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Colloidal-Quantum-Dot Ring Lasers with Active Color Control
Nano Letters ( IF 9.6 ) Pub Date : 2018-01-08 00:00:00 , DOI: 10.1021/acs.nanolett.7b04495 Boris le Feber 1 , Ferry Prins 1 , Eva De Leo 1 , Freddy T Rabouw 1 , David J Norris 1
Nano Letters ( IF 9.6 ) Pub Date : 2018-01-08 00:00:00 , DOI: 10.1021/acs.nanolett.7b04495 Boris le Feber 1 , Ferry Prins 1 , Eva De Leo 1 , Freddy T Rabouw 1 , David J Norris 1
Affiliation
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To improve the photophysical performance of colloidal quantum dots for laser applications, sophisticated core/shell geometries have been developed. Typically, a wider bandgap semiconductor is added as a shell to enhance the gain from the quantum-dot core. This shell is designed to electronically isolate the core, funnel excitons to it, and reduce nonradiative Auger recombination. However, the shell could also potentially provide a secondary source of gain, leading to further versatility in these materials. Here we develop high-quality quantum-dot ring lasers that not only exhibit lasing from both the core and the shell but also the ability to switch between them. We fabricate ring resonators (with quality factors up to ∼2500) consisting only of CdSe/CdS/ZnS core/shell/shell quantum dots using a simple template-stripping process. We then examine lasing as a function of the optical excitation power and ring radius. In resonators with quality factors >1000, excitons in the CdSe cores lead to red lasing with thresholds at ∼25 μJ/cm2. With increasing power, green lasing from the CdS shell emerges (>100 μJ/cm2) and then the red lasing begins to disappear (>250 μJ/cm2). We present a rate-equation model that can explain this color switching as a competition between exciton localization into the core and stimulated emission from excitons in the shell. Moreover, by lowering the quality factor of the cavity we can engineer the device to exhibit only green lasing. The mechanism demonstrated here provides a potential route toward color-switchable quantum-dot lasers.
中文翻译：
具有主动色彩控制功能的胶体量子点环形激光器
为了提高激光应用中胶体量子点的光物理性能，开发了复杂的核/壳几何形状。通常，添加更宽禁带的半导体作为壳，以增强量子点核的增益。该壳旨在以电子方式隔离核心，将激子集中到核心，并减少非辐射俄歇复合。然而，外壳也有可能提供第二个增益来源，从而进一步提高这些材料的多功能性。在这里，我们开发了高质量的量子点环形激光器，它不仅表现出来自核心和外壳的激光，而且还具有在它们之间切换的能力。我们使用简单的模板剥离工艺制造仅由 CdSe/CdS/ZnS 核/壳/壳量子点组成的环形谐振器（品质因数高达 ∼2500）。然后我们检查激光作为光激发功率和环半径的函数。在品质因数 >1000 的谐振器中，CdSe 核心中的激子会产生阈值约为 25 μJ/cm 2的红色激光。随着功率的增加，CdS 壳出现绿色激光（>100 μJ/cm 2 ），然后红色激光开始消失（>250 μJ/cm 2 ）。我们提出了一个速率方程模型，可以将这种颜色转换解释为核内激子局域化与壳内激子受激发射之间的竞争。此外，通过降低腔体的品质因数，我们可以设计该设备以仅呈现绿色激光。这里演示的机制为颜色可切换量子点激光器提供了一条潜在途径。
更新日期：2018-01-08
中文翻译：
具有主动色彩控制功能的胶体量子点环形激光器
为了提高激光应用中胶体量子点的光物理性能，开发了复杂的核/壳几何形状。通常，添加更宽禁带的半导体作为壳，以增强量子点核的增益。该壳旨在以电子方式隔离核心，将激子集中到核心，并减少非辐射俄歇复合。然而，外壳也有可能提供第二个增益来源，从而进一步提高这些材料的多功能性。在这里，我们开发了高质量的量子点环形激光器，它不仅表现出来自核心和外壳的激光，而且还具有在它们之间切换的能力。我们使用简单的模板剥离工艺制造仅由 CdSe/CdS/ZnS 核/壳/壳量子点组成的环形谐振器（品质因数高达 ∼2500）。然后我们检查激光作为光激发功率和环半径的函数。在品质因数 >1000 的谐振器中，CdSe 核心中的激子会产生阈值约为 25 μJ/cm 2的红色激光。随着功率的增加，CdS 壳出现绿色激光（>100 μJ/cm 2 ），然后红色激光开始消失（>250 μJ/cm 2 ）。我们提出了一个速率方程模型，可以将这种颜色转换解释为核内激子局域化与壳内激子受激发射之间的竞争。此外，通过降低腔体的品质因数，我们可以设计该设备以仅呈现绿色激光。这里演示的机制为颜色可切换量子点激光器提供了一条潜在途径。
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