Optics express最新文献

The knowledge of the exact structure of the optical system point spread function (PSF) enables a high-quality image reconstruction in fluorescence microscopy. Accurate PSF models account for the vector nature of light and the phase and amplitude modifications. Most existing real-space-based PSF models fall into a sampling pitfall near the center position, yielding to the violation of energy conservation. In this work, we present a novel, to the best of our knowledge, Fourier-based techniques for computing vector PSF and compare them to the state-of-the-art. Our methods are shown to satisfy the physical condition of the imaging process. They are reproducible, computationally efficient, easy to implement, and easy to modify to represent various imaging modalities.

Within a closed system, physical interactions are reciprocal. However, the effective interaction between two entities of an open system may not obey reciprocity. Here, we describe a non-reciprocal interaction between nanoparticles which is one-way, almost insensitive to the interparticle distance, and scalable to many particles. The interaction we propose is based on the non-conservative optical forces between two nanoparticles with highly directional scattering patterns. However, we elucidate that scattering patterns can in general be very misleading about the interparticle forces. We introduce zeroth- and first-order non-reciprocity factors to precisely quantify the merits of any optomechanical interaction between nanoparticles. Our proposed one-way interaction could constitute an important step in the realization of mesoscopic heat pumps and refrigerators, the study of non-equilibrium systems, and the simulation of non-Hermitian quantum models.

The discovery of bound states in the continuum (BIC) of optical nanostructures has garnered significant research interest and found widespread application in the field of optics, leading to an attractive approach to achieve high-Q (Quality factor) Fano resonance. Herein, an all-dielectric metasurface consisting of four gallium phosphide (Gap) cylinders on the MgF₂ substrate is designed and analyzed by the finite element method (FEM). By breaking the symmetry of the plane, specifically by moving the two cylinders to one side, it is possible to achieve a transition from the symmetry-protected BIC to quasi-BIC. This transition enables the excitation of sharp dual-band Fano resonance at wavelengths of 1,045.4 nm and 1,139.6 nm, with the maximum Q factors reaching 1.47 × 10⁴ and 1.28 × 10⁴, respectively. The multipole decomposition and near-field distributions show that these two QBICs are dominated by the electric quadrupole (EQ) and magnetic quadrupole (MQ). Furthermore, bidirectional optical switching can be accomplished by changing the polarization direction of the incident light. As a result, the maximum sensitivity and figure of merit (FOM) are 488.9 nm/RIU and 2.51 × 10⁵ RIU^-1, respectively. The results enrich our knowledge about BIC and reveal a platform for the development of high-performance photonics devices such as optical switches and sensors.

We present a novel configuration for broadband, wavelength-shift-free optical phase conjugation (OPC) utilizing four-wave mixing in a nonlinear fiber optical loop mirror (NOLM). In the proposed configuration, the input signals and the pump wave return to the input port of the NOLM whereas the phase-conjugated signals generated in the NOLM loop are transmitted through the output port. This allows the phase-conjugated copies to occupy the same wavelength band as the input signals, in line with the requirements for practical deployment of OPC in communication links. The demultiplexing of the phase conjugates from the input signals sharing the same band is achieved by imparting an asymmetric phase shift on the pump via a fiber Bragg grating. We experimentally demonstrate waveband-shift-free OPC with an extinction ratio between signals and conjugated copies at the NOLM output of 17 dB to 25 dB across a band of 35 nm. Whilst a 7-nm wide performance gap exists in the middle of the band, this is the record bandwidth for waveband-shift-free OPC in an all-fiber setup. We compare the experimental results with numerical simulations of the OPC-NOLM, identify the reason for the observed performance gap, and justify the route for further performance improvement.

The coupling of the energy stability and spatial uniformity of the laser beam before and after second harmonic generation (SHG) was analyzed. SHG experiments were performed using a Nd:YAG nanosecond laser and LBO crystals, and images, pulse shapes, and energies were measured. The relationship between energy stability and spatial uniformity uses a formula derived from the previous study to analyze changes in energy stability and spatial uniformity of the input beam and converted beam. In addition, the measured input beam shape and energy are compared with the results of applying the SHG converting equation considering pump depletion. Both methods were similar to the experimental results when corrected by empirical factors. Through SHG, it was confirmed that there is an optimal point of energy stability and spatial uniformity of the laser beam near the critical power.

Polarization splitter-rotators (PSRs) are the key elements to realize on-chip polarization manipulation. Current PSRs on thin film lithium niobate (TFLN) rely on sub-micron gaps to realize mode separation, which increases the difficulties of lithography and etching. In this paper, a PSR on TFLN based on multimode interference (MMI) is demonstrated. Mode division is achieved by an MMI-based mode demultiplexer. The minimum feature size of the PSR is 1.5 µm, which can be fabricated with low-priced i-line contact aligners. Experimental results show a polarization extinction ratio (PER) > 16 dB and an insertion loss (IL) < 1.0 dB are achieved in a wavelength range of 1530-1578 nm for TE-polarized light. And a PER > 10.0 dB and an IL <2.1 dB are achieved in a wavelength range of 1530-1569 nm for TM-polarized light. This PSR could find application in the low-cost fabrication of dual-polarization TFLN-integrated photonic devices.

This study proposes a combined axicon (CA) design method based on a structural parameter optimization algorithm designed to rapidly address the demands of practical application scenarios, precisely tailor structural parameters, and produce high-quality Bessel beams (HQ-QBBs) that satisfy specific requirements. Compared to generating an HQ-QBB using an axicon, our method effectively overcomes the shortcomings of fewer tunable factors, a large number of high-energy side-lobes, and limited non-diffractive regions. Through detailed analyses of the transmission characteristics, imaging characteristics, and thick-sample detection ability of the generated HQ-QBB, the significant advantages of the proposed method are demonstrated. The proposed method is not only relevant to current research but also demonstrates wide-ranging application potential in future lens designs.

A misprint in our manuscript published in Opt. Express32(5), 7030 (2024) 10.1364/OE.505995 has been reported and corrected.

The periodic structures are widely studied in numerous optical applications and there is a number of good tools for numerical modeling of such a structures (for example rigorous coupled-wave analysis, finite-difference time-domain, finite element method etc.). However, when it comes to the modeling of incoherent effects in many cases of practical interest, the current methods are not rigorous enough or depend on computationally demanding averaging of coherent response. In this paper, we present a novel approach to modeling of incoherent effects in structures with lateral periodicity based on scattering matrix formalism, as a way to describe optical response of a structure, and on application of incoherent wave summation in the form of infinite geometric series and generalized Mueller matrix calculus. This method can be combined with any of the existing coherent methods of modeling periodic structures and it offers significantly faster computational performance than partially coherent/incoherent methods based on averaging. It is compared with other methods for modeling of incoherent effects and also with experimental spectroscopic data. This method is then used to explain phenomena emerging from the complex interaction between diffraction grating and thick substrate.

In this study, we investigate the feasibility of designing reconfigurable transmitting metasurfaces through the use of Drude-like scatterers with purely electric response. Theoretical and numerical analyses are provided to demonstrate that the response of spherical Drude-like scatterers can be tailored to achieve complete transmission, satisfying a generalized Kerker's condition at half of their plasma frequency. This phenomenon, which arises from the co-excitation of the electric dipole and the electric quadrupole within the scatterer, also exhibits moderate broadband performance. Subsequently, we present the application of these particles as meta-atoms in the design of reconfigurable multipolar Huygens metasurfaces, outlining the technical prerequisites for achieving effective beam-steering capabilities. Finally, we explore a plausible implementation of these low-loss Drude-like scatterers at microwave frequencies using plasma discharges. Our findings propose an alternative avenue for Huygens metasurface designs, distinct from established approaches relying on dipolar meta-atoms or on core-shell geometries. Unlike these conventional methods, our approach fosters seamless integration of reconfigurability strategies in beam-steering devices.