Abstract Recent years have witnessed widespread adoption of α -phase molybdenum trioxide ( α -MoO₃) in biosensing owing to its in-plane anisotropic characteristics. We propose a bifunctional surface plasmon resonance biosensor employing the Kretschmann configuration that operates in the visible to near-infrared wavelength range and demonstrates a bifunctional capability defined by two core features: (1) In the wavelength-interrogation mode, the in-plane anisotropy of α -MoO₃ allows active performance tuning— x -polarization achieves high sensitivity ( S x = 8250 nm RIU −1 ), while y -polarization achieves a high figure of merit ( FOM y = 570.89/RIU). (2) The same sensor configuration also supports robust resonance angle-shift detection, confirming its versatility as a multi-mode platform.

Abstract This paper presents the design, fabrication, and characterization of a broadband metamaterial absorber capable of optical switching between high-and low-absorbing states. The proposed metasurface exhibits a wide absorption bandwidth ranging from 13 to 17.3 GHz, maintaining a high absorption for wide incidence angles and for both transverse electric (TE) and transverse magnetic (TM) polarizations, demonstrating the polarization-insensitive performance. The metasurface is composed of periodically arranged unit cells integrated with photoresistors that enable tunable electrical resistance under optical illumination. When exposed to light, the photoresistors reduce their resistance, allowing the structure to achieve a high absorption. In the absence of illumination, the increased resistance suppresses the absorption response, effectively switching the metasurface to be a reflective state. This optically controllable behavior provides a simple and efficient approach for realizing dynamically reconfigurable metamaterial absorbers, offering potential applications in adaptive stealth technology, electromagnetic shielding, and tunable sensing systems.

Abstract In this article, we present a refractive index sensor based on Fano resonance that exploits the interaction between a nanoring resonator and a metal-insulator-metal (MIM) waveguide. Our structure consists of a coupling between a waveguide and two resonators: one in the form of a ring and the other of lateral type. The nano-ring resonator is formed by two half-ring segments that are coupled to the MIM waveguide. The transmission spectrum of the proposed coupled system reveals a distinct Fano-type resonance that responds sensitively to variations in the surrounding refractive index. The sensor demonstrates an estimated sensitivity of about 3200 nm/RIU, which is higher than that of other Fano resonance–based sensors reported in the literature. The sensor’s simple structural design facilitates fabrication and enables its use in numerous refractive index detection applications.

Abstract Phase unwrapping is one of the key problems in fringe projection profilometry (FPP). These years, CNN-based and Transformer-based models are widely used in FPP phase unwrapping. Unfortunately, the limitation of CNNs in long-range modeling capabilities prevent them from effectively extracting fine-grained features in wrapping phase images, while Transformer-based models struggle with efficiently handling long-range dependencies due to their local focus or computational demands. Recent studies demonstrate that Mamba, a novel selective state space model (SSM), achieves efficient modeling of long-range dependencies by dynamically adapting its parameters based on input context, particularly in tasks such as long-sequence modeling. Inspired by this, we propose a hybrid deep learning model integrating Res-UNet with Mamba (CNN-Mamba network, CMNet) for phase unwrapping of single-frame fringe patterns. First, a new dual-branch skip connection module based on Mamba is proposed named convolution weighted feature fusion SSM (Conv_WFF-SSM) is proposed, integrating Mamba’s selective state space mechanisms with multi-scale convolutional feature weighting to simultaneously address long-range interaction modeling and hierarchical feature preservation during phase expansion. Second, a parameter-free attention module (PFAM) is introduced into the encoder and decoder to reduce information loss caused by downsampling and upsampling operations without increasing network parameters. Finally, the iterative attentional feature fusion (IAFF) module integrated into residual block to instead of the ordinary sum operation for the first time. Experiments demonstrate the validity and robustness of the proposed technique.

Abstract This study presents an ultra-broadband epsilon-near-zero (ENZ) modulator constructed from graphene–black phosphorus hybrid structures. The key mechanism enabling broadband modulation with high modulation depth (MD) is the spectrally complementary ENZ responses of graphene and black phosphorus, where graphene provides a tunable ENZ condition in the visible (VIS) band, while black phosphorus exhibits an anisotropic ENZ response in the near- to mid-infrared (NIR-MIR) regime. Simulation results demonstrate that the proposed modulator functions efficiently over a continuous ENZ-enhanced field-confinement band from 400 nm to 18.63 μ m, spanning the VIS to MIR regions. The MD is significantly enhanced, particularly in the MIR regime due to the induced ENZ effect. In addition, the modulation bandwidth of up to 710 GHz is achieved. Our work highlights the potential to enhance MD across an ultra-broadband spectrum, facilitating future applications of optoelectronic devices that utilize hybridized two-dimensional materials.

Abstract Continuously tunable phase-gradient metasurfaces offer powerful capabilities for dynamic and adaptive optics, but their practical realization remains challenging due to the complexity of device control architectures, especially when compared to binary or discretely tunable systems. In this perspective, we outline a unifying framework that leverages inverse design principles to enable scalable implementation of reconfigurable metasurfaces. We begin by reviewing three core innovations from our earlier work on phase change material (PCM) based varifocal metalenses: thermal profile shaping via patterned doping, phase-gradient tuning through direct search optical inverse design, and pixel-level wavefront control using phase-change metasurface arrays. We then highlight recent advances that build upon these foundations: an analytical, geometry-independent thermal inverse design method for microheater profile customization; the generalization of phase-gradient tuning to alternative actuation mechanisms including coherent optical control; and the experimental realization of a mid-infrared (mid-IR) two-dimensional spatial light modulator (2D SLM) based on diode-integrated PCM metasurfaces. Together, these developments demonstrate a path from architectural insight to scalable implementation, opening new opportunities for high-performance, programmable optical systems in imaging, beam shaping, and beyond.

Abstract In this paper, a random fiber laser with tunable multi-wavelength actively Q-switched using embedded Sagnac filters and electro-optical modulator is proposed. In the experiment, pumping was used to provide gain, random fiber phase shift Bragg grating was employed as random feedback media, and an embedded Sagnac filter was utilized to achieve wavelength tuning and switching. The results demonstrated that under conditions of a pumping power of 250 mW, a first-stage pumping power of Er–Yb co-doped fiber amplifiers is 67 mW, and a second-stage pumping power is 200 mW, single and multi-wavelength (up to septuple-wavelengths) outputs can be stabilized by adjusting the polarization controller, with a minimum side-mode suppression ratio of 36.98 dB, and a single-wavelength tuning range of 5.3 nm. At the dual-wavelength outputs, multiple pulse sequences, such as single, dual, and triple pulses, are observed, and the pulse intensities increase and widths decrease with the increase of the pump power. The laser has potential applications in optical communication, optical sensing and medical technology.