Optics letters最新文献

The breather is an important emerging topic in nonlinear optics. In fiber lasers, the breather is generally achieved by tuning the loss of the laser system to search for the proper Hopf-bifurcation route. Here, we propose a simple and reliable method to generate breathing pulses, i.e., to introduce a controlled periodic transmittance, i.e., a periodic loss, within the laser that drives the mode-locked pulses to produce a synchronous periodic evolution. Therefore, we name this type of pulse as active breathing pulses. Experimental results show that the characteristic parameters of the active breathing pulses, e.g., the breathing ratio and breathing frequency, can be accurately controlled by the modulation depth and modulation frequency of the periodic transmittance introduced by the electro-optical modulator (EOM). Numerical simulations can reproduce the experimental phenomena. Our work not only gives a new, to the best of our knowledge, approach to modulate the characteristics of the breather but is also promising for the discovery of novel Hopf-bifurcation phenomena and soliton patterns in a periodically varying system.

Displacement based quantum receivers can beat the standard quantum limit and have gained increasing attention in recent years. The displacement operation value can be estimated and calibrated by using Fock states as probes. In this Letter, we focus on the impacts of thermal noise when preparing the Fock probes on the estimation performance. We first derive the density matrix and the photon statistics of the noisy displaced number state with a uniformly distributed displacement phase. Based on the derived density matrix, we then analyze the performance of estimating displacement operations by using the maximum likelihood estimation (MLE) method. To decrease the computational complexity of the MLE, we further derive an approximated probability density of the photon numbers under small displacement. Besides, the quantum Cramér-Rao bound (QCRB) is also derived to analyze the performance limit of the displacement estimation. Numerical results found that, though thermal noise can greatly degrade the MLE accuracy of the displacement operations, the performance advantage of using Fock probes still persists over classical coherent probes. Besides, we demonstrate that the MLE method based on Fock probes can well approach the QCRB when the displacement strength N_c ≤ ~1.

We show that programmable photonic circuit architectures composed of alternating mixing layers and active layers offer a high degree of flexibility. This alternating configuration enables the systematic tailoring of both the network's depth (number of layers) and width (size of each layer) without compromising computational capabilities. From a mathematical perspective, our approach can be viewed as embedding an arbitrary target matrix into a higher-dimensional matrix, which can then be represented with fewer layers and a larger number of active elements. We derive a general relation for the width and depth of a network that guarantees representing all N × N complex-valued matrix operations. Remarkably, we show that just two such active layers-interleaved with passive mixing layers-are sufficient to universally implement arbitrary matrix transformations. This result promises a more adaptable and scalable route to photonic matrix processors.

Quantum dot (QD) white light-emitting diodes (WLEDs) have been aimed at improving high-color gamut displays and solid-state lighting yet faced scrutiny due to the toxicity of Cd. We have successfully fabricated WLEDs with a high color rendering index of 93 via heavy metal-free multinary copper chalcogenide nanocrystals. The devices demonstrate a maximum luminance of 1062 cd/m² and a peak external quantum efficiency (EQE) value of 1.15%. Notably, these devices exhibit minimal efficiency roll-off, maintaining an EQE value of 1.09% even at elevated luminance levels (500 cd/m²). This investigation presents a compelling methodology for fabricating WLEDs and holds significant promise for potential applications.

The applications of single-pixel imaging (SPI) and optical multiplexing techniques in optical encryption are gradually increasing. However, little attention has been given to integrating these two for applications. Here, we propose a dual-layer optical encryption scheme that combines sample region-dependent SPI and structured light multiplexing holography. In the encryption process, the bucket signal obtained by SPI and the position coordinates used to generate the structured illumination patterns for SPI will be encrypted into a holographic ciphertext through spatial-structured light multiplexing holography. During decryption, the bucket signal can be retrieved from the ciphertext using a binary matrix key, and the sampling region can be determined by illuminating the ciphertext with multi-ramp helical-conical beams. Thus, the original secret image can be successfully decrypted. This work takes advantage of the spatial mode multiplexing characteristics of the structured beams and the dependence of Fourier SPI encryption on the sampling region, thereby promoting the collaborative application of the two in the field of optical security.

Super-resolution structured illumination microscopy (SR-SIM) performs spectral expansion of high-frequency information encoded in stripe patterns. However, using a limited number of pattern orientations (typically three) results in a petal-like frequency spectrum, leading to structural and intensity fidelity degradation in reconstructed images. In this Letter, we propose an integrated spatial-frequency domain SIM reconstruction method that enables isotropic spectrum expansion, called ISO-SIM. ISO-SIM overcomes structural artifacts caused by an anisotropic spectral expansion in traditional SIM imaging. We demonstrate the feasibility and fidelity of ISO-SIM through simulations, Argolight slide, and live-cell imaging. ISO-SIM enhanced structural similarity and reduced the error in the mean intensity ratio at certain spatial frequencies compared to Wiener-SIM. We further applied ISO-SIM to live-cell quantitative FRET imaging. ISO-SIM-FRET ensured that the measured FRET efficiency matched the ground truth, with a 19% reduction in the standard deviation compared to Wiener-SIM-FRET, maintaining intensity fidelity and enhancing the accuracy of quantitative analysis while suppressing artifacts.

This Letter presents a layered ternary message passing (LTMP) decoder for the low-density parity-check (LDPC) code tailored for 50G passive optical networks (50G-PON). The proposed decoder adopts a layered architecture, and a corresponding density evolution analysis that enhances error correction performance is introduced. Additionally, we propose an optimization method for parameter combinations, which effectively achieves stronger performance. Results indicate that the LTMP decoder achieves exceptional error correction capabilities for the LDPC code in 50G-PON, even under low-precision input conditions.

We demonstrate the first, to our knowledge, delivery of megawatt peak power, single-mode mid-infrared (MIR) femtosecond pulses at 5-6 μm using a silica-based anti-resonant hollow core fiber (AR-HCF). Benefiting from the light confinement inside the hollow core, the AR-HCF exhibits high damage thresholds, reliable power stability, efficient spatial beam self-cleaning, and pulse shape preservation. Pumped by a homemade LGS-based two-stage optical parametric amplifier generating high-power ∼200 fs pulses, the fiber achieves a maximum delivered peak power of 4 MW at 5.1 μm and 5 MW at 6.1 μm, with peak intensities reaching 100 GW/cm², despite fiber losses exceeding 2 dB/m. This flexible, meter-scale delivery system demonstrates exceptional potential for addressing the challenges of high peak power MIR laser delivery in precise, minimally invasive interventional ablation, particularly at resonant peaks such as amide-I (6.1 μm) and cholesterol esters (5.75 μm).

We measure the spectral fluorescence emitted by commercial pure-silica core and germanium-doped core fibers in the range of 760-860 nm and find that the broadband fluorescence that exists in the Ge-doped fiber can be avoided by adopting the pure-silica core fiber. Most importantly, we present a narrowband (∼1 nm FWHM) emission line characteristic of zirconia ferrules used in both commercial Ge-doped and pure-silica core fiber patch cables. The results of this work are significant to many applications in the fields of quantum optics and fluorescence spectroscopy, where strong pump light co-propagates with signals at the photon level.

We propose and demonstrate a broadband 3-dB power splitter based on a non-Hermitian triplet waveguide fabricated on a silicon-on-insulator (SOI) platform. By exploiting mirror symmetry, we show that the triplet can be decoupled into two virtual subspaces: a Hermitian subspace featuring a lossless zero mode and a non-Hermitian subspace supporting lossy modes. The zero mode, with its intensity equally distributed between the outer two waveguides, plays a crucial role in achieving broadband performance, effectively suppressing mode competition and maintaining stable splitting against dimensional errors. Experimentally, the 1-dB operational bandwidth of the splitter is confirmed to exceed 70 nm, ranging from 1480 nm to 1550 nm. Furthermore, this approach can be directly extended to any 1×n power splitter, providing a scalable and robust solution for photonic integration.