Lasing by Template‐Assisted Self‐Assembled Quantum Dots

Abstract Miniaturized laser sources with low threshold power are required for integrated photonic devices. Photostable core/shell nanocrystals are well suited as gain material and their laser properties can be exploited by direct patterning as distributed feedback (DFB) lasers. Here, the 2nd‐order DFB resonators tuned to the photoluminescence wavelength of the QDs are used. Soft lithography based on template‐assisted colloidal self‐assembly enables pattern resolution in the subwavelength range. Combined with the directional Langmuir–Blodgett arrangement, control of the waveguide layer thickness is further achieved. It is shown that a lasing threshold of 5.5 mJ cm⁻² is reached by 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 discussed how one can adjust the DFB geometries to any working wavelength. This colloidal approach offers prospects for applications in bioimaging, biomedical sensing, anti‐counterfeiting, or displays.