Room-Temperature Planar Lasers Based on Water-Dripping Microplates of Colloidal Quantum Dots

The solution-processable colloidal quantum dots (CQDs) attract great interests in small-size laser applications because of the high quantum yields and the tunable emission wavelengths. The small CQD lasers based on the microplates are of importance in the highly integrated photonic circuits, and the simple and low-cost manufacturing methods to obtain the CQD microplates are greatly desired and appealing in applications. Here, by employing the simple drop-casting and water-dripping method, the high-quality CQD microplates with various shapes and sizes are experimentally manufactured under the proper solvents and solvent ratio as well as environment temperature. Evidently, this manufacturing method does not require any expensive or special instruments. Because of both the large gain coefficients and the high quality factors of the CQD microplates, the room-temperature planar multi- and single-mode CQD lasers with p-polarized emissions are experimentally realized under low pump thresholds. Moreover, it is demonstrated that the planar CQD microplate laser is easy to be integrated with the waveguides on chips. This simple and low-cost method to manufacture the CQD microplates opens a wide range of possible activities in the area of solid-state small lasers, which are important building blocks for the true integration of optoelectronic circuitry

Temperature Dependence of the Energy Band Diagram of AlGaN/GaN Heterostructure

Temperature dependence of the energy band diagram of AlGaN/GaN heterostructure was investigated by theoretical calculation and experiment. Through solving Schrodinger and Poisson equations self-consistently by using the Silvaco Atlas software, the energy band diagram with varying temperature was calculated. The results indicate that the conduction band offset of AlGaN/GaN heterostructure decreases with increasing temperature in the range of 7 K to 200 K, which means that the depth of quantum well at AlGaN/GaN interface becomes shallower and the confinement of that on two-dimensional electron gas reduces. The theoretical calculation results are verified by the investigation of temperature dependent photoluminescence of AlGaN/GaN heterostructure. This work provides important theoretical and experimental basis for the performance degradation of AlGaN/GaN HEMT with increasing temperature

Roadmap on structured waves

International audienceStructured waves are ubiquitous for all areas of wave physics, both classical and quantum, where the wavefields are inhomogeneous and cannot be approximated by a single plane wave. Even the interference of two plane waves, or of a single inhomogeneous (evanescent) wave, provides a number of nontrivial phenomena and additional functionalities as compared to a single plane wave. Complex wavefields with inhomogeneities in the amplitude, phase, and polarization, including topological––––– structures and singularities, underpin modern nanooptics and photonics, yet they are equally important, e.g. for quantum matter waves, acoustics, water waves, etc. Structured waves are crucial in optical and electron microscopy, wave propagation and scattering, imaging, communications, quantum optics, topological and non-Hermitian wave systems, quantum condensed-matter systems, optomechanics, plasmonics and metamaterials, optical and acoustic manipulation, and so forth. This Roadmap is written collectively by prominent researchers and aims to survey the role of structured waves in various areas of wave physics. Providing background, current research, and anticipating future developments, it will be of interest to a wide cross-disciplinary audience