Colloidal quantum dots lasing and coupling in 2D holographic photonic quasicrystals.

Global research on the solution-processable colloidal quantum dots (CQDs) constitutes outstanding model systems in nanoscience, micro-lasers, and optoelectronic devices due to tunable color, low cost, and wet chemical processing. The two-dimensional (2D) CQDs quasicrystal lasers are more efficient in providing coherent lasing due to radiation feedback, high-quality-factor optical mode, and long-range rotational symmetry. Here, we have fabricated a 2D quasicrystal exhibiting 10-fold rotational symmetry by using a specially design pentagonal prism in the optical setup of a simple and low-cost holographic lithography. We developed a general analytical model based on the cavity coupling effect, which can be used to explain the underlying mechanism responsible for the multi-wavelength lasing in the fabricated 2D CQDs holographic photonic quasicrystal. The multi-wavelength surface-emitting lasers such as λ0 = 629.27 nm, λ1 = 629.85 nm, λ-1 = 629.06 nm, λ2 = 630.17 nm, and λ-2 = 628.76 with a coupling constant κ = 0.38 achieved from the 2D holographic photonic quasicrystal are approximately similar with the developed analytical model based on cavity coupling effect. Moreover, the lasing patterns of the 2D CQDs photonic quasicrystal laser exhibit a symmetrical polarization effect by rotating the axis of polarization with a difference of 1200 angle in a round trip. We expect that our findings will provide a new approach to customize the 2D CQDs holographic photonic quasicrystal lasers in the field of optoelectronic devices and miniature lasing systems.

A silicon-based quantum dot random laser.

Herein, a quantum dot random laser was achieved using a silicon nanowire array. The silicon nanowire array was grown by a metal-assisted chemical etching method. A colloidal quantum dot solution was spin-coated on silicon nanowires to form the random laser. The performance of the random laser was controlled by the resistivity of silicon wafers and the length of silicon nanowires. A transition from incoherent random lasing to coherent random lasing was obtained by increasing the resistivity of the silicon wafers. The random lasing threshold increased with an increase in the length of the silicon nanowires. These results may be useful to explore high-performance silicon-based random lasers.