A Colloidal-Quantum-Dot Integrated U-Shape Micro-Light-Emitting-Diode and Its Photonic Characteristics.

A special micro LED whose light emitting area is laid out in a U-like shape is fabricated and integrated with colloidal quantum dots (CQDs). An inkjet-type machine directly dispenses the CQD layer to the central courtyard-like area of this U-shape micro LED. The blue photons emitted by the U-shape mesa with InGaN/GaN quantum wells can excite the CQDs at the central courtyard area and be converted into green or red ones. The U-shape micro LEDs are coated with Al2O3 by an atomic layer deposition system and exhibit moderate external quantum efficiency (6.51% max.) and high surface recombination because of their long peripheries. Low-temperature measurement also confirms the recovery of the external quantum efficiency due to lower non-radiative recombination from the exposed surfaces. The color conversion efficiency brought by the CQD layer can be as high as 33.90%. A further continuous CQD aging test, which was evaluated by the strength of the CQD emission, under current densities of 100 A/cm2 and 200 A/cm2 injected into the micro LED, showed a lifetime extension of the unprotected CQD emission up to 1321 min in the U-shape device compared to a 39 min lifetime in the traditional case, where the same CQD layer was placed on the top surface of a squared LED.

Improved Long-Term Reliability of a Silica-Encapsulated Perovskite Quantum-Dot Light-Emitting Device with an Optically Pumped Remote Film Package.

In this study, inorganic perovskite (CsPbBr3) quantum dots are wrapped in SiO2 to provide better performance against external erosion. Long-term storage (250 days) is demonstrated with very little changes in the illumination capability of these quantum dots. While in the continuous aging procedure, different package architectures can achieve very different lifetimes. As long as 6000 h of lifetime can be expected from these quantum dots, but the blue shift of emission wavelength still needs more investigation.

Widely Tunable Single/Dual RF Signal Generation by a Monolithic Three-Section DFB Laser.

A three-section distributed feedback laser with a 2.5 InP/air pair of distributed Bragg reflectors (DBRs) was fabricated and analyzed in terms of its microwave generation capability. A widely tunable single radio frequency (RF) signal can be detected using optical heterodyning, and the tuning range is from 2 to 45 GHz. The incorporation of the third section provides an opportunity to present the dual RF operation when three emission peaks are near to each other in the wavelength domain. The proposed design provides a 21.3% enhancement in the RF tuning range compared with the range of a two-section laser (35.29 GHz versus 42.81 GHz). The compactness of the proposed device can be useful for future radio-over-fiber applications.