Namyoung Ahn1,Clément Livache1,Victor Klimov1
Los Alamos National Laboratory1
Namyoung Ahn1,Clément Livache1,Victor Klimov1
Los Alamos National Laboratory1
Electrically pumped lasers employing solution-processable optical gain media will be a game changer in numerous technological areas including on-chips photonics and electronics, optical communications, lab-on-a-chip devices, displays, and projectors. Colloidal quantum dots (QDs) are a promising class of materials for realizing laser diodes. In addition to being compatible with standard solution-based processing techniques, they feature size-controlled emission energies, low optical-gain thresholds, and high temperature stability of lasing characteristics originating from atomic-like character of electronic states.<br/>Despite their promising characteristics, QDs are difficult lasing materials, especially in the case of electrical pumping. One challenge is fast nonradiative Auger recombination of multicarrier states needed to achieve optical gain. Other challenges include poor stability of QD solids under high current densities required for lasing and unfavorable balance between modal gain produced by a thin electroluminescence (EL) active QD layer and large optical losses in charge injection/transport layers.<br/>Recently, the problem of Auger recombination has been alleviated using continuously-graded QDs (cg-QDs) that exhibit strong suppression of Auger decay.<sup>1</sup> Here we resolve the remaining challenges on a path to a QD laser diode. In particular, we develop “current-focusing” EL devices capable to sustain without damage current densities (<i>j</i>) of more than 1 kA cm<sup>-2</sup>.<sup>2,3</sup> Next, we integrate an ultra-high-<i>j</i> charge-injection architecture with a low-loss Bragg-reflection photonic waveguide which allows us to improve optical field distribution within the device and thereby realize the regime when net optical gain is positive.<sup>4</sup> Finally, we develop devices that exhibit strong edge emitted amplified spontaneous emission (ASE) under electrical pumping. The next important milestone – the demonstration of a QD laser oscillator – can be accomplished by supplementing the developed structures with an optical resonator implemented, for example, as an in-plane distributed feedback grating.<br/>1. J. Lim, Y.-S. Park, V.I. Klimov, <i>Nature Materials</i> <b>17</b>, 42-49 (2018)<br/>2. H. Jung, Y.-S. Park, <u>N. Ahn</u>, J. Lim, I. Fedin, C. Livache, V. I. Klimov, <i>Nature Communications</i>, <b>13</b>, 3734 (2022)<br/>3. H. Jung, <u>N. Ahn</u>, V. I. Klimov, <i>Nature Photonics</i>, <b>15</b>, 643-655 (2021)<br/>4. <u>N. Ahn</u>, Y.-S. Park, C. Livache, J. Du, K. Gungor, J. Kim, V.I. Klimov, <i>Adv. Mater.</i> <b>35,</b> 2206613 (2023)<br/>5. <u>N. Ahn</u>, C. Livache, V. Pinchetti, H. Jung, H. Jin, D. Hahm, Y.-S. Park, V.I. Klimov, <i>Nature</i> <b>617,</b> 79-85 (2023)