Lasing by Template-Assisted Self-Assembled Quantum Dots

摘要

Miniaturized laser sources with low threshold power are required for integratedphotonic devices. Photostable core/shell nanocrystals are wellsuited as gain material and their laser properties can be exploited by directpatterning as distributed feedback (DFB) lasers. Here, the 2nd-order DFBresonators tuned to the photoluminescence wavelength of the QDs are used.Soft lithography based on template-assisted colloidal self-assembly enablespattern resolution in the subwavelength range. Combined with the directionalLangmuir–Blodgett arrangement, control of the waveguide layer thickness isfurther achieved. It is shown that a lasing threshold of 5.5 mJ cm~(?2) is reachedby a direct printing method, which can be further reduced by a factor of ten(0.6 mJ cm~(?2)) at an optimal waveguide thickness. Moreover, it is discussedhow one can adjust the DFB geometries to any working wavelength. Thiscolloidal approach offers prospects for applications in bioimaging, biomedicalsensing, anti-counterfeiting, or displays.