Optics letters最新文献

In this study, we demonstrate a hardware-efficient post-equalization implementation for PAM8 signals on an FPGA platform by utilizing an additive power-of-two (APoT) quantization scheme. This approach reduces hardware resource consumption by over 70% compared to conventional methods while preserving critical performance metrics. In a 300-m W-band wireless communication experiment, the system reliably transmits 22.1184 Gbit/s PAM8 signals and satisfies the 2.4 × 10^-2 soft-decision forward error correction (SD-FEC) standard. Notably, under a host-assisted workflow, the APoT scheme achieves performance equivalent to 16-bit uniform quantization and exhibits superior stability than PoT quantization.

We propose a scheme for dynamically controlling optical torque on Mie-sized particles using a single linearly polarized plane wave, assisted by a fixed coherent optical environment constructed from multiple interfering plane waves and designed using a back-propagation-based inverse design algorithm. Our design accounts for all physical mechanisms that can induce optical torque, rather than relying solely on spin angular momentum. Such an approach ensures an accurate one-to-one mapping between the polarization of the control wave and the resulting torque orientation. The method introduces an additional degree of freedom for dynamic and programmable torque control using simple, physically realizable plane waves and offers a strategy for polarization-encoded optical torque control.

After six years as Editor-in-Chief, Miguel A. Alonso will conclude his term, and Carsten Rockstuhl will take over the role on January 1, 2026. Just as the leadership of Optics Letters is changing, so are the publishing landscape, the field of optics and photonics, and the way in which scientists pursue their research activity. These changes prompted us to reflect on the past and future of the Journal in a permanently evolving environment.

We studied interference dislocations (forks) adjacent to an emission spot in an interference pattern. We observed the adjacent interference dislocations in emission of excitons in a monolayer transition metal dichalcogenide and in emission of spatially indirect excitons, also known as interlayer excitons, in a van der Waals heterostructure. Our simulations show that the adjacent interference dislocations appear due to the moiré effect in combined interference patterns produced by constituent parts of the emission spot. In contrast to interference dislocations in coherent states, such as interference dislocations due to quantized vortices in condensates, the appearance of adjacent interference dislocations does not require coherence between the parts of the emission spot, indicating that interference dislocations can be observed in a classical system. We show that the interference dislocations in classical systems can appear in interference images for various spatially modulated emission patterns.

Terahertz (THz) intensity modulation technology is crucial for future low-cost 6G networks but is vulnerable to jamming. While frequency hopping (FH) counters single-tone jamming, our evaluation demonstrates its weakness against modulated jamming. Specifically, we demonstrated that while FH with a 40 GHz carrier separation is effective against single-tone jamming, it fails against modulated jamming. To address the vulnerability, we propose a self-coherent THz system where the transmitter generates both the radio frequency and local oscillator signals. This architecture separates the desired signal from the modulated jamming for secure communication. Moreover, using wavelength-tunable lasers for FH, the system resists both modulated and single-tone jamming. We demonstrate secure 1-Gbit/s transmission at 275 GHz against a 235 GHz modulated jamming signal and the reverse case. This cost-effective scheme improves THz link resilience to multiple jamming types and supports secure THz wireless communications.

Single-shot fs laser-induced breakdown spectroscopy (LIBS) has the potential to capture ns-scale electrode desorption phenomena in pulsed power fusion drivers. However, the successful implementation of the diagnostic for this purpose is challenging, as it requires interpreting single-shot measurements collected from low-density gas mixtures. In this work, we demonstrate the efficacy of a Bayesian-optimized convolutional neural network (CNN) to interpret these measurements. We generated 256 distinct measurement conditions at relevant gas pressures ranging from 80-530 mTorr by mixing 100-250 sccm H₂ and 50-200 sccm CH₄ in increments of 10 sccm. Despite the considerable overlap between signals separated by 20 sccm, the CNN is able to predict the H₂ flow rate with a root-mean-square error (RMSE) of 15.9 sccm and the CH₄ flow rate with an RMSE of 12.0 sccm. The average relative prediction error is <9% for each gas and largely remains below or near 10%.

Compared to wide-field (WF) microscopy in the second near-infrared (NIR-II) window, NIR-II multifocal structured illumination microscopy (NIR-II MSIM) provides a twofold improvement in transverse spatial resolution, along with enhanced penetration depth and superior image contrast. These advantages position NIR-II MSIM as a promising platform for studying physiological processes in turbid specimens. However, significant background noise caused by cumulative photon scattering continues to severely degrade image resolution and fidelity. Moreover, the data processing workflow in NIR-II MSIM is highly sensitive to motion artifacts, which further limits its broader applications in live-tissue imaging. To address these challenges, we introduce NIR-II MSIM-eSRRF, a technique that combines NIR-II MSIM with enhanced super-resolution radial fluctuation (eSRRF). This hybrid approach facilitates advanced deep imaging with improved spatial resolution and contrast across turbid specimens, including Intralipid phantoms, ex-vivo pork tissue, and live mice. Notably, NIR-II MSIM-eSRRF could effectively suppress motion artifacts, yielding nearly artifact-free visualization of fine cerebral vessels in vivo. As such, the NIR-II MSIM-eSRRF platform will emerge as a powerful tool for investigating physiological processes in highly scattering environments, thereby accelerating advancements in intravital fluorescence microscopy.

Hopfield neural networks, classic examples of associative memories, are well-established models for pattern storage and retrieval. However, the original Hopfield network, characterized by quadratic interactions among neurons, exhibits limited storage capacity. To enhance this capacity, researchers have introduced nonlinear functions-such as polynomial and exponential functions-to generalize the network's energy landscape. In this work, we propose an optical implementation of the Hopfield network that employs optical parametric amplification to realize a hyperbolic interaction function. We numerically simulate the pattern storage and retrieval dynamics of our optical model and compare its storage capacity with that of Hopfield networks using polynomial interaction functions. Our results show that the storage capacity of the proposed model increases exponentially with the number of neurons and depends on optical parameters such as pump laser power and nonlinear medium properties. This dependence enables further enhancement of storage capacity by tuning the physical hardware alone, without modifying the network architecture.

This study proposes a fiber chromatic confocal method with a 2D spectral demodulation to improve the axial resolution, which is achieved by the cross-dispersion of an echelle grating and prism. A chromatic confocal axial response model is derived based on confocal imaging and grating diffraction theories. The model parameters are fitted using calibration data, thereby facilitating the decoding, intensity correction, and reconstruction of the spectrogram to convert the 2D spectral peak accurately into the measured position. Experimental results show the axial resolution of 0.1 μm for the fiber probe with a measurement range of 3 mm, doubling the performance of conventional 1D spectral demodulation methods. This improvement demonstrates the applicability of the proposed method for high-precision measurement requirements, such as the assembly and testing of aeroengines.

In optical imaging and sensing applications, reliable and efficient medical image encryption is essential for secure transmission. This work proposes a novel, to the best of our knowledge, security scheme that integrates a bio-interactive system (predator-prey model), compression techniques, and multi-directional diffusion, with emphasis on compatibility with optical sensing. Dynamic characteristics of the bio-interactive system are analyzed to confirm high randomness suitable for encryption. Based on compressive sensing principles, a dynamic threshold is introduced and a measurement matrix constructed via bio-interactive system to enhance reconstruction quality. A multi-directional diffusion mechanism is furtherly designed, which spreads along rows, columns, and diagonals, thereby enhancing diffusion affect. This scheme is verified to feature high key sensitivity, strong robustness against computational attacks, and efficient performance suitable for real-time optical medical image encryption.