Progress in Quantum Electronics最新文献

Edge-emitting mode-locked quantum-dot (QD) lasers are compact, highly efficient sources for the generation of picosecond and femtosecond pulses and/or broad frequency combs. They provide direct electrical control and footprints down to few millimeters. Their broad gain bandwidths (up to 50 nm for ground to ground state transitions as discussed below, with potential for increase to more than >200 nm by overlapping ground and excited state band transitions) allow for wavelength-tuning and generation of pico- and femtosecond laser pulses over a broad wavelength range. In the last two decades, mode-locked QD laser have become promising tools for low-power applications in ultrafast photonics. In this article, we review the development and the state-of-the-art of edge-emitting mode-locked QD lasers. We start with a brief introduction on QD active media and their uses in lasers, amplifiers, and saturable absorbers. We further discuss the basic principles of mode-locking in QD lasers, including theory of nonlinear phenomena in QD waveguides, ultrafast carrier dynamics, and mode-locking methods. Different types of mode-locked QD laser systems, such as monolithic one- and two-section devices, external-cavity setups, two-wavelength operation, and master-oscillator power-amplifier systems, are discussed and compared. After presenting the recent trends and results in the field of mode-locked QD lasers, we briefly discuss the application areas.

Brillouin dynamic gratings (BDGs) in optical fibers have been developed for more than a decade and gained considerable interests in different photonics fields. Based on its features of flexibility and all-optical generation, BDG has been explored for many applications including distributed optical fiber sensing (temperature, strain, transverse pressure, hydrostatic pressure, and salinity), all-optical signal processing, all-optical delay, microwave photonic filter, and ultrahigh resolution optical spectrometry. Especially in recent years, besides the longitudinal BDG in the backward stimulated Brillouin scattering (SBS), the transverse BDG associated with the forward SBS has been proposed for substance identification and characterization of optical fiber diameter. In this paper, a systematically theoretical analysis of BDG in optical fibers is given and its recent advances in applications is summarized.

In recent years, Gallium Nitride (GaN) has been established as a material of choice for high power switching, high power RF and lighting applications. In c-direction, depending on the surface termination III-nitrides have either a group III element (Al, In, Ga) polarity or a N-polarity. Currently, commercially available GaN-based electronic and optoelectronic devices are fabricated predominantly on Ga-polar GaN. However, N-polar nitride heterostructures due its intrinsic material properties, including opposite polarization field and more chemically reactive surface, can provide benefits for these applications. In this article, some of important electronic and optical properties of N-polar (In, Ga, Al)N thin films and heterostructures have been reviewed. Different techniques that have been used for the epitaxial growth of these materials including tri-halide vapor phase epitaxy (THVPE), metalorganic chemical vapor deposition (MOCVD), and plasma-assisted molecular beam epitaxy (PAMBE) have been discussed. Finally, some of important process technologies that have been developed for fabrication of N-polar GaN high electron mobility transistors are presented.

To manipulate the electrical and optical properties of ultrathin two-dimensional (2D) layered materials, many approaches including the engineering of strain, doping, defects, and chemical absorption have been developed in recent years. However, the researches on crested substrates, which cause strains and emerging functionalities from the rigid substrate are limited. It shows great potential in improving carrier mobility, promoting charge transfer and charge injection, and decreasing the contact resistance of 2D material devices. Here, recent advances on crested substrates in 2D material-based optoelectronic and photonic devices are reviewed. These developments are classified in three aspects: the generation of crested structure in 2D materials; the strain-induced effect and more effects (plasmonic resonance, charge transfer, hot electron injection, optical effect) due to the crested surface; the state-of-the-art of the performance enhancement in 2D materials optoelectronics and photonics. We also present our perspectives on the physics and potential applications based on the crested structures.

The outstanding properties of wide and flexibly tunable emission range, high color saturation, and cost-effectiveness make quantum dots (QDs) promising candidates in display field. However, the vast majority of QDs used in high-performance display devices contain toxic elements such as cadmium (Cd) or lead (Pb). In recent years, with increasing attention to physical health and ecological environment, the application of eco-friendly QDs in light-emitting diodes (LEDs) has been vigorously explored through tremendous efforts in material engineering and device architecture. The external quantum efficiency (EQE) of red InP-based and blue ZnSe-based quantum dot light-emitting diode (QLED) has exceeded 21.4% and 20.2%, which owns good stability and high color purity. In this review, the recent research progress of three major projects implemented on four types of eco-friendly QDs, including existing challenges and possible solutions, and their feedback on device performance are summarized, aiming to provide guidance for the further development of eco-friendly QLEDs.

Recently, thanks to their unique and attractive properties, such as tunable bandgap, high absorption coefficient, and long charge carrier diffusion length, metal halide perovskites have been recognized as one of the emerging candidates for next-generation optoelectronic devices. Optoelectronic devices based on perovskites have achieved significant breakthroughs in a relatively short period of time. However, their commercialization still faces various challenges, including stability, scalability, and reproducibility. Defects are often the culprits behind these problems, either inside the perovskites or at the device interfaces. Therefore, rational utilization of defect engineering to minimize the effect of defects on device performance and control of carrier behavior is the key to achieve efficient and stable perovskite-based optoelectronic devices (PODs). Given the important contribution to the rapid development of PODs, there is an urgent need to systematically investigate and summarize recent research advances in defect engineering. Therefore, in this review, defect physics in PODs are described in detail, the role and importance of defects in various PODs are highlighted, and various strategies for optimizing PODs are reviewed. Finally, based on the latest progresses and breakthroughs, the challenges facing in the future development of metal halide perovskites and their potential significance in the field of the optoelectronic are prospected.

The magneto-optical effect (Faraday effect) was discovered in the middle of the 19^th century. In the latter half of the 20^th century, the practical use of isolators using single crystals (Faraday rotators) using the melt growth method began. One century after Faraday's discovery of the magneto-optic effect, R.L. Coble proved translucency of polycrystalline ceramics. Ceramics may have many scattering sources due to their polycrystalline microstructure, and even from the viewpoint of scattering theory, it was considered impossible to apply them to the generation of coherent light (laser). However, 40 years later, A. Ikesue demonstrated laser ceramics for the first time with performance comparable to that of optical single crystal counterparts. The possibility of laser application of polycrystalline ceramics also makes it possible to apply it to Faraday rotators (optical isolators) that utilize coherence light. A magneto-optical single crystal composed of a single crystal orientation was considered to be superior in that it provided excellent optical performance and an accurate Faraday rotation angle. However, polycrystalline ceramics composed of random crystal orientations can not only provide accurate Faraday rotation angle but can also have a higher extinction ratio than single crystal isolators. A ceramic medium with extremely low scattering and extremely low insertion loss, which cannot be achieved with a single crystal material, has been developed. In addition, new materials, which have Verdet constants several times higher than those of main commercial crystal for isolator, have made it possible to reduce the size of isolator devices. However, these materials cannot be synthesized by the conventional melt-growth method. In the 21^st century, polycrystalline ceramics are paradigms for Faraday rotating elements, and are about to enter a period of change from single crystals to polycrystalline ceramics.

Optical frequency comb, with precisely controlled spectral lines spanning a broad range, has been the key enabling technology for many scientific breakthroughs. In addition to the traditional implementation based on mode-locked lasers, photonic frequency microcombs based on dissipative Kerr and quadratic cavity solitons in high-Q microresonators have become invaluable in applications requiring compact footprint, low cost, good energy efficiency, large comb spacing, and access to nonconventional spectral regions. In this review, we comprehensively examine the recent progress of photonic frequency microcombs and discuss how various phenomena can be utilized to enhance the microcomb performances that benefit a plethora of applications including optical atomic clockwork, optical frequency synthesizer, precision spectroscopy, astrospectrograph calibration, biomedical imaging, optical communications, coherent ranging, and quantum information science.

The epitaxial growth of semiconductor materials in nanowire geometries is enabling a new class of compact, micron scale optoelectronic devices. The deterministic selection and integration of single nanowire devices, from large growth populations, is required with high spatial accuracy and yield to enable their integration with on-chip systems. In this review we highlight the main methods by which single nanowires can be transferred from their growth substrate to a target chip. We present a range of chip-scale devices enabled by single NW transfer, including optical sources, receivers and waveguide networks. We discuss the scalability of common integration methods and their compatibility with standard lithographic methods and electronic contacting.