with various sized CdSe/ZnS quantum dots. They were used as a colloid in tetrahydrofuran to produce a fluorescent broadband emission from 520 nm to 630 nm. The second (532 nm) and/or third harmonic (355 nm) of the Nd:YAG laser (10 ns, 10 Hz) were used together as the pump source. In this study, different sized quantum dots were independently optically pumped to produce amplified spontaneous emission (ASE) with 4 nm to 7 nm of full width at half-maximum (FWHM), when the pump power and focusing were carefully optimized. The beam was directional with a 7 mrad divergence. Subsequently, these quantum dots were combined together, and the solution was placed in a resonator cavity to obtain a laser with a spectral width of 1 nm and tunable from 510 to 630 nm, with a conversion efficiency of about 0.1%.
Highlights
Semiconducting quantum dots have been in use for almost three decades
The commercialization of the Quantum dots (QDs) variant of ultra-high-definition (UHD) televisions opened up a vast market for quantum dots in display technology [1,2], as well as generated a great deal of public interest regarding
Quantum dots (QD) are novel semiconducting materials which possess excitons confined to three dimensions, a typical example being the cadmium–selenide binary alloy (Cd–Se)
Summary
Semiconducting quantum dots have been in use for almost three decades now. they continue to inspire several new researches and applications every day. Quantum dots (QD) are novel semiconducting materials which possess excitons confined to three dimensions, a typical example being the cadmium–selenide binary alloy (Cd–Se). When this type of quantum dot is prepared and placed in a suitable medium as a suspension, it disperses and fluoresces strongly in the visible region, with its fluorescence quantum efficiency comparable to that of the conventional organic laser dyes. They differ starkly because the absorption and re-emission in a dye are a result of the delocalization of the π electronic cloud, whereas in the case of Nanomaterials 2017, 7, 29; doi:10.3390/nano7020029 www.mdpi.com/journal/nanomaterials
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