Advanced Optical Materials最新文献

Polarization-Sensitive Heterojunction Photodetector

In article number 2401306, Ziyi Fu, Jiayue Han, Jun Wang, and co-workers introduce a polarization-sensitive photodetector based on the ReS₂/SnSe₂ heterojunction, detailing the material synthesis and device fabrication. This self-powered detector demonstrates excellent optoelectronic and polarization detection performance. Additionally, its application in optical communication systems is validated. This research provides a novel and practical approach for developing energy-efficient, high-performance polarization-sensitive detectors.

Ultraviolet-B Persistent Luminescence of CaF₂:Gd³⁺

After exposure to X-ray, CaF₂:Gd³⁺ continued to emit ultraviolet-B luminescence peaking at 313 nm, corresponding to the ⁶P_7/2 → ⁸S_7/2 transition of Gd³⁺. By X-ray photoelectron spectroscopy measurements, the valence variation model was excluded to explain the persistent luminescence of CaF₂:Gd³⁺. Potential applications including static labeling and dynamic tracking were demonstrated depending on such ultraviolet-B persistent luminescence. For further details, see article number 2401320 by Leipeng Li, Jianrong Qiu, Yanmin Yang, and co-workers from Hebei University and Zhejiang University.

Owing to its peculiar non-diffraction, self-acceleration, and self-healing properties, the Airy beam has attracted a great deal of attention in various fields such as micro-manipulation, plasma generation, and optical microscopy. To date, it is still a challenge to generate nonlinear Airy beams with microstructure efficiently, thus limiting applications of such Airy beams. Here, a novel and efficient method for generating Airy beams is experimentally demonstrated by microstructure on a nonlinear crystal surface, which is fabricated by a focused ion beam (FIB) technique. The second-harmonic (SH) Airy beams are generated in the far field and characterize their intensity distributions, which agree well with theoretical results. Then, the self-accelerating and self-healing properties of the generated SH Airy beams are demonstrated. Besides, the normalized efficiency of SH Airy beams is measured at (1.44 × 10⁻⁵%W⁻¹), and compare the efficiency of different methods of generating nonlinear Airy beams, which shows the advantages of this method. The proposed method of generating nonlinear Airy beams shows great potential for integrated optics, optical micro-machining, and advanced imaging.

Janus Metasurfaces with Arbitrary Polarization Control

The first Janus metasurfaces demonstrate directionally asymmetric orbital angular momentum generation from arbitrary spin. Titania-based meta-atoms enable operation in the visible range, extending beyond prior demonstrations in microwave and mid-infrared regions. Meta-atoms provide local/global rotation and width control, achieving global directional multifunctionality tailored by the Jones matrix. This multifunctionality in a single-layer design surpasses previous approaches based on spatial multiplexing or vertical stacking, expanding its applicability across diverse domains. For further details, see article number 2401335 by Yao-Wei Huang and co-workers.

Optical physical unclonable functions (PUFs) have attracted considerable attention as an immediately exploitable cryptographic primitive for high-level hardware security attributed to their potential for implementing a large parameter space through the incorporation of robust optical phenomena. However, previous optical PUFs primarily relied on linear and single-channel optical processes, requiring an increase in the number of optical inputs (materials or wavelengths) in a monotonous manner to scale up challenge-response pairs. Herein, an optical PUF capable of nonlinearly expanding the parameter space to enhance the cryptographic strength through the selective adjustment of up- and down-conversion luminescence is introduced. The nonlinearity in the expansion of the parameter space originates from a random distribution of three types of microspheres, with their shells designed to exhibit various positional arrangements of upconversion nanoparticles and perovskite crystals. Because energy and photon interactions depend on their positional proximity and excitation power, adjusting the two excitation inputs into five power steps enables the single PUF to generate 30 unique cryptographic keys, which is 15 times greater than what a linear system can offer. The PUF also demonstrates high stability, maintaining its cryptographic performance when exposed to heat, moisture, and long-term laser excitation, underscoring its practical applicability in security protocols.

Due to the extraordinary chemical and physical properties, ternary chalcogenides with wide-range bandgap, unique structures, and exceptional photoelectric properties have attracted great interest recently. Among them, Chromium thiophosphate (CrPS₄) is a promising semiconductor with excellent optical, mechanical, and electronic properties and has a lower lattice symmetry resulting in significant in-plane anisotropy. Here, the polarization-dependent nonlinear optical (NLO) responses of CrPS₄ flake are investigated. Based on polarization-resolved Raman spectroscopy, which identifies the crystal axis of sample, the anisotropic linear absorption spectra, I-scan technique, and pump-probe measurements are utilized to investigate the optical absorption information of CrPS₄. The polarization-dependent NLO responses are found originating from the anisotropic optical transition probability. And the polar optical phonons play an important role in carrier relaxation processes. Furthermore, CrPS₄-based all-optical switches are proposed, which can modulate the transmittance of signal light (CW laser) by changing the polarization of switch light (fs laser). This work provides insights into polarization-dependent CrPS₄-based devices, which is important to promote the potential applications in optical modulator, versatile optoelectronic detection, and so on.

As terahertz (THz) technology has been widely considered as a key candidate for future sixth-generation wireless communication networks, THz modulators show profound significance in wireless communication, data storage, and imaging. In special, dynamic tuning of THz waves through 2D electron gas (2DEG) incorporated with a hybrid design of metasurface has attracted keen interest due to the combined merits of deliberate structural design, rapid switching speed and the process compatibility. Current meta-modulator enables very high modulation depth but encounter limited bandwidth. In this paper, by taking into account the co-functional effects of temperature and voltage-dependent dynamic control on transmission amplitude, a 2DEG-based GaN-on-Si modulator with two switchable operational states (or four modes) of active wave control is proposed. Under cryogenic temperature conditions, the proposed device exhibits prominent 2D plasmons characteristics with switchable transitions between the gated mode and ungated mode for active control. Under room temperature conditions, the proposed device exhibits non-resonance broadband spectra characteristics with tunable transitions between the linearity mode and depletion mode for transmission control. The scheme provides an option for the development of the actively tunable THz meta-modulator and paves a way for the robust multifunctionality of electrically controllable THz switching, and biosensors.

The interface between the hole transport layer (HTL) and perovskite in p-i-n perovskite solar cells (PSCs) plays a vital role in the device performance and stability. However, the impact of this interface on the vertical phase segregation of mixed halide perovskite remains insufficiently understood. This work systematically investigates the impact of chemical and electronic properties of HTL on vertical halide segregation of mixed-halide perovskites. This work shows that incorporating a poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA)/CuI_xBr_1-x bilayer as the HTL significantly suppresses light-induced vertical phase segregation in MAPb(I_0.7Br_0.3)₃. This work uses grazing-incidence X-ray diffraction (GIXRD) to capture the depth-resolved composition change of MAPb(I_0.7Br_0.3)₃ at the interface and within the bulk under illumination. By changing the illumination direction and the electronic properties of HTL, this work elucidates the roles of charge carrier extraction and interfacial defects on vertical phase segregation. The PTAA/CuI_xBr_1-x bilayer, with its synergistic passivation and efficient hole extraction ability, stabilizes the interface and bulk of the mixed halide perovskite layer and prevents phase segregation. This work underscores that synergetic passivation and efficient hole extraction pack a more powerful punch for arresting the vertical phase segregation in mixed-halide perovskite.

2D van der Waals (vdWs) heterojunctions exhibit facile fabrication process and tunable optoelectronic properties. However, suppressing interfacial charge traps and multifunctional photoresponse remain significant challenges. Here, the study designs a 2D multifunctional phototransistor based on ambipolar MoTe₂/graphene (Gr)/p-type SnS_0.25Se_0.75 double vdWs vertical heterostructure via alloy engineering. The middle Gr interlayer is pivotal in reducing interfacial charge traps, facilitating vertical photocarrier transportation, and enhancing light absorption coefficient. Under photogating effect, the trapped electrons in SnS_0.25Se_0.75 promote the photogating effect, resulting in the maximum photogain of 8084 and specific detectivity (D^*) of 8.2 × 10¹² Jones. Under photoconductive effect, a high responsivity (R) of 36.9 A W⁻¹ and D^* of 7.17 × 10¹¹ Jones are achieved. Under photovoltaic effect, the devices exhibit a remarkable R of 501 mA W⁻¹, D^* of 1.4 × 10¹¹ Jones. Notably, a self-driven photocurrent polarized ratio of 8 under 635 nm is achieved because of the anisotropic nature of SnS_0.25Se_0.75 and the effective double built-in electric fields. By varying the gate voltage, the polarization ratio can be modulated from 1 to 2.5, enabling reconfigurable polarized-sensitive detection. Above all, the designed heterojunction with multifunctional and reconfigurable polarization detection.