Optics express最新文献

With quantum optical technologies advancing toward real-world deployment, their success depends on reducing the size, weight, and power (SWaP) of the laser sources that drive them. While photonic integrated circuit (PIC)-based lasers have emerged as promising replacements to traditional bulky lasers, achieving a PIC-based laser system that satisfies both optical and functional requirements demands a system-level co-design of optics, electronics, and software that has not yet been realized. Here, we demonstrate a low-SWaP, tunable, and narrow-linewidth laser system based on PICs and programmable control electronics for the 780 nm region of the near-infrared spectrum. By leveraging the Vernier effect between a Fabry-Pérot laser diode (FPLD) and a microring resonator (MRR), we design the PIC to serve as an external cavity to self-injection lock the FPLD, resulting in a tunable laser with narrow linewidth. We package this PIC-laser into a standard butterfly package and drive it using a custom digital laser controller with a user-friendly interface. We design the programmable control electronics to meet the specific requirements of a PIC-laser as well as enable advanced functionalities that support cutting-edge quantum and classical optical applications. The complete laser system, which also includes optical isolators and fiber coupling, achieves up to 9.5 nm coarse tuning, 50 GHz mode-hop-free fine tuning, 30 mW free-space output power (before isolators), kHz-level intrinsic linewidth, and over 50 dB side-mode suppression ratio (SMSR). To exemplify the applicability of our laser system for quantum technologies, we perform spectroscopy on rubidium D2 transition lines and frequency-lock it to the cycling transition for days in a non-controlled environment with significant temperature fluctuations. We envision that our compact, fully integrated laser system will be a key enabler for scalable and deployable quantum and classical optical technologies.

Semi-transparent photovoltaics can replace conventional solar control glass, particularly when fabricated by high-throughput sputter deposition. We demonstrate that a fully sputtered transparent layer stack with realistic solar cell properties and with an ultrathin germanium absorber provides nearly color-neutral transmission and a suitable reflectance spectrum. The optical constants of all layers are used to build an optical model of the stack, enabling analysis of color rendering, angular dependence, and overall appearance. A sample deposited with model-optimized layer thicknesses confirms the predicted color neutrality. A subsequent sensitivity analysis reveals that color stability is dominated by relative thickness variations of the AZO layers, while deviations in other layers play a secondary role. These results highlight the suitability of the proposed architecture for facade-integrated, visually unobtrusive solar power generation.

The Maxwellian-view near-eye display inherently delivers an always-in-focus image, which effectively mitigates the vergence-accommodation conflict. However, it suffers from a narrow eyebox. To overcome this challenge, we propose a Maxwellian augmented reality display architecture with an expanded eyebox, enabled by a non-mechanical liquid crystal beam steering module. Specifically, the beam steering module consists of multiple cascaded stages of stacked electrically switchable half-wave plates and Pancharatnam-Berry deflectors. For experimental validation, a proof-of-concept prototype is constructed to validate the feasibility of our proposal. Experimental results confirm that the system retains an always-in-focus image while providing 4 × 4 switchable viewpoints, thereby effectively expanding the eyebox from 3 mm × 3 mm to 12 mm × 12 mm.

As a key enabling solution for solid-state beam steering, optical phased array (OPA) technology holds significant potential in light detection and ranging (LiDAR) systems and free-space optical communication. In this work, we proposed a Vernier OPA transceiver implemented on a SiN-on-SOI platform that achieves simultaneous wide field of view (FOV) and high sidelobe suppression ratio (SLSR). The proposed design employs tailored power splitters to regulate channel intensity distribution and utilizes a Vernier architecture for enhanced lobe suppression within a compact 120-channel configuration comprising a 64-element transmitting array and 56-element receiving array. Meanwhile, beam transmission and reception are implemented using a SiN-Si double-layer grating antenna, which offers both a large emission aperture and high emission efficiency. Experimental results demonstrate a scanning FOV of 140° × 16° and a divergence angle of 0.725° × 0.056°. A peak SLSR of 27.15 dB is obtained at 0°, with an average SLSR of 20 dB over the full 140° FOV, which paves the way for full-field blind zone free scanning in autonomous driving applications. Furthermore, we experimentally validated the full-field ranging capability of the OPA transceiver in a frequency-modulated continuous wave (FMCW) system, achieving a long-range detection up to 50 meters while demonstrating its performance in 3D imaging applications.

Optical properties of multiple types of Ru thin films spanning the range from UV to IR are reported for the first time. We show that the refractive index of these monatomic metallic thin films is strongly affected by the film's crystallographic attributes. Specifically, conductivity in the infrared is observed to correlate strongly with the grain structure of the film. Thin film microstructure should therefore be considered in regard to the applicability of the referenced optical constants of metals. Accordingly, we present optical constants for a set of four Ru films, each having a different grain structure.

Assessing the risk of laser damage to optical components for the most demanding laser architectures, producing high average and peak laser powers, is critical to the engineering of these complex systems. The existing laser-damage tests for such optical components are based on probabilistic measurements that induce laser damage in a tested sample as their central element. Such methodologies are, clearly, not optimal as they damage the very components that they test. Here, we present a theoretical framework and identify the class of physical settings in which the risks of laser-induced damage can be quantified in a nondamaging way, i.e., without damaging the tested components. We show that, with the parameters of the laser driver adjusted in such a way that laser-damage events are rare, the multipulse laser damage probability can be expressed in closed form as a function of the laser fluence and the signal-to-noise-ratio of the laser driver. Whenever these solutions can be extended to include an adequate model of laser-induced material modifications, the risks of laser damage can be evaluated without damaging tests but based solely on suitably detailed prior data on the statistics of the laser driver and the properties of light-induced material modifications. We show that, despite the wide variety of physical processes that may contribute to multipulse laser damage, the key properties of laser damage can be understood, described, and predicted using intuitive, closed-form solutions for its statistical measurables. The developed approach is shown to provide an accurate, physically insightful fit for the vast experimental data collected under varying experimental conditions, with different laser sources and different samples, including the most recent multipulse laser-damage studies for multilayer dielectric coatings designed for high-power laser beamlines. The developed framework thus provides a powerful resource for the analysis of laser damage in strong-field multipulse laser - matter interactions. Envisioned applications include, but are not limited to, the design of optical components for laser fusion technologies.

Our ability to structure materials at the nanoscale has, and continues to, enable key advances in optical control. In pursuit of optimal photonic designs, substantial progress has been made on two complementary fronts: bottom-up structural optimizations (inverse design) discover complex high-performing structures but offer no guarantees of optimality; top-down field optimizations (convex relaxations) reveal fundamental performance limits but offer no guarantees that structures meeting the limits exist. We bridge the gap between these two parallel paradigms by introducing a "verlan" initialization method that exploits the encoded local and global wave information in duality-based convex relaxations to guide inverse design towards better-performing structures. We first illustrate this technique via the challenging problem of Purcell enhancement, maximizing the power extracted from a small emitter in the vicinity of a photonic structure, where ill-conditioning and the presence of competing local maxima lead to sub-optimal designs for adjoint optimization. Structures discovered by our verlan method outperform standard (random) initializations by close to an order of magnitude and approach fundamental performance limits within a factor of two, highlighting the possibility of accessing significant untapped performance improvements. We further validate this method using a planewave absorption example with a lossy dielectric, showcasing how verlan initializations can mitigate getting trapped by sub-optimal local minima in photonic inverse design problems.

Multipole expansion methods have been primarily used for analyzing the electromagnetic scattering from non-magnetic isotropic dielectric scatterers, and studies about the scattering from magnetic objects seem to be lacking. In this work, we used the multipolar expansion framework for decomposing the electromagnetic scattering by dielectric particles with magnetic properties. Magnetization current contributions were explicitly accounted for by using the vector spherical harmonics to compute the electric and magnetic multipole contributions of arbitrary order. The exact analytical expressions for the corresponding spherical multipole coefficients were employed, with the scattering efficiencies being used to distinguish the dielectric and magnetic contributions of each multipole. This enables the analysis of scattering from arbitrarily shaped, anisotropic, and inhomogeneous magnetic scatterers. It also provides a tool for studying non-reciprocal devices that exploit magnetic resonances in magnetic-dielectric materials. Calculations were made for an experimentally feasible system, namely for ferrite-based scatterers operating in the microwave regime. These materials are of interest in radio frequency (RF) applications due to their magnetic activity. We demonstrated analytically that the magnetic circular dichroism in a magnetic-dielectric scatterer in the Faraday geometry can be decomposed into individual multipole contributions. The analytical results indicate that multipole resonances associated with magnetization currents can be even stronger than multipole contributions from conventional dielectric currents. It is worth noting that these analytical results were verified through comparison with numerical results from finite element method (FEM) simulations in COMSOL Multiphysics.

Segmented primary mirror (PM) telescopes offer significant advantages over monolithic mirrors: scalability, modularity, ease of fairing, serviceability, and segment-level wavefront control. Achieving the scientific objectives of such observatories requires accurate wavefront sensing to support fine alignment, calibration, and long-term wavefront control. In this work, we explore double blind Fourier holography (DBFH) as a high-precision wavefront sensing scheme and its relevance for future space observatory flagship missions such as the Habitable Worlds Observatory (HWO). DBFH has previously been applied successfully to challenging phase retrieval problems, including electron diffraction in crystallography and attosecond pulse characterization. Using DBFH, we numerically demonstrate full wavefront reconstruction for a segmented aperture consistent with HWO geometry from as few as four carefully selected focal-plane captures, achieving estimation precision approaching the picometer regime, with segment piston errors as low as 13 picometers in the presence of measurement noise. Finally, DBFH is algebraically linear, and as such, has the potential to reduce computational costs and avoid convergence pathologies common to nonlinear, iterative phase-retrieval (PR) methods. While demonstrated in the context of the HWO, this scheme is broadly applicable to high-precision wavefront sensing in any segmented PM telescope.

We demonstrate the first large-core Er: ZBLAN fiber-based chirped-pulse amplification system operating at ∼2.79 µm. Single-mode amplification in a coiled 46 µm-core, ∼0.064 NA Er:ZBLAN fiber delivers up to ∼144 µJ of stretched femtosecond pulses (∼1.5 ns) at a 5.5 kHz repetition rate. After diffraction-grating compression, ∼70 µJ pulses with a duration of ∼525 fs are obtained. This represents what is believed to be a new record pulse energy for femtosecond-duration Er: ZBLAN fiber lasers, exceeding previous results by nearly two orders of magnitude. The performance is enabled by a diffraction-grating based CPA architecture combined with large-mode-area fiber operating robustly in a single transverse mode.