Optics letters最新文献

We compare the nonlinear magneto-optical rotation (NMOR) effect in a single-beam probe scheme and a two-beam Raman-coherence-assisted scheme using cold rubidium atoms produced with an integrating sphere apparatus. In both schemes, NMOR arising from D1 and D2 excitation combinations was studied. We show that adding a Raman-coherence manipulation laser can substantially increase the NMOR, and the largest NMOR enhancement occurs when both probe and Raman-coherence lasers couple the same D2 transitions with different detunings. For far-off resonance excitation with a weak probe laser, we show that the Raman-coherence-assisted NMOR enhancement can be about 6 times larger than the single probe scheme operated under the same conditions. The Raman-coherence-enhanced NMOR is also shown to be substantially larger than that from an optically pumped magnetometer using a single strong circularly polarized probe.

A method is proposed for calculating the periodic backdrops that cover the entire field of view in full-parallax high-definition computer-generated holograms (FPHD-CGHs), which can reconstruct very deep 3D scenes without any vergence-accommodation conflict; however, the reconstructed 3D images commonly appear to be floating in empty space, because the computational resources needed to calculate a large backdrop or wallpaper are extremely high. The proposed method expands the apparent sampling window of a backdrop's wavefield using convolution-based numerical propagation with circular convolution. A technique based on the conventional silhouette method is also proposed for occlusion processing in the expanded background. An actual FPHD-CGH was fabricated to demonstrate the validity of the proposed method.

Flexible integrated photonics holds great potential for a wide range of applications beyond the capabilities of conventional rigid platforms. A mechanically bending nanolaser with an ultra-small mode volume and low power consumption could serve as a key building block for ultra-compact flexible photonic chips. Here, we present a curved-shape topological photonic crystal semiconductor nanolaser in the telecom C-band with a low lasing threshold of 4.5 kW/cm². Multi-wavelength lasing operations are observed in the fabricated nanolasers by slightly tuning the optical pump positions at the topological interface, demonstrating that higher-order modes can be selectively excited for lasing emission. The demonstrated bending topological edge-state nanolasers provide a promising approach toward ultra-compact light sources for flexible photonic chips.

We propose a single-layer quadratic phase-transmissive metasurface (MS) that enables continuous wavelength-controlled lateral focus scanning under oblique incidence. By employing a laterally translated quadratic phase profile, the focal spot of obliquely incident light is positioned on the optical axis of the MS at the designed center incident wavelength. As the incident wavelength varies, the focal position shifts laterally on the focal plane. This operation provides precise and rapid lateral focus control without mechanical motion or active tuning elements. Additionally, the design incorporates a large depth of focus (DOF), ensuring stable focusing performance and maintaining a nearly constant focal spot size across the entire operating wavelength range. The fabricated device was experimentally characterized across the C- and L-bands from 1530 to 1600 nm, achieving a lateral scan range of 321 µm and a stable focusing efficiency of approximately 55%. This compact, vibration-free MS provides a high-speed, broadband platform for focal control.

Advances in modern optical technology are driving increasingly stringent requirements for the precise controllability of structured-light fields. However, existing structured light fields struggle to achieve synchronous yet independent control over both curved propagation trajectories and axial rotation within a single beam. To address this challenge, we propose and experimentally demonstrate a novel, to the best of our knowledge, structured beam, termed the fifth-order phase-controlled rotating self-bending beam (5th-PRSB). The 5th-PRSB enables simultaneous control of parabolic trajectory and rotation by superimposing two Bessel vortex beams with distinct phase velocities and opposite topological charges, along with a fifth-order homogeneous phase for composite modulation. Experimental results confirm that the 5th-PRSB enables parallel capture of multiple particles and their stable arrangement into arrays, underscoring its potential for applications in precision optical manipulation and microrobotics.

Single-photon imaging presents a promising solution for imaging in dense scattering media. Yet, existing methods predominantly rely on per-pixel photon count histograms for preprocessing, which treat pixels separately and neglect intrinsic spatio-temporal correlations. This is an inherent limitation that is drastically amplified by scattering effects, which diffusively spread signal information across adjacent pixels simultaneously. To capture these global correlations, we propose a histogram-free SPAD array sensing method that directly exploits the raw photon arrival sequences. Specifically, we design a multi-head LSTM sequence model with a dual-task training objective to jointly optimize classification and depth regression. Our approach is validated by extensive experiments on a self-constructed dataset, acquired via a real-world hardware prototype under varying fog densities. Our histogram-free approach outperforms complex baselines in scattering environments by preserving temporal information, while its lightweight design enables efficient deployment in resource-constrained systems.

Photolithography is essential for integrated circuit fabrication, where exposure determines pattern transfer and affects subsequent development and etching. Conventional methods like AFM and SEM are ex situ and cannot isolate exposure dynamics. To overcome these limitations, we introduce LithoPhase, an in situ monitoring system for photolithographic exposure that, to our knowledge, represents the first employment of quantitative phase imaging to track the photolithographic exposure process. Experimental results demonstrate that LithoPhase tracks phase evolution with micron-scale spatial and millisecond temporal resolution. Thus, LithoPhase enables real-time, in situ monitoring of exposure dynamics, offering a viable approach for advanced photolithography.

2D optical phased arrays (OPAs) face a fundamental tradeoff between large scale and wide field of view (FOV), as scaling the array requires greater antenna spacings, which constrains the FOV. We report a mode-division multiplexing (MDM) based 2D OPA that simultaneously supports both large-scale design and wide FOV for beam steering. By employing a single waveguide bus and encoding routing information into distinct waveguide modes, the architecture eliminates dense inter-pixel waveguide pathways, thereby reducing spatial footprint and extending the attainable FOV. Our proposed MDM-OPA depicts 11.2° × 11.2° FOV at λ = 1.55 μm and supports an array scale of 16 × ∞ (theoretically unlimited). Moreover, the simulated maximum insertion loss for all radiating pixels remains below 3 dB across the entire C-band. Owing to its high scalability, the proposed design can be further optimized for even larger FOV and array dimensions, making it a promising platform for free-space optical communication and LIDAR applications.

Radially self-accelerating beams (RSABs), owing to their rotating propagation and orbital angular momentum (OAM) properties, have found applications in optical micromanipulation and optical metrology. However, conventional RSABs exhibit fixed propagation behaviors, and existing shaping approaches often lack compatibility, restricting their applicability in complex real-world scenarios. In this work, we propose an angular-spectrum engineering approach based on Fourier optics, enabling the design and control of multi-degree-of-freedom RSABs (Multi-DoF RSABs) with programmable angular velocity, longitudinal intensity, three-dimensional trajectory, and OAM. Experimental results demonstrate independent adjustment of these four degrees of freedom, in agreement with theoretical predictions. This work provides a flexible framework for designing RSABs and highlights their potential for applications in optical manipulation and microfabrication.

Previous studies on topological dual-band frequency routers have focused on routing signals separately within two distinct frequency bands. However, the potential of dual topological bands has not been fully explored, particularly the possibility of each band supporting multiple frequency channels. Here, we propose a dual-band multi-frequency wave routing based on photonic square-root topological insulators. By introducing tailored perturbations into a decorated honeycomb lattice, we open two band gaps and design two distinct topological interfaces to obtain multi-frequency topological edge states. As a result, our single structure enables the routing of four different frequency ranges. This work provides a new approach for advanced integrated devices based on photonic square-root topological insulators.