| Author: | Li, Siqi |
| Title: | Design and fabrication of perovskite based frequency-upconverted nano/micro lasers |
| Advisors: | Huang, Haitao (AP) Lei, Dangyuan (AP) |
| Degree: | Ph.D. |
| Year: | 2020 |
| Subject: | Lasers Optical pumping Perovskite Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Applied Physics |
| Pages: | xv, 114 pages : color illustrations |
| Language: | English |
| Abstract: | Frequency-upconverted nano/micro lasers represent a new class of optically pumped laser devices oscillating at energies higher than the pumping photon energies. Taking advantage of the efficient nonlinear optical response of gain materials, such nano/micro lasers can convert infrared pumping radiation to visible lasing output. Perovskite semiconductor materials which have large multi-photon absorption cross-sections are a promising type of gain material for realizing frequency-upconverted laser. Although the research of perovskite materials has recently made remarkable progress in the synthesis, characterization, light-emitting diodes and solar cell devices. There are also some drawbacks which hinder the practical application of perovskite materials in laser device. Firstly, despite numerous papers have reported the lasing of perovskite materials, seldom of them studied the laser performance of perovskites materials during perovskites' growth process. In the first part, we developed a solution method for in situ synthesizing the perovskite micro laser device. Assisted by the anodic aluminium oxide (AAO) template, inorganic perovskite microplates can nucleate and grow on the AAO surface with the size from submicron to tens of micro during the whole growth process. Meanwhile, the two-photon laser performance of the microplate is recorded versus the microplates' growth. It is found a whispering gallery mode (WGM) laser with high quality and low threshold is realized in the microplate. With the size increased, more WGM laser mode appears and the threshold increased, which is consistent with the WGM theory. Our results can help design perovskite microlaser with designed modes, which will promote the application of perovskite materials in laser devices. Secondly, we report a hybrid two-photon random laser device comprising gold nanorods (GNRs)@SiO2 randomly embedded in an all-inorganic perovskite quantum dot (PQD) thin film. With increasing the GNRs@SiO2 distribution density in the PQD film, the hybrid device exhibits an intriguing four-stage transition from amplified spontaneous emission (ASE), incoherent to coherent random lasing, finally to multi-mode incoherent random lasing. By spectrally matching the longitudinal and transverse-localized surface plasmon resonances of the random deposited GNRs@SiO2 array with the two-photon absorption and emission wavelengths of the PQDs, the threshold power density monotonically decreases throughout ASE to coherent random lasing due to double plasmon resonance-boosted population inversion in the PQDs. Frequency upconverted speckle-free imaging has been demonstrated using the plasmonic PQD hybrid device as the illumination source. Our work provides a new strategy of rationally designing plasmonic nanostructures to effectively reduce the threshold power density of the frequency-upconverted random lasing which paves the way for using all-inorganic PQDs in high-efficiency optoelectronic devices, especially, enabling a wide range of real time full-field imaging and projection applications. Finally, to address perovskite laser devices' poor structural stability in a humid environment, we develop a Pb-S covalent bonding approach to synthesize water-resistant perovskite@silica nanodots and keep their emission in water for over six weeks. A two-photon whispering gallery mode laser device made of these ultra-stable nanodots retains 80% of its initial emission quantum yield when immersed in water for 13 h and a random laser device made of the perovskite@silica nanodots can still work after dispersed in the deionized water for fifteen days. These results demonstrate the exceptional robustness of the composite perovskite nanodots. Our synthetic approach opens an entirely new avenue for utilizing perovskite materials in an aqueous environment, which will significantly broaden their applications not only in optoelectronics, but also in bioimaging and biosensing. |
| Rights: | All rights reserved |
| Access: | open access |
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