Advanced Photonics Research最新文献

The pursuit of lead-free alternatives to lead halide perovskites has gained significant momentum due to the environmental concerns associated with lead toxicity. The adverse effects of lead on human health and the environment have prompted a shift toward developing sustainable and eco-friendly perovskite materials for various optoelectronic devices. This shift is particularly vital in emerging technologies where perovskites play a crucial role, such as solar cells, X-ray detectors, photodetectors, light-emitting diodes (LEDs), etc. Consequently, it is paramount to understand the fundamental properties, synthesis methods, and structural characteristics of lead-free perovskites. This review aims to provide a comprehensive analysis of the intricate relationship between the structures and properties of lead-free perovskites, shedding light on their applications across diverse fields. The focus on environmentally benign, high-performing, and lead-free perovskite materials underscores the urgency and significance of research efforts in driving the development of sustainable and efficient optoelectronic technologies.

The direct growth of III-V materials on silicon is a key enabler for developing monolithically integrated lasers, offering substantial potential for ultradense photonic integration in vital communications and computing technologies. However, the III-V/Si lattice and thermal expansion mismatch pose significant hurdles, leading to defects that degrade lasing performance. This study overcomes this challenge, demonstrating InAs/GaAs-on-Si lasers that perform on par with top-tier lasers on native GaAs substrates. This is achieved through a newly developed epitaxial approach comprising a series of rigorously optimized growth strategies. Atomic-resolution scanning tunneling microscopy and spectroscopy experiments reveal exceptional material quality in the active region and elucidate the impact of each growth strategy on defect dynamics. The optimized III-V-on-silicon ridge-waveguide lasers demonstrate a continuous-wave threshold current as low as 6 mA and high-temperature operation reaching 165 °C. At 80 °C, critical for data center applications, they maintain a 12 mA threshold and 35 mW output power. Furthermore, lasers fabricated on both Si and GaAs substrates using identical processes exhibit virtually identical average threshold current. By eliminating the performance limitations associated with the GaAs/Si mismatch, this study paves the way for robust and high-density integration of a broad spectrum of critical III-V photonic technologies into the silicon ecosystem.

Analog computing based on miniaturized surfaces has gained attention for its high-speed and low-power mathematical operations. Building on recent advances, an anisotropic space-time digital metasurface for parallel and programmable wave-based mathematical operations is proposed. Using frequency conversions, our metasurface performs 1st-order and 2nd-order spatial differentiations, integrodifferential equations, and sharp edge detection in spatially encoded images. The anisotropic nature of the meta-particle enables independent and simultaneous operations for two orthogonal polarizations. Reconfigurability is achieved through tunable gate biasing of an indium tin oxide layer. Illustrative examples demonstrate that the metasurface's output signals and transfer functions closely match ideal transfer functions, confirming its versatility and effectiveness. Unlike other wave-based signal processors, the design handles wide spatial frequency bandwidths, even with high spatial frequency inputs.

Transparent amorphous germanium (a-Ge) has emerged as a promising material for engineering nanostructures and metasurfaces, offering significant potential for enhancing the performance of photonic devices in the short-wavelength infrared (SWIR) spectrum. Herein, the successful application of a-Ge metasurfaces with a truncated pyramid profile to enhance the external quantum efficiency (EQE) of a digital alloy Al_0.3InAsSb p–i–n photodiode across a broad-wavelength range in the SWIR is presented. The experimental findings demonstrate a broadband enhancement in EQE. Two metasurface samples are designed to emphasize different-wavelength ranges. Notably, 51% improvement in EQE at 1550 nm and 125% enhancement at 2000 nm is achieved. Finite-difference time domain simulations show that the observed EQE improvement originates from the reduction of reflection and electromagnetic field enhancement. This study underscores the promising role of a-Ge metasurfaces in advancing the capabilities of SWIR photodetectors. It lays the groundwork for further exploration in optoelectronic device enhancements.

Structural colors based on metasurfaces outperform traditional pigments and dyes in terms of nonfading, high spatial resolution, and high stability, usually incorporating active materials for tunability. Liquid crystals (LCs) are suitable for tunable structural color design due to their large birefringence and fast modulation by external stimuli. However, most LC-integrated structural colors focus on tailoring the polarization angle of incident light to generate two colors and their mixing. Herein, a scheme of full-color generation based on a plasmonic metasurface integrated with LCs utilizing the combination of the polarization angle rotation effect of the twisted-nematic LCs and the refractive index modulation through the realignment of the LCs near the metasurface is demonstrated. Based on the proposed structural color method, full-color generation of a record color gamut of 60.7% standard Red Green Blue region, equivalent to 43% National Television Standards Committee area, in the LC-integrated metasurface, has been numerically realized by tuning the bias voltage of the LCs in reflection. The achieved color gamut is nearly 4 times wider than the previously reported result. The proposed active full-color generation metasurface shows great potential in applications for low-power reflective color display, anticounterfeiting, and optical encoding.

Quantum Well Lasers

Benefitting from the interaction of the GaAs/GaAsP strained quantum well and InAlAs active region dislocation blocking layer, in article number 2300348, Jian Li and co-workers show that the threading dislocation penetration to the quantum well region of the silicon-based quantum well lasers can be bended and blocked. By the introduction of this strain compensate stress control structure, the 850 nm room temperature continuous wave emitting silicon-based quantum well laser exhibits a 94.2 mW power output, a 715 Acm^–2 threshold current density, and enhanced reliability.

Active Tunable Terahertz Metamaterials

Metamaterials give terahertz technology a broader application prospect. Active control ability of terahertz metamaterials is highly valuable and captivating. In article number 2300351, Kai Chen, Degang Xu, and co-workers categorize four basic types of tunable terahertz metamaterials based on external stimuli. Mechanical modulation offers simple yet efficient modulation, while electrical and magnetic modulation provide convenient adjustment. Moreover, optical modulation focuses on incorporating various materials to high-speed control.

Terahertz (THz) radiation is highly promising for various applications, from industrial inspections to medical diagnoses. Given the typically ultralow-level power of generated THz radiation, the achievement of high responsivity in THz detection stands as a critical imperative for its applications. Graphene-based detectors have become an attractive choice for THz detection due to the graphene unique 2D material structure, allowing a broad absorption spectrum and ultrafast response. Various plasmonic antenna arrays are also employed to couple with graphene, compensating for its modest optical absorption. However, the configuration of the plasmonic antenna arrays plays a crucial role in THz detection as it determines the graphene physical mechanisms of photodetection, directly impacting the final responsivity. Here, the key factors for achieving high responsivity are investigated and it is presented that reducing the gap size of the plasmonic antenna arrays to the nanoscale and implementing a series-connection configuration can result in a remarkable increase in responsivity, often by several orders of magnitude. Importantly, this approach effectively prevents short circuits and minimizes dark current, further enhancing the overall performance of the detection system.

Polymer-network liquid crystal (PNLC) possesses both advantages of low-molecular-weight liquid crystal (LMWLC) and liquid crystal (LC) polymer. Herein, a two-stage polymerization strategy for the formation of unique PNLC with oxygen-sensing properties is reported. The reaction mixture consists of 6% diacrylate RM257, 93.5% LMWLC 4-cyano-4′-pentylbiphenyl (5CB), and 0.5% photoinitiator dimethoxy-2-phenylacetophenone (DMPA). In the first stage, the mixture is exposed to UV light for 2 min to form a primary polymer network, which is highly uniform with a planar orientation. However, some free radicals are trapped inside the LC due to the short UV exposure time. Subsequently, the trapped free radicals are released by heating the PNLC sample into an isotropic state. Under this condition, the free radicals can move freely and react with surrounding monomers to form a secondary polymer network, which is highly disordered and scatters light strongly. Because oxygen can deactivate free radicals trapped inside the PNLC, the phenomenon to detect oxygen and monitor the diffusion of oxygen through the PNLC is exploited. The PNLC-based oxygen sensor is potentially useful for the detection of oxygen and monitoring the exposure time to oxygen.