Lasing from organic quasicrystal fabricated by seven- and nine-beam interference

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.

Construction of photorefractive photonic quasicrystal microstructures by twisted square lattices

A convenient method to fabricate two-dimensional photonic quasicrystal microstructures was experimentally demonstrated by using a rotatable four-wedge prism. Two-dimensional eightfold symmetric quasicrystal microstructures are formed by two groups of twisted square lattices in a photorefractive crystal. The experimental devices of this method are simple and stable without complicated optical adjustment equipment. Optical-induced quasicrystal microstructures are analyzed and verified by magnified imaging and far-field diffraction pattern imaging. The method can be extended to fabricate more complex quasicrystal and moiré lattice microstructures. We numerically demonstrate that this method can be used to fabricate other complex photonic microstructures by using different multi-wedge prisms and adjusting the rotation angle properly.

Coherent Random Lasing in Colloidal Quantum Dot-Doped Polymer-Dispersed Liquid Crystal with Low Threshold and High Stability

High-concentration (2-10 wt %) ZnCdSeS/ZnS alloyed quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared via ultraviolet (UV) curing. The QD-PDLC morphology and resonance characteristics of a coherent random laser were investigated. The doping concentration of the liquid crystal and quantum dots was varied to investigate its effect on the lasing threshold, line width, and stability with respect to the density and grain size of the liquid crystal droplets inside the PDLC structure. Furthermore, the QD-PDLC laser performance was influenced by the pump position and area because of spatial localization of the random resonators. Moreover, the QD-PDLC showed good long-term stability; after 15 days of laser excitation (3 h/day), the laser output was maintained at 92% of the original emission intensity. The random laser threshold was as low as 50 μJ/cm² with the optimized preparation process, which suggested strong potential for applications in polymer random fiber lasers, sensors, and displays.

Low threshold optically pumped lasing from MEH-PPV quasi-periodic photonic crystal microcavity

An optically pumped two-dimensional organic quasi-crystal microcavity laser is demonstrated based on conjugated polymer poly(2-methoxy, 5-(2^'-3ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV). The optical resonator consists of the octagonal quasi-crystal for light localization in-plane by the bandgap effect and the distributed Bragg reflector introduced between the slab-substrate interface by inhibiting the scattering and absorption of light in the substrate to achieve vertical confinement of the light. A modified point-defect traps and localizes photons into the microcavity, forcing the wave oscillation along the vertical waveguide. The experimental results show that the single-mode lasing action by optical pumping is observed at 602.2 nm with an FWHM of 0.7 nm. The threshold of lasing is lowered to 6.9 μJ/pulse.

Low-threshold, single-mode, and linearly polarized lasing from all organic quasicrystal microcavity

Organic microcavity lasers based on liquid crystals have attracted substantial attention due to their easy processing, compact volume and excellent tunable properties. However, the threshold of traditional holographic polymer dispersed liquid crystals (H-PDLCs) laser doped with dye is usually as high as several tens of μJ/pulse, which hinders its broad applications. Herein, we demonstrate a low-threshold lasing from quasicrystal based on H-PDLCs. An conjugated polymer poly (2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylenevinylene (MEH-PPV) film is coated on the inner surface of glass substrate to dramatically reduce the lasing threshold, which is 20 times lower than that of dye-doped microcavity laser. A low threshold, single-mode, linearly polarized lasing is achieved when the thickness of MEH-PPV film is optimized at 80 nm. Due to its easy fabrication, excellent performance and bio-compatibility, this compact coherent light source may be useful in lab-on-chip applications such as detection, sensing and analyzing, as well as display, optical communications, and other photonic fields.