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Continuous-wave lasing in colloidal quantum dot solids enabled by facet-selective epitaxy

机译：通过面选择性外延实现胶体量子点固体中的连续波激射

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摘要

Colloidal quantum dots (CQDs) feature a low degeneracy of electronic states at the band edges compared with the corresponding bulk material(1), as well as a narrow emission linewidth(2,3). Unfortunately for potential laser applications, this degeneracy is incompletely lifted in the valence band, spreading the hole population among several states at room temperature(4-6). This leads to increased optical gain thresholds, demanding high photoexcitation levels to achieve population inversion (more electrons in excited states than in ground states-the condition for optical gain). This, in turn, increases Auger recombination losses(7), limiting the gain lifetime to sub-nanoseconds and preventing steady laser action(8,9). State degeneracy also broadens the photoluminescence linewidth at the single-particle level(10). Here we demonstrate a way to decrease the band-edge degeneracy and single-dot photoluminescence linewidth in CQDs by means of uniform biaxial strain. We have developed a synthetic strategy that we term facet-selective epitaxy: we first switch off, and then switch on, shell growth on the (0001) facet of wurtzite CdSe cores, producing asymmetric compressive shells that create built-in biaxial strain, while still maintaining excellent surface passivation (preventing defect formation, which otherwise would cause non-radiative recombination losses). Our synthesis spreads the excitonic fine structure uniformly and sufficiently broadly that it prevents valence-band-edge states from being thermally depopulated. We thereby reduce the optical gain threshold and demonstrate continuous-wave lasing from CQD solids, expanding the library of solution-processed materials(11,12) that may be capable of continuous-wave lasing. The individual CQDs exhibit an ultranarrow single-dot linewidth, and we successfully propagate this into the ensemble of CQDs.
机译：胶体量子点（CQD）与相应的块状材料（1）相比，其能带边缘处的电子态简并性低，并且发射线宽窄（2,3）。不幸的是，对于潜在的激光应用，这种简并不能在价带中完全消除，从而在室温下将空穴分布扩散到多个状态中（4-6）。这导致增加的光增益阈值，要求高的光激发水平以实现总体反转（激发态的电子多于基态的电子（光学增益的条件））。反过来，这会增加俄歇复合损耗（7），将增益寿命限制在亚纳秒以下，并阻止稳定的激光作用（8,9）。状态简并性还拓宽了单粒子水平的光致发光线宽（10）。在这里，我们演示了一种通过均匀双轴应变降低CQD中的带边简并性和单点光致发光线宽的方法。我们已经开发出一种合成策略，我们将其称为刻面选择性外延：首先在纤锌矿CdSe磁芯的（0001）刻面上关闭然后再打开壳的生长，生成不对称的压缩壳，该壳产生内置的双轴应变，而仍保持出色的表面钝化（防止缺陷形成，否则会导致非辐射复合损失）。我们的合成使激子精细结构均匀且足够广泛地扩散，从而防止了价带边缘态因热而消失。因此，我们降低了光学增益阈值并展示了来自CQD固体的连续波激光发射，扩展了可能能够进行连续波激光发射的固溶处理材料库（11,12）。单个CQD表现出超窄的单点线宽，我们成功地将其传播到CQD的整体中。

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  • 来源
    《Nature》 |2017年第7648期|75-79|共5页
  • 作者

    Fan Fengjia; Voznyy Oleksandr; Sabatini Randy P.; Bicanic Kristopher T.; Adachi Michael M.; McBride James R.; Reid Kemar R.; Park Young-Shin; Li Xiyan; Jain Ankit; Quintero-Bermudez Rafael; Saravanapavanantham Mayuran; Liu Min; Korkusinski Marek; Hawrylak Pawel; Klimov Victor I.; Rosenthal Sandra J.; Hoogland Sjoerd; Sargent Edward H.;

  • 作者单位

    Univ Toronto, Dept Elect & Comp Engn, 10 Kings Coll Rd, Toronto, ON M5S 3G4, Canada;

    Univ Toronto, Dept Elect & Comp Engn, 10 Kings Coll Rd, Toronto, ON M5S 3G4, Canada;

    Univ Toronto, Dept Elect & Comp Engn, 10 Kings Coll Rd, Toronto, ON M5S 3G4, Canada;

    Univ Toronto, Dept Elect & Comp Engn, 10 Kings Coll Rd, Toronto, ON M5S 3G4, Canada;

    Univ Toronto, Dept Elect & Comp Engn, 10 Kings Coll Rd, Toronto, ON M5S 3G4, Canada|Simon Fraser Univ, Sch Engn Sci, 8888 Univ Dr Burnaby, Burnaby, BC V5A IS6, Canada;

    Vanderbilt Univ, Vanderbilt Inst Nanoscale Sci & Engn, 221 Kirkland Hall, Nashville, TN 37235 USA;

    Vanderbilt Univ, Vanderbilt Inst Nanoscale Sci & Engn, 221 Kirkland Hall, Nashville, TN 37235 USA;

    Los Alamos Natl Lab, Div Chem, Los Alamos, NM 87545 USA|Univ New Mexico, Ctr High Technol Mat, Albuquerque, NM 87131 USA;

    Univ Toronto, Dept Elect & Comp Engn, 10 Kings Coll Rd, Toronto, ON M5S 3G4, Canada;

    Univ Toronto, Dept Elect & Comp Engn, 10 Kings Coll Rd, Toronto, ON M5S 3G4, Canada;

    Univ Toronto, Dept Elect & Comp Engn, 10 Kings Coll Rd, Toronto, ON M5S 3G4, Canada;

    Univ Toronto, Dept Elect & Comp Engn, 10 Kings Coll Rd, Toronto, ON M5S 3G4, Canada;

    Univ Toronto, Dept Elect & Comp Engn, 10 Kings Coll Rd, Toronto, ON M5S 3G4, Canada;

    CNR, Emerging Technol Div, Secur & Disrupt Technol, Ottawa, ON K1A 0R6, Canada;

    Univ Ottawa, Dept Phys, Ottawa, ON K1A 0R6, Canada;

    Los Alamos Natl Lab, Div Chem, Los Alamos, NM 87545 USA;

    Vanderbilt Univ, Vanderbilt Inst Nanoscale Sci & Engn, 221 Kirkland Hall, Nashville, TN 37235 USA;

    Univ Toronto, Dept Elect & Comp Engn, 10 Kings Coll Rd, Toronto, ON M5S 3G4, Canada;

    Univ Toronto, Dept Elect & Comp Engn, 10 Kings Coll Rd, Toronto, ON M5S 3G4, Canada;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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