Multiple-layer InAs/GaAs quantum dot (QD) laser structures were etched to remove the p-side AlGaAs cladding layers to investigate the temperature-dependent photoluminescence (PL) characteristics. Four QD samples, including undoped as grown QDs, p-doped as grown QDs, undoped annealed QDs, and p-doped annealed QDs, were prepared by molecular beam epitaxy (MBE) and a postgrowth annealing process for comparison. Among them, modulation p-doped QD samples exhibit much less temperaturedependent characteristics of PL spectra and notable insensitivity to intermixing compared to undoped ones. This is attributed to the effects of modulation p-doping, which can inhibit holes' thermal broadening in their closely spaced energy levels and significantly suppress In/Ga interdiffusion between QDs and their surrounding matrix. These results provide greater freedom in the choice of MBE growth for high-quality active regions and claddings of QD laser diodes. The superior features of the modulation p-doped QD materials have been transferred naturally to the laser devices. The continuous-wave ground-state (GS) lasing has been realized in both p-doped QD Fabry−Perot (F−P) and laterally coupled distributed-feedback (LC-DFB) narrow ridge lasers with very short cavity length without facet coatings, in which a 1315 nm GS lasing has been found in a F−P laser with a 400 μm cavity length, while single longitudinal mode lasing with a very large tunable range of 140 nm and side mode suppression ratio of 51 dB is achieved in an LC-DFB laser. This work demonstrates great development potential of InAs/GaAs QD lasers for applications in high-speed fiber-optic communication.

Semiconductor broadband light emitters have emerged as ideal and vital light sources for a range of biomedical sensing/imaging applications, especially for optical coherence tomography systems. Although near-infrared broadband light emitters have found increasingly wide utilization in these imaging applications, the requirement to simultaneously achieve both a high spectral bandwidth and output power is still challenging for such devices. Owing to the relatively weak amplified spontaneous emission, as a consequence of the very short non-radiative carrier lifetime of the inter-subband transitions in quantum cascade structures, it is even more challenging to obtain desirable mid-infrared broadband light emitters. There have been great efforts in the past 20 years to pursue high-efficiency broadband optical gain and very low reflectivity in waveguide structures, which are two key factors determining the performance of broadband light emitters. Here we describe the realization of a high continuous wave light power of >20 mW and broadband width of >130 nm with near-infrared broadband light emitters and the first mid-infrared broadband light emitters operating under continuous wave mode at room temperature by employing a modulation p-doped InGaAs/GaAs quantum dot active region with a ‘J’-shape ridge waveguide structure and a quantum cascade active region with a dual-end analogous monolithic integrated tapered waveguide structure, respectively. This work is of great importance to improve the performance of existing near-infrared optical coherence tomography systems and describes a major advance toward reliable and cost-effective mid-infrared imaging and sensing systems, which do not presently exist due to the lack of appropriate low-coherence mid-infrared semiconductor broadband light sources.

A novel reddish-orange phosphor, Ca3Y(2-2x)(Si3O9)2:2xDy(3+), was synthesized via conventional solid-state reaction. Its photoluminescence properties were investigated. With increasing Dy(3+) concentration, the luminescence intensity first increases, reaches the greatest, and then decreases. The concentration quenching mechanism is based on the electric dipole-dipole interaction. The decay times were also determined.