Advanced Photonics Research最新文献

Metalens THz Emitter

In article number 2400125, Hyunseung Jung, Oleg Mitrofanov, and co-workers present a metalens for achieving focused terahertz (THz) beam generation using InAs nanoscale resonators. This metalens enables binary-phase THz pulse generation under ultrafast near-IR pump excitation, paving the way for a flexible and compact THz generation platform for applications in imaging, spectroscopy and communications.

The luminescent solar concentrator (LSC) can function as an electricity-generating window whose performance is hindered by an inherent trade-off between power conversion efficiency and visible light transmission. To optimize this trade-off, a numerical algorithm is used to find the power conversion efficiency of 92 luminophores, ensuring an average visible transmission >55% and a color rendering index >70. Furthermore, double- and triple-stacked LSC configurations and single LSCs with two- or three-embedded luminophores are optimized. All tested LSC configurations are found to be limited to a power conversion efficiency of around 1% for window-appropriate transparencies.

Analyzing or probing a complex-structured light field with a simple model to obtain its mode composition sequence and phase delays among eigenmodes is challenging. Currently, there are numerous methods for calculating the weight and analyzing the amplitude of structured light eigenmodes, particularly on orbital angular momentum light field. However, the complete mode spectrum decomposition including the eigenmodes’ indexes with the intensity coefficients and relatively phase delays still needs the comprehensive solution. In this work, the diffractive optical method to extract the complete information of complex-structured light field composed by eigenmodes superimposed state is detailly designed and proved. Through the interference between the inverse conversion of eigenmodes in the Fourier domain, complete mode spectrum can be constructed with eigenmode ordinals, amplitude weight coefficients, and relative phases. To the best of the knowledge, this marks the inaugural use of a simple computational hologram method to fully decompose the mode spectrum information, thereby obtaining more crucial intrinsic information about the intermode phases without additional efforts. This approach on analyzation and description can serve as a vital general tool for analyzing the intensity, phase, and Poynting vector field of complex-structured light fields.

With the rapid development of communication networks and computing, optical switches as an important elementary unit are highly needed. In this article, a silicon-based optical switch with $��{�\text{Ge}�}_2�{�\text{Sb}�}_2�{�\text{Te}�}_5�$ (GST)-enabled phase-shifting region is proposed. This optical switch is based on contra-directional couplers composed of two phase-shifted Bragg gratings. To minimize the impact of GST absorption loss, GST is only used in the phase-shifting area, and the switching function is achieved by changing the state of GST. In the results, it is shown that the proposed device has a 3 dB operation bandwidth of about 163.2 GHz (1.394 nm) and an extinction ratio of about 19.06 dB for the drop port and about 20.25 dB for the through port. The loss at the central operational wavelength is about 1.3 and 1.04 dB for the through port and the drop port, respectively, and the largest loss over the entire operation bandwidth for these two ports is 1.66 and 2.35 dB. Furthermore, the optical switch is shown to be bidirectional, achieving similar performance when light propagates in the opposite direction. Compared with previous works, the proposed optical switch realizes wider operation bandwidth, higher extinction ratio, and lower loss.

The increasing demand for novel mirror coating designs for new generation of gravitational wave detectors is stimulating significant research interest in investigations of reflective properties of metasurfaces. Given this strong interest, this article details a systematic methodology for fabricating reflecting metasurfaces (metamirrors) designed to operate at target wavelengths of 1064 or 1550 nm. The proposed metasurfaces consist of silicon cylindrical nanoparticles placed on a sapphire substrate. First, the dimensional parameters of the structures are thoroughly selected through numerical simulations combined with material characterization. The configurations are subsequently analyzed analytically to reveal the mirror effect, which arises from the excitation of electric and magnetic dipole moments. Following this, the metasurfaces are fabricated and experimentally characterized, demonstrating reflectivity exceeding 95% around the design wavelengths, which is in good agreement with theoretical predictions. Overall, the work demonstrates the feasibility and detailed methodology for the fabrication of thin, lightweight metamirrors capable of achieving near-perfect reflectivity at the specified target wavelengths.

This article develops a Monte Carlo model to optimize a newly introduced tandem luminescent solar concentrator. This innovative structure comprises two parallel transparent polymeric waveguides separated by an air gap. The first waveguide, which is exposed to sunlight, contains fluorophores and performs as a traditional luminescent solar concentrator. In contrast, the second waveguide is equipped with an inner polarization volume grating layer, strategically placed to couple the emitted photons within the escape cone, directing them into the second waveguide and preventing reabsorption. The finite difference time domain method is employed to optimize the performance of this grating. The results show a significant improvement in external photon efficiency compared to the conventional luminescent solar concentrator.

Herein, a holographic optical element (HOE) printing technique which maintains shapes and sizes of hogels across diverse focal positions, and aberration-corrected HOEs which are fabricated by it are proposed. The proposed HOE printer employs nonpixelated focus modulators composed of double 4f optics in reference and signal beam paths to record hogels with the consistent shapes, which is validated via the ray tracing simulation. An optimization algorithm is developed for aberration-corrected HOEs, dedicated to the proposed printing system. Imaging simulations verify the improved image quality compared to a baseline case by showing a 5 times sharper point spread function. As the experimental verification, a HOE printer is realized, which provides 1 × 1 mm of hogels consistently over 20° × 20° of angular ranges and 8 diopters of focal length changes. Displaying experiments using printed HOEs (mono-colored and full-colored ones) verify the proposed method with aberration-corrected and see-through images.

Halide perovskite solar cells (PSCs) have shown remarkable power conversion efficiencies. However, the inherent defect issues of perovskite materials still limit their performance and long-term stability, resulting in lifespans far from commercial standards. With their noninvasive approach to probing the electronic and vibrational properties of materials, spectroscopic techniques have become crucial tools for uncovering and understanding defect states and complex charge carrier dynamics in halide perovskites. This review explores the application of various advanced spectroscopic techniques in PSCs to elucidate the complex behaviors of charge carriers within PSCs. These techniques reveal detailed temporal and spatial distributions of charge carriers, enabling precise analysis of defect impacts and interfacial charge transfer processes. By integrating spectroscopic data, it is possible to more accurately identify and mitigate defect-induced nonradiative recombination and charge transfer, thereby enhancing the stability and efficiency of PSCs. This comprehensive spectroscopic understanding is crucial for developing innovative technologies to accelerate the commercial viability of PSCs.

GaN-Based Blue Laser Diodes

In article number 2400119, Wenyu Kang, Junyong Kang, and co-workers develop an anti-aging technology for high-power GaN LD from mechanism investigation to degradation suppression. This cover depicts a person in different aging stages, indicating the severe degradation issues in high-power LD and the effectiveness of this anti-aging technology.

Spintronic Terahertz Emitters

In article number 2400064, Mathias Vanwolleghem and co-workers experimentally demonstrate a close to 100-fold improvement of the power efficiency of inverse spin Hall emitters by maximizing the impact of the electromagnetic environment of the nanometric emitter. As a result, by moving from a basic emitter on a bare substrate to one functionalized by a resonant crystal cavity and an impedance matched emitting substrate, the emitted THz field pulses can reach several MV/cm peak strengths without any echo behavior.