Advanced Photonics Research最新文献

SiGe-SiO₂-based structures present high interest for their high photosensitivity from visible to short-wavelength infrared. Herein, two postdeposition annealing procedures, that is, rapid thermal annealing (RTA) and rapid-like furnace annealing (FA), are compared. Both RTA and FA are performed at 600 °C for 1 min for SiGe nanocrystals (NCs) formation in SiO₂ matrix in Si/SiO₂/SiGe/SiO₂ structures deposited by magnetron sputtering. The FA imitates RTA resulting in enhanced spectral response. X-ray diffraction, transmission electron microscopy, and Raman spectroscopy are carried out showing Ge-rich SiGe NCs with 11.3 ± 1.2 nm size for RTA and 9.4 ± 0.8 nm for FA. Photocurrent spectra for both structures show several peaks that are annealing dependent. The photocurrent intensity for FA samples is ≈7 times higher than RTA samples while cutoff wavelengths are slightly different, that is, 1365 nm for FA and 1375 nm for RTA. The FA structures show (at −1.5 V) over 4 A W⁻¹ responsivity at 730 nm, 6.4 × 10⁷ Jones detectivity at 735 nm, and 2.2 × 10⁷ Jones at about 1210 nm. FA structures contain small SiGe NCs with incorporated residual strain, while RTA ones are formed of columnar SiGe NCs separated by SiGeO_x amorphous regions and show increased tensile strain in the SiGe.

Tuning the color of Au has been a longstanding problem in the luxury industry. Conventional approaches, involving Au alloying, compromise purity and demand distinct alloy compositions for each hue. This study demonstrates a lithography-free method for generating structural colors on a gold surface by adjusting the thickness of titanium dioxide, a high-index dielectric. While color tuneability is limited if TiO₂ is coated directly on the Au surface, a range of vivid colors can be generated if a 50−100 nm thick AuAl₂ underlayer is used. AuAl₂, an accepted alloy for purple gold, broadens the color gamut, providing a protective coating without diminishing gold purity. The reflectance dip of the bilayer structure exhibits a significant red shift with increasing thickness of the TiO₂ layer, allowing diverse colors by TiO₂ insulator tuning. Simulation studies corroborate experimental results, affirming that coating a TiO₂ layer on the AuAl₂ underlayer yields a wide range of colors. This method, based on thin-film interference, shows promise for widespread use, offering a broad spectrum of structural colors in an industry striving for diverse Au color representation.

Recent reports of upconversion and white light emission from graphitic particles warrant an explanation of the physics behind the process. A model is offered, wherein the upconversion is facilitated by photoinduced electronic structure modification allowing for multiphoton processes. As per the prediction of the model, it is experimentally shown that graphite upconverts infrared light centered around 1.31 μm (0.95 eV) to broadband white light centered around 0.85 μm (1.46 eV). The results suggest that upconversion from shortwave infrared (≈3 μm, 0.45 eV) to visible region may be possible. The experiments show that the population dynamics of the electronic states involved in this upconversion process occur in the timescale of milliseconds.

Diffractive Neural Networks

In article number 2300310, Ying Zhi Cheong, Blanca del Rosal, Sharath Sriram, and co-workers propose and demonstrate a microscale multi-layer diffractive neural network approach that classifies various wavelengths in the visible spectrum. This miniaturised classification approach, achieved through two-photon polymerization, has potential application in medical diagnosis to material science, enabling rapid detection of analytes based on the presence of optical extinction bands at specific wavelengths.

Viologens, with their unique redox-active properties, have garnered increasing attention in the development of electrochromic devices. This review focuses on key strategies in molecular design, synthesis methodologies, and tailored functionalities that have propelled the field forward from 2019 to the present. The convergence of these approaches has led to the construction of viologen-based electrochromic materials with enhanced performance, stability, and responsiveness. The review not only examines the current state of the field but also explores promising outlooks and opportunities, including tailored applications, environmental sustainability, and integration with emerging technologies. The synergy between molecular engineering and viologen-based electrochromic materials holds significant promise, shaping the future of dynamic, responsive materials in diverse technological domains. This review serves as a valuable resource for researchers, offering insights into recent breakthroughs and inspiring further advancements in this rapidly evolving field.

Perovskites exhibit appealing optical and electrical properties, making them attractive candidates for efficient luminescent materials with low-cost and straightforward fabrication processes. Their versatility is highlighted by the ability to deposit perovskite thin films on various substrates, including silicon, glass, sapphire, and flexible substrates, enabling potential monolithic integration on silicon for applications such as photonic integrated circuits, high-speed communication. Extensive studies on perovskite light-emitting diodes have shown external quantum efficiencies exceeding 20% across a wide spectral range from deep blue to near-infrared, with chirality. Additionally, perovskite-based lasing action has been achieved under pulsed optical excitation and continuous-wave operation, as well as in functional diode structures. However, realizing electrically driven perovskite laser diodes for practical applications requires the injection of intense current densities. This review provides a comprehensive overview of the historical progress in perovskite lasers and light-emitting didoes, along with important design considerations essential for their development.

Herein, lutecium silicate is used as a rock example to investigate its two high-pressure phases (7.4 GPa: HP-II and 25.3 GPa: HP-III) and lattice dynamics by in situ high-pressure Raman scattering up to 35.1 GPa. The evidence for a highly symmetrical insulator HP-III phase is obtained. Importantly, the high-pressure structure (metastable phases) after pressure quenching is also intercepted, indicating pressure-induced permanent densification. These findings provide Raman evidence for pressure-induced successive phase transitions of highly symmetric insulators intercepted in prototype Lu₂SiO₅ and physical insights to explain the self-regulation of rare earth-rich regions in facilitating highly effective global carbon cycling.

The high-temperature layered superconductor (HTS) BSCCO is one of the key quantum material platforms in THz science and technology. Compact, stable, and reliable BSCCO THz photonic integrated circuit components can be developed to effectively and efficiently control and manipulate THz wave radiation, especially for future communication systems and network applications. Herein, the design, simulation, and modeling of ultrafast THz metamaterial photonic integrated circuits are reported on a few nanometer-thick HTS BSCCO van der Waals (vdWs), capable of the active modulation of phase with constant transmission coefficient over a narrow-frequency range. Meanwhile, the metamaterial circuit works as an amplitude modulator without significantly changing the phase in a different frequency band. Under the application of ultrashort optical pulses, the transient modulation dynamics of the THz metamaterial offer a fast-switching timescale of 50 ps. The dynamics of picosecond light–matter interaction, Cooper pairs breaking, photoinduced quasiparticles generation and recombination, phonon bottleneck effect, and emission and relaxation of bosons in BSCCO vdW metamaterial arrays are discussed for the potential application of multifunctional superconducting photonic integrated circuits in communication and quantum technologies.

Although orbital angular momentum (OAM) is extensively explored and researched in various scientific domains, its practical application in wireless communications still faces numerous challenges. Notably, existing OAM beam generation technologies need to meet the diversified demands of modern wireless communication, such as miniaturization, cost-effectiveness, and system integration. Driven by the immense potential of OAM in communication systems, in this work, an innovative method based on leaky cables capable of simultaneously generating multiple vortex beams, overcoming a series of implementation issues associated with multiplexing emitters, is introduced. A design prototype is fabricated and tested, and the measurement results align closely with the simulations, validating the multifunctionality and practicality of the method. Moreover, the proposed strategy can seamlessly extend to optical frequencies using the concept of leaky fibers. In this method, not only efficient spatial utilization and excellent isolation are realized but also high cost-effectiveness is possessed. Compared to previous strategies, this technique may have an impact on simplifying the establishment of communication system platforms based on OAM multiplexing.

Coupled microring lattices are versatile photonic systems that can be used to realize various topological phases of matter. In two-dimensional (2D) microring lattices, the periodic and unidirectional circulation of light in each microring gives rise to a time-like dimension, so that the lattice emulates a (2 + 1)D system with much richer topological behaviors than static 2D lattices. Accurate treatment of these systems requires a departure from the static tight-binding model of coupled resonators and take into account the periodic coupling sequence of light in the lattice network. This article provides an overview of the theory and design of (2 + 1)D microring lattices for realizing Floquet topological photonic insulators (TPIs). Particular focus is placed on the microring Lieb lattice with perfect couplings, which emulates an anomalous Floquet insulator with all flat bands. Such a system exhibits some unique properties, including wide edge mode continuum exceeding a Floquet–Brillouin zone, super-robustness to lattice disorder, Aharonov–Bohm (AB) caging and compact localized flat-band states that can be used to realize high-quality factor topological resonators. All-bands-flat Floquet–Lieb microring lattices provide a versatile platform for investigating topological physics as well as potential applications in realizing topologically-protected photonic devices.