Progress in Quantum Electronics最新文献

The terahertz (THz) quantum cascade laser (QCL), first demonstrated in 2002, is among the most promising radiation sources in the THz region owing to its high output power and broad frequency coverage from ∼1.3 to ∼5.4 ​THz and sub-terahertz, without and with assistance of external strong magnetic field. The operation of THz QCLs, however, has thus far been limited to applications below room temperature. Recent advances in THz QCL research have principally focused on optimization of quantum design, fabrication, and growth techniques to improve the maximum operating temperature of THz QCLs; these efforts culminated in a recent demonstration of pulse-mode lasing at temperature up to 250 ​K. Research interests continue to be propelled as new maximum lasing temperature record are set, heating up the race to realize room-temperature operation of THz QCLs. This paper critically reviews key achievements and milestones of quantum designs, fabrication techniques, and simulation methods applicable to the high temperature operation of THz QCLs. In addition, this paper provides a succinct summary of efforts in this field to pinpoint the remaining challenges and provide a comprehensive picture for future trends in THz QCL research.

Photonic spin and orbital angular momenta, which are determined by the polarization and spatial degrees of freedom of photons, are strongly coupled with each other in subwavelength structured metasurfaces. The photonic spin-orbit interaction (PSOI) results in the splitting of the degenerated system states. In this review, we focus on the principles of symmetric PSOI associated with the conjugated geometric phase modulation as well as the asymmetric PSOI resulting from the additional localized phase manipulation. Recent advances and important applications of symmetric and asymmetric PSOI in metasurfaces are also discussed. We finally highlight with our perspective on the remaining challenges and future trends in this field.

Random Lasers (RLs) and Random Fiber Lasers (RFLs) have been the subject of intense research since their first experimental demonstration in 1994 and 2007, respectively. These low coherence light sources rely on multiple scattering of light to provide optical feedback in a medium combining a properly excited gain material and a scattering disordered structure. It is the feedback mechanism which makes RLs/RFLs quite different from conventional lasers, with the later relying on an optical cavity usually formed by two static mirrors. This characteristic makes the RLs and RFLs devices to become cavityless, although not modeless, and present features of complex systems, whose statistics of intensity fluctuations are quite relevant. In addition, RLs can be designed in three-dimensional (3D) geometry, typically powders or colloids, in two-dimensional (2D) geometries, such as planar waveguides or thin-films, and one-dimensional (1D or quasi-1D) geometry, generally in optical fibers, known as the RFLs. The advantage of 1D geometry is the inherent directionality of the RFL emission, which otherwise is multidirectional in 3D geometry. In this review paper, we initially describe the basic theoretical framework supporting laser emission due to feedback in disordered structures. We then provide an updated vision of the types of RLs and RFLs that have been demonstrated and reported, from dyes solutions embedded with nano/submicron-scatterers composites to rare-earth doped micro or nanocrystals and random fiber Bragg gratings as the scattering structure. The influence of optical processes due to second-, third- and high-order nonlinearities on the intensity behavior of RLs are discussed. Subsequently, we review multidisciplinary studies that lead to the classification of RLs as complex systems exhibiting turbulence-like characteristics, photonic phase-transitions presenting replica symmetry breaking and intensity fluctuations satisfying Lévy-like statistics, and the so-called Floquet phase. Furthermore, we also highlight technological applications that includes sensing, optical amplification, and biomedical imaging. The review concludes pointing out potential directions in basic and applied research in the field of RL and RFL.

Mid-infrared region (2–20 ​μm) is an important region of electromagnetic spectrum. Most of the molecules including CH₄, CO, NO, NO₂, C₆H₆, TNT, NH₃, SF₆, HNO₃, greenhouse gas radiation etc. have their fundamental vibrations in this domain. Thus, the mid-infrared region is known as ‘molecular fingerprint region’ and desirable to get the signature of these molecules. Tellurite and chalcogenide glasses have the advantages of a wide transparency window (up to ~20 ​μm) and very high optical nonlinearities, making them decent candidates for the mid-infrared supercontinuum generation. Photonic crystal fibers provide the wavelength-scale periodic arrangement of microstructure along their length. The core of the photonic crystal fibers and two-dimensional photonic crystal based on diverse geometries and the materials, permitting supercontinuum generation due to various nonlinear effects in an enormously broad spectral range. In this review paper, we report the recent developments in the field of mid-infrared supercontinuum generation in both the tellurite and chalcogenide glass state-of-the-art optical fibers. Particular attention is paid to the mid-infrared supercontinuum generation in the step-index, suspended-core, tapered, and photonic crystal fibers or microstructured optical fibers in tellurite and chalcogenide glasses. The coherence property of mid-infrared supercontinuum generation in all-normal dispersion engineered specialty optical fibers is also reviewed.

Since the seminal work by J. H. Poynting, light has been known to carry momentum and angular momentum. The typical dynamical features of light and its interactions—termed spin–orbit interactions (SOIs), which have been investigated intensely over the last 30 years—play a crucial role in various light-matter interactions, for example: spin Hall effect, spin–orbit conversion, helicity-controlled unidirectional excitation of light, and their inverse effects, which leads to plenty of applications including optical manipulation, communications, imaging, sensing, nanometrology, on-chip optoelectronic technologies and interdisciplinary researches. In particular, the SOI of light in isotropic inhomogeneous media is a fine, subwavelength effect accomplished through the intrinsic coupling between light's phase, polarization and position. Therefore, the traditional methods of near-field measurements, such as near field scanning optical microscopy (NSOM), have been widely employed to reveal the optical SOIs intuitively by measuring the intensity of light. Very recently, with modern advanced nanofabrication techniques, many measurement techniques based on nanoparticles, nanoantennas, and nanoprobes of special designs have been proposed to understand the optical SOIs visually by characterizing the polarization and spin/orbital features of light. This endeavor has led to the development of chiral quantum optics, spin optics, and topological photonics, and resulted in novel applications requiring optical manipulations and angular momentum communications, chiral imaging, nanometrology, and robust spin-based devices and techniques for quantum technologies. Here, we review the near-field techniques for measurements of optical SOIs together with their potential applications. We start with a theoretical overview of momentum and angular momentum properties of generic optical fields and typical phenomena involving optical SOIs. Then, we overview the theoretical basis and latest achievements of the near-field measurement techniques, including NSOM, optical manipulations, nanoantenna, and nanoprobes of special designs, all relevant to optical SOIs. A comprehensive classification is then constructed of all known methods of optical near-field measurements for the SOI of light and novel techniques identified for future applications.

Biosensor technology is a quite attractive and rapidly developing research field in recent years, and the sub field of optical photonic crystal (PC) biosensor based on label free sensing technology has also made great progress in this period. This review mainly concentrates on advances in the label free refractometric sensing based two dimensional (2D) PC slab biosensors particularly in the last decade, emphasizing the development and evolution of structural design. It begins with a brief discussion on the basic principles and design methods of label free 2D PC biosensors. Then, the sensors are classified according to the designed geometric structure and research progress of various sensors is reviewed, highlighting efforts dedicated to improving the transducer configuration and integration. Additionally, surface functionalization methods for different materials to produce reproducible surface properties and different detection methods for biological targets are introduced for evaluation. 2D PC refractometric biosensors have been applied to a great many applications varying from biotechnology, food safety, water quality monitoring to clinical diagnosis. Finally, the authors’ views on current limitations of the slab for biosensing as well as the optimizable aspects are presented.

III-nitride semiconductor laser directly grown on Si is a potential on-chip light source for Si photonics. Moreover, it may greatly lower the manufacture cost of laser diodes and further expand their applications. Therefore, III-nitride lasers grown on Si have been pursued for about two decades. Different from GaN homoepitaxy on free-standing GaN substrates, III-nitride semiconductors grown on Si substrates are usually rich with strain and threading dislocations due to the large mismatch in both lattice constant and coefficient of thermal expansion between GaN and Si substrates, which hindered the realization of electrically injected lasing. The key challenges in the direct growth of high-quality III-nitride semiconductor laser materials on Si substrates, as well as their corresponding solutions, are discussed in detail. Afterwards, a comprehensive review is presented on the recent progress of III-nitride semiconductor lasers grown on Si, including Fabry-Pérot cavity lasers, microdisk lasers, and the lasers with nanostructures, as well as the monolithic integration of lasers on Si. Finally, the further development of III-nitride semiconductor lasers grown on Si is also discussed, including the material quality improvement and novel device structures for enhancing optical confinement and reducing electrical resistance, with a great prospect for better performance and reliability.

Integration of embedded dielectric structures with crystalline III-V materials has generated significant interest, due to a host of important applications and material improvements that are central to high performance optoelectronic devices. The core challenge is the production of high-quality crystalline layers grown above embedded dielectric materials, requiring the growth processes of both lateral epitaxial overgrowth (LEO) and coalescence. In this review article, we provide a detailed and up-to-date description of the recent advances in both LEO and coalescence in III-V materials, from its extension to molecular beam epitaxial growth and high-quality coalescence in InP and GaAs to emerging applications that utilize encapsulated air voids to enhance optical devices. We also explore the epitaxial integration of other materials, particularly metals, with III-V semiconductors.

Improving the energy efficiency of electronics is one of the grand challenges of semiconductor device physics, as global energy consumption by electronics grows in tandem with society’s growing reliance on information technology. Computationally intensive applications such as artificial intelligence further incentivizes the improvement of energy efficiency of electronics. At the corpuscular level of the transistor, the challenge is to reduce the operating voltage of the electronic switch while maintaining a sufficient on/off current ratio for reliable circuit operation. Monolayer graphene is a light material with low elastic modulus for flexure and low adhesion energy, ideal for the development of electromechanical switches with low-voltage operation. Critically, monolayer graphene has an elastic modulus lower than that of any other membrane due to its atomic thinness, which in turn enables deflection with less force than any other membrane. In this article, we review recent progress in the development of low-voltage graphene electromechanical switches. We present a general overview of the motivation for low-voltage switches, thermodynamic limits, and the scaling of on/off current ratio with voltage. A summary of the theory of suspended graphene monolayer switches follows. Simple theoretical models for the scaling of pull-in voltage, actuation energy and adhesion energy with device dimensions are reviewed. Experimental work over the past decade towards the realization of suspended graphene switches in both two-terminal and three-terminal configurations is summarized. Our review concludes with an outlook on the continued development of low-voltage graphene switches.

The paper is a review of gas lasers pumped by runaway electrons preionized diffuse discharge (REP DD). The various conditions under which the discharge occurs are described. It is shown that in the presence of the highly non-uniform electric field strength distribution in a gap filled with dense gases, a stable diffuse discharge is ignited without the use of additional sources of ionizing radiation. This, in turn, is achieved by using discharge gaps, in which at least one of the electrodes has a small radius of curvature (e.g., “point-plane”, “blade-blade” and so on), and high-voltage (10s–100s ​kV) pulses with a (sub)nanosecond rise time. With this method of forming the discharge the runaway electrons can produce X-ray quanta in the gap and, together with them, provide preionization of the laser gas mixture. The dense nonequilibrium low-temperature plasma of this discharge can remain diffuse during the entire excitation time, including single pulse excitation and repetitive mode at the voltage pulse repetition rate up to several kHz. The properties and parameters of REP DD plasma are considered. Experimental and simulated characteristics of stimulated emission of REP DD plasma in various gaseous media are presented.