Optics express最新文献

The integration of multiband transmission channels with broadband radar cross-section (RCS) reduction is a pivotal yet challenging goal for advanced stealth radomes. This paper proposes a frequency-selective binary metasurface (FSBM) that synergizes a binary coding metasurface with a frequency-selective surface (FSS) to simultaneously achieve high-selectivity dual-passband transmission and wideband RCS suppression. The top-layer binary metasurface, composed of two artificial magnetic conductors (AMC) units arranged in an optimized sequence, facilitates destructive interference for broadband backscattering suppression. The bottom-layer FSS, functioning as a second-order dual-band filter with aperture-coupled resonators, provides the desired passbands and acts as a near-perfect electric conductor (PEC) reflector in the stopband to enable AMC operation. A prototype is fabricated and measured, demonstrating two transmission bands at 5.14 GHz and 7.61 GHz with low insertion loss (IL) and steep roll-off, alongside a fractional bandwidth exceeding 76.3% for -10 dB RCS reduction. This work presents a viable path forward for developing low-scattering platforms for multiband radar and communication systems.

In this article, we propose a tunable multilayered resonator (TMR) to achieve broadband high-sensitivity sensing within a deep-subwavelength structure. The proposed TMR significantly enhances the incident electric field for Rydberg atoms, improving the sensitivity of the room-temperature atomic sensor. Additionally, by incorporating varactor diodes, the resonant frequency of the TMR can be dynamically controlled by adjusting the diode bias voltage. In the experiment, the TMR realized a 45.26% relative bandwidth, ranging from 13.19 MHz to 19.16 MHz. Furthermore, the sensitivity of the system reached 0.13 µV/cm/Hz in the presence of the TMR at 19.16 MHz, compared to only 24.59 µV/cm/Hz without the TMR.

With the increasing speed of vehicles, the influence of aero-optical transmission effects on airborne optical imaging has become increasingly critical. An important aspect of aero-optical aberration research is to develop prediction models that can estimate such aberrations under various flight and imaging conditions, thereby providing prior information for aberration correction. However, due to the multitude of influencing factors, reliable prediction models are still lacking. In this study, a method for constructing prediction models of aero-optical aberrations is introduced, derived from the similarity of aero-optical transmission aberration, which itself is based on the principle of flow similarity in the inviscid core region of supersonic flows. The proposed model is validated using a side-window blunt-cone vehicle at Mach 3, with 0^∘ angle of attack and 0^∘ line-of-sight angle. Computational results show that within the altitude range of 6km to 20km, the weighted Rw2 value for the linear fit between aero-optical aberration and free-stream density reaches 0.9973, indicating the model's exceptional predictive accuracy.

Thermogenetics is a bioengineering technique that enables control of cellular activity via temperature-sensitive ion channels and externally applied heating. We present a fiber-optic platform for infrared laser thermogenetic stimulation combined with the simultaneous optical readout of fluorescent biosensors and temperature in the brain of freely moving animals. Infrared light delivered through a reconnectable double-clad optical fiber enables spatially localized heating of neural tissue, eliciting reproducible behavioral responses via the human transient receptor potential vanilloid 1 (hTRPV1) channel. The same platform supports multimodal optical measurements, including all-optical thermometry based on nitrogen-vacancy (NV) centers in diamonds and dual-wavelength excitation fluorescence detection. The temperature was retrieved from the zero-phonon line (ZPL) of NV^- fluorescence, providing an experimentally demonstrated sensitivity of 16 mK·Hz^-0.5, with a shot-noise-limited performance reaching 1.2 mK·Hz^-0.5. This integrated and scalable approach allows for precise thermal neuromodulation while enabling flexible integration with genetically encoded fluorescent sensors.

This study presents the design, modelling, and implementation of a high-efficiency, linearly polarized Nd:YAG laser operating at 1064 nm, based on what we believe to be a novel coupled ring-linear cavity configuration with diode side-pumping. To overcome the challenges of unpolarized emission and thermal lensing in side-pumped solid-state lasers, a side cavity containing a Brewster window was integrated, enabling quasi-unidirectional operation and enhanced polarization purity. A 50% increase in output power was achieved compared to the conventional ring cavity, while the polarization conversion efficiency reached up to 82%. The thermal lens focal length was characterized both experimentally and via LASCAD simulation, showing close agreement (e.g., 760 mm vs. 802 mm at 13 A). Comprehensive stability analysis using the ABCD matrix method and LASCAD simulations guided the optimization of cavity geometry, minimizing astigmatism and ensuring mode stability. Experimental validation demonstrated near-diffraction-limited beam quality with M² ≈ 1.2, measured according to ISO 11146-1:2005. In addition, optimal positioning of the nonlinear crystal (99 mm from M4) was identified for efficient second harmonic generation. This coupled cavity strategy offers a robust and scalable solution for generating high-power, polarized beams in solid-state lasers, particularly benefiting applications in nonlinear optics, frequency conversion, and single-frequency operation.

Reflections in semiconductor optical amplifiers (SOAs), especially in heterogeneously integrated silicon photonics platforms where isolators are absent, can severely degrade performance through nonlinear gain dynamics and excess noise. Even weak reflections can induce backward-propagating fields that can coherently interfere with the forward-propagating signal, causing forward gain suppression resulting from reflection-induced carrier depletion. Existing models, which primarily focus on unidirectional propagation, do not adequately address the dynamic noise generated by this bidirectional coupling. In this work, we present a self-consistent bidirectional model that includes nonlinear gain saturation, phase-sensitive interference, and the resulting excess intensity noise. We show that modest chip-level reflections, when combined with mechanical vibrations, thermal drift, current noise, or laser phase jitter, can elevate excess intensity noise to levels approaching the fundamental amplified spontaneous emission (ASE) noise floor, making it necessary to account for its effect in system design and performance evaluation. This framework enables predictive modeling of reflection-sensitive behavior, providing a valuable tool for optimizing active photonic devices, particularly in heterogeneously integrated III-V/Si platforms.

A self-starting all-fiber Mamyshev oscillator (MO) at 1550 nm is proposed and experimentally demonstrated based on an absorption filter. A shortpass absorption filter is designed based on the strong absorption of Tm³⁺ ions near 1560 nm. The filter is cascaded with a conventional fiber filter, forming an offset spectral filtering stage suitable for MO. The effects of the cutoff depth of the absorption filter and the pump power on the self-starting mode-locking behavior of MO are systematically investigated. Experimental results show that self-starting mode locking is achieved when the pump power in both arms reaches 390 mW. With further pump power scaling, ultrashort pulses with an energy of 6.52 nJ, a pulse duration of 225 fs, and a 20-dB spectral bandwidth of 375.6 nm, an overall spectral bandwidth of 502 nm are generated. The MO also demonstrates excellent self-starting performance. The MO can operate without seed injection or auxiliary starting arms. The straightforward design can enable a novel implementation of a high-energy ultrafast fiber laser.

High-dimensional quantum systems offer a number of advantages in larger information capacity, stronger noise resiliency, higher efficiency, and accuracy over the qubit systems. In quantum communication, the maximally entangled states will inevitably become mixed states or less-entangled pure states due to the channel noise during practical transmission or storage. We propose a universal scheme to concentrate nonlocal high-dimensional generalized Bell states with unknown parameters. After the cross-Kerr nonlinearities, X-quadrature homodyne measurements, and single-partite projection measurements are performed only at Bob's site, a two-qutrit maximally entangled Bell state can be distilled, while previous entanglement concentration protocols (ECPs) mostly focused on two-level qubit systems. The concentrated partially entangled qubit states, reserved as the by-product, are the fascinating resources for some quantum information processing tasks. Moreover, single-qutrit projection measurement, the key ingredient for our ECP with unknown parameters, is completed by using linear optical elements. Additionally, linear optical high-dimensional ECP with known parameters is also designed.

Room-temperature solid-state III-nitride quantum dots (QDs) are an emerging platform for UV-visible quantum light sources. Despite the potential, a unified theoretical framework linking QD microscopic dynamics with nanophotonic structures remains unexplored. In this study, we develop a comprehensive computational study that bridges quantum mechanical modeling of III-nitride QDs with nanophotonic inverse design for optimized single-photon sources. By modeling the III-nitride QD dynamics as a biexciton-exciton cascade in a four-level system coupled to a cavity, we evaluate the impact of QD-cavity coupling, cavity detuning on QD dynamics, and analyze how dissipation and decoherence channels degrade photon indistinguishability. We demonstrate that by tuning the cavity resonance to the biexciton-exciton transition and engineering the Purcell factor, high indistinguishability (>99%) can be achieved in the weak coupling regime. However, entanglement concurrence is strongly limited by fine-structure splitting and cannot be recovered through Purcell enhancement alone. Guided by these insights, we use computationally efficient adjoint-based inverse design to numerically develop a suspended GaN nanobeam cavity waveguide that meets target parameters while enabling efficient photon extraction. This study reveals a fundamental trade-off between indistinguishability and photon extraction efficiency, and shows that a Purcell factor of ∼100 - with two-sided extraction efficiency of up to 66% - can be achieved with a 12-hole integrated photonic waveguide. These results provide guidelines for the co-design of integrated III-nitride quantum light sources for on-chip photonic circuits.

Strain engineering has become a key method for tuning the optical properties of two-dimensional transition metal dichalcogenides by deforming their crystal lattice. In this study, we demonstrate how localized strain engineering can enhance trion emission at precise points with maximum strain, by using nanopillar arrays. At room temperature, by applying non-homogeneous biaxial strain, we create a potential energy landscape that efficiently converts excitons into trions, resulting in a well-defined two-peak structure in the photoluminescence (PL) spectrum. At cryogenic temperature, we observe sharp localized emission peaks, indicating highly confined excitons at strained lattice sites. By comparing strain-induced emitters at nanopillar sites with random native defects, we experimentally demonstrate that strain can effectively control the density and emission energy of localized emitters, providing a pathway for the deterministic formation of localized emitters with precise energy.