In sufficiently strong scattering media, light transport is suppressed and modes are exponentially localized. Anderson-like localized states have long been recognized as potential candidates for high-${Q}$ optical modes for low-threshold, cost-effective random lasers. Operating in this regime remains, however, a challenge since Anderson localization is difficult to achieve in optics, and nonlinear

Topological insulators (TIs) implemented in synthetic dimensions have recently emerged as an attractive platform to explore higher-dimensional topological phases in compact systems. Here, we present a two-dimensional TI within a single-ring resonator enabled by acousto-optic interactions and electro-optic modulation. In our system, the synthetic dimensions are represented by the range of discrete optical

Light with orbital angular momentum (OAM) provides new insights into a wide range of physical phenomena and has engendered advanced applications in various fields. Additionally, interest in X-ray OAM has been rapidly rising. We present a straightforward method to generate intense OAM beams from an X-ray free-electron laser oscillator (XFELO). The method leverages Bragg mirrors and longitudinal-transverse

Additive color mixing modulated by digital pulses enables universal applications in lights and displays. Conventional methods map binarized signals to ordinary red–green–blue color spaces, loosely connected with the color perception of human eyes, causing the complexity of gamut mapping and inaccuracy of chromatic manipulations. Here we developed a complete theory that encodes and decodes digital signals

Nonlinear microscopy is widely used to characterize thick, optically heterogeneous biological samples. While quantitative image analysis requires accurately describing the contrast mechanisms at play, the majority of established numerical models neglect the influence of field distortion caused by sample heterogeneity near focus. In this work, we show experimentally and numerically that finite-difference

Polarization is a significant factor in a great variety of optical phenomena, playing an important role in determining the focusing properties of lenses, in the resolution of optical systems, and in the performance during laser processing. Knowing the polarization distribution in focused light is critical to understanding and designing relevant optical devices and systems. However, it remains challenging

The emerging technique of mid-infrared optical coherence tomography (MIR-OCT) takes advantage of the reduced scattering of MIR light in various materials and devices, enabling tomographic imaging at deeper penetration depths. Because of challenges in MIR detection technology, the image acquisition time is, however, significantly longer than for tomographic imaging methods in the visible/near-infrared

It has been recently demonstrated that optical pulses can hold transverse orbital angular momentum (OAM). Generation of such vortices typically requires bulky optics, and only OAMs that are fully longitudinal or transverse have been demonstrated until now. Here we investigate a general family of spatiotemporal vortices with arbitrarily oriented OAM and introduce a compact device for its generation

Unidirectionally propagated electromagnetic waves are rare in nature but heavily sought after due to their potential applications in backscatter-free optical information processing setups. It was theoretically shown that the distinct bulk optical band topologies of a gyrotropic metal and an isotropic metal can enable topologically protected unidirectional surface plasmon polaritons (SPPs) at their

Holonomies, arising from non-Abelian geometric transformations of quantum states in Hilbert space, offer a promising way for quantum computation. These holonomies are not commutable and thus can be used for the realization of a universal set of quantum logic gates, where the global geometric feature may result in some noise-resilient advantages. Here we report, to our knowledge, the first on-chip realization

We experimentally investigate the one-shot distillation of quantum coherence, which focuses on the transformations from a single copy of a given state into maximally coherent states under various incoherent operations. We present a general proposal to realize a type of strictly incoherent operations (SIOs) that can act on $N$-dimensional $(N \ge 2)$ states. This proposal is suitable for a variety of

Reliable modulation of terahertz electromagnetic waveforms is important for many applications. Here, we rapidly modulate the direction of the electric field of linearly polarized terahertz electromagnetic pulses with 1–30 THz bandwidth by applying time-dependent magnetic fields to a spintronic terahertz emitter. Polarity modulation of the terahertz field with more than 99% contrast at a rate of 10

High-intensity laser pulses covering the ultraviolet to terahertz spectral regions are nowadays routinely generated in a large number of laboratories. In contrast, intense extreme-ultraviolet (XUV) pulses have only been demonstrated using a small number of sources including free-electron laser facilities and long high-harmonic generation (HHG) beamlines. Here, we demonstrate a concept for a compact

The memorandum [Optica 7, 252 (2020). [CrossRef] ; Optica 7, 1323 (2020). [CrossRef] ] is devoted to the design, fabrication, and characterization of an optimized multi-level diffractive lens, emphasizing the advantages of the multi-level approach compared to the metalens approach. While such advantages may well exist, we feel that a number of statements in the memorandum require clarification. We

We proposed the use of relative encircled power as a measure of focusing efficiency [Optica 7, 252 (2020) [CrossRef] ]. The comment [Optica 8, 1009 (2021) [CrossRef] ] has raised useful questions, which we address briefly here and provide some clarifications.

The memorandum [Optica 7, 252 (2020). [CrossRef] ; Optica 7, 1323 (2020). [CrossRef] ] is devoted to the design, fabrication, and characterization of an optimized multi-level diffractive lens, emphasizing the advantages of the multi-level approach compared to the metalens approach. While such advantages may well exist, we feel that a number of statements in the memorandum require clarification. We

We proposed the use of relative encircled power as a measure of focusing efficiency [Optica 7, 252 (2020) [CrossRef] ]. The comment [Optica 8, 1009 (2021) [CrossRef] ] has raised useful questions, which we address briefly here and provide some clarifications.

The emerging technique of mid-infrared optical coherence tomography (MIR-OCT) takes advantage of the reduced scattering of MIR light in various materials and devices, enabling tomographic imaging at deeper penetration depths. Because of challenges in MIR detection technology, the image acquisition time is, however, significantly longer than for tomographic imaging methods in the visible/near-infrared

In recent years there has been a lot of interest in flat lenses, a category that includes diffractive lenses and metalenses. These lenses have the potential of reducing the size and cost of optical systems by replacing conventional refractive optical elements. A major obstacle to the widespread use of flat lenses is their inherent large chromatic aberration, associated with diffraction effects. To

In optically pumped lasers, heat generated by the quantum defect causes detrimental fluctuations in the output mode, frequency, and power. Common heat-mitigation techniques use bulky mechanical coolers that introduce vibrations, leading to laser frequency and amplitude noise. Here, we present a radiation-balanced fiber laser, optically cooled by anti-Stokes fluorescence (ASF). The gain medium is a

Periodically poled thin-film lithium niobate (TFLN) waveguides have emerged as a leading platform for highly efficient frequency conversion in the near-infrared. However, the commonly used silica bottom-cladding results in high absorption loss at wavelengths beyond 2.5 µm. In this work, we demonstrate efficient frequency conversion in a TFLN-on-sapphire platform, which features high transparency up

Observation of polarization modulation at the output of a submarine link, extracted from a standard coherent telecom receiver, can be used to monitor geophysical events such as sea waves and earthquakes occurring along the cable. We analyze the effect of birefringence perturbations on the polarization at the output of a long-haul submarine transmission system, and provide analytical expressions instrumental

Solitons are self-sustaining particle-like wave packets found throughout nature. Optical systems such as optical fibers and mode-locked lasers are relatively simple, are technologically important, and continue to play a major role in our understanding of the rich nonlinear dynamics of solitons. Here we present theoretical and experimental observations of a new class of optical soliton characterized

Hollow-core fibers (HCFs) are a potentially transformative fiber technology, where light is confined within a hollow core surrounded by a cladding composed of air holes defined by glass membranes. Dramatic reductions in the minimum losses achieved in a HCF are driving forward their application in low-latency data transmission and ultra-high-power delivery, and maximizing their performance is of increasing

X-ray in-line holography is well suited for three-dimensional imaging, since it covers a large field of view without the necessity of scanning. However, its resolution does not extend to the range covered by coherent diffractive imaging or ptychography. In this work, we show full-field holographic x-ray imaging based on cone-beam illumination, beyond the resolution limit given by the cone-beam numerical

Fluorescence microscopy is a powerful enabling tool for biological discovery, albeit its effective penetration depth and resolving capacity are limited due to intense light scattering in living tissues. The recently introduced short-wave infrared cameras and contrast agents featuring fluorescence emission in the second near-infrared (NIR-II) window have extended the achievable penetration to about

Lightweight and head-mountable scanning nonlinear fiberscope technologies offer an exciting opportunity for enabling mechanistic exploration of ensemble neural activities with subcellular resolution on freely behaving rodents. The tether of the fiberscope, consisting of an optical fiber and scanner drive wires, however, restricts the mouse’s movement and consequently precludes free rotation and limits

Traditional fluorescence microscopy is blind to molecular microenvironment information that is present in a fluorescence lifetime, which can be measured by fluorescence lifetime imaging microscopy (FLIM). However, most existing FLIM techniques are slow to acquire and process lifetime images, difficult to implement, and expensive. Here we present instant FLIM, an analog signal processing method that

Acousto-optic imaging (AOI) enables optical-contrast imaging deep inside scattering samples via localized ultrasound-modulation of scattered light. While AOI allows optical investigations at depths, its imaging resolution is inherently limited by the ultrasound wavelength, prohibiting microscopic investigations. Here, we propose a computational imaging approach that allows optical diffraction-limited

Supercontinuum generation and soliton microcomb formation both represent key techniques for the formation of coherent, ultrabroad optical frequency combs, enabling the RF-to-optical link. Coherent supercontinuum generation typically relies on ultrashort pulses with kilowatt peak power as a source, and so are often restricted to repetition rates less than 1 GHz. Soliton microcombs, conversely, have

Stimulated Raman scattering is an effective means of wavelength conversion and can largely extend the operating spectral range of an optical source. We demonstrate a high-performance tunable Raman laser on a sub-micrometer-thick silicon on insulator wafer using a standard foundry process. The key feature to this laser is the use of a tunable coupling mechanism to adjust both pump and signal coupling

Passively mode-locked semiconductor lasers are promising for a wide variety of chip-scale high-speed and high-capacity applications. However, the phase noise/timing jitter of such light sources are normally high, which restricts their applications. A simple and low-cost chip-scale solution to address this issue is highly desired. In this work, a two-section GaSb-based passively mode-locked laser (MLL)

Ring resonators are an interesting alternative cavity solution to the commonly used ridge-type waveguide for terahertz (THz) quantum cascade lasers. They either support a standing-wave pattern showing spatial hole burning if there are defects implemented or a traveling mode in a defect-free cavity. Here, we report on ring-shaped THz quantum cascade lasers emitting between 3.2 and 4.1 THz operating

Femtosecond power scaling in anomalous dispersion waveguides like telecom fiber is limited by runaway pulse collapse. We achieve an order of magnitude increase over previous femtosecond erbium fiber lasers by using phase-only pulse shaping in a stretcher fiber Bragg grating and identify a truncated Jacobi elliptic function pulse shape with better nonlinear compression characteristics than standard

We developed a rapid and efficient method for generating laser outputs with arbitrary shaped distributions and properties that are needed for a variety of applications. It is based on simultaneously controlling the intensity, phase, and coherence distributions of the laser. The method involves a digital degenerate cavity laser in which a phase-only spatial light modulator and spatial filters are incorporated

Unveiling the spatial and temporal dynamics of a light pulse interacting with nanosized objects is of extreme importance to widen our understanding of how photons interact with matter at the nanoscale and trigger physical and photochemical phenomena. An ideal platform to study light–matter interactions with an unprecedented spatial resolution is represented by plasmonics, which enables an extreme confinement

Integrated photonics plays a central role in modern science and technology, enabling experiments from nonlinear science to quantum information, ultraprecise measurements and sensing, and advanced applications such as data communication and signal processing. Optical materials with favorable properties are essential for nanofabrication of integrated photonics devices. Here we describe a material for

Quantum key distribution (QKD) is the best candidate for securing communications against attackers, who may in the future exploit quantum-enhanced computational powers to break classical encryption. As such, new challenges are arising from our need for large-scale deployment of QKD systems. In a realistic scenario, transmitting and receiving devices from different vendors should be able to communicate

Establishing quantum entanglement between individual nodes is crucial for building large-scale quantum networks, enabling secure quantum communications, distributed quantum computing, enhanced quantum metrology, and fundamental tests of quantum mechanics. However, the shared entanglements have been merely observed in either extremely low-temperature or well-isolated systems, which limits quantum networks

Structuring light in multiple degrees of freedom has become a powerful approach to create complex states of light for fundamental studies and applications. Here, we investigate the light field of an ultrafast laser beam with a wavelength-dependent polarization state, which we term a spectral vector beam. We present a simple technique to generate and tune such structured beams and demonstrate their

To meet the increasing needs of high-precision glass micro-optics and address the major limitations of current three-dimensional (3D) printing optics, we have developed a liquid, solvent-free, silica precursor and two-photon 3D printing process. The printed optical elements can be fully converted to transparent inorganic glass at temperatures as low as 600 C with a shrinkage rate of 17%. We have demonstrated

Strong-field ionization and Rydberg-state excitation (RSE) near the continuum threshold exhibit two phenomena that have attracted a lot of recent attention: the low-energy structure (LES) just above and frustrated tunneling ionization just below the threshold. The former becomes apparent for longer laser wavelengths, while the latter has been especially investigated in the near infrared; both have

The quarter-wavelength matching technique is widely used because it minimizes the reflection while it maximizes the transmission. The recently introduced antireflection temporal coatings (ATCs) [Optica 7, 323 (2020) [CrossRef] ] have been considered as its temporal analog. However, our study shows that by introducing an ATC, not only will the reflection be reduced but also the transmission. This phenomenon

We reply to the comment [Optica 8, 824 (2021) [CrossRef] ] on our recent article [Optica 7, 323 (2020) [CrossRef] ], where we exploited time-dependent metamaterials to achieve antireflection temporal coatings in the time domain. Clearly our approach has equivalences, but also differences, with its spatial analogue due to some fundamental differences in the physics behind temporal and spatial boundaries

This erratum corrects a typographic error that appears in Table 1 of our earlier paper [Optica 8, 539 (2021) [CrossRef] ].

We demonstrate a CMOS-foundry-based ${\rm{S}}{{\rm{i}}_3}{{\rm{N}}_4}$ photonic platform at blue and violet wavelengths that exhibits record-high intrinsic Qs of around 6 M at 453 nm and ${\lt}{{1}}\;{\rm{dB/cm}}$ waveguide propagation loss of around 405 nm.

We report a 1310 nm heterogeneous quantum-dot distributed feedback laser on silicon with high efficiency and modulation capability and demonstrate isolator-free external modulation at 25 Gb/s using a metal-oxide semiconductor capacitor microring modulator.

Conventionally, time-dependent systems add energy to electromagnetic waves by parametric amplification. Here we identify a distinct, alternative mechanism—compression of lines of force.

Silver gratings supporting surface plasmons at 532 nm catalyze the formation of light-emitting solid carbon from ${\rm CO}_2$ gas, revealing a low-energy ${\rm CO}_2$ reduction pathway involving hot electrons. Reversibility and spatial control over the formation of carbon quantum emitters are achieved.

We present a theoretical proof that the “quantum enhancement” of two-photon absorption, thought to be a means to improve molecular spectroscopy and imaging, is tightly bounded by the physics of photonic entanglement and nonlinear response.

Electro-optic modulators (EOMs) convert signals from the electrical to the optical domain. They are at the heart of optical communication, microwave signal processing, sensing, and quantum technologies. Next-generation EOMs require high-density integration, low cost, and high performance simultaneously, which are difficult to achieve with established integrated photonics platforms. Thin-film lithium

Solar sails are of great promise for space exploration, affording missions that push the limits of the possible. They enable a variety of novel science missions ranging from ultrafast interstellar travel to imaging the poles of the sun—missions that are beyond the reach of current propulsion technology. Here, we describe requirements and challenges associated with optical materials and photonic designs

Spin–orbit interaction (SOI) is a striking physical phenomenon in which spin and orbital features of a particle or a wave field affect each other. Recently, there has been significant interest in the SOI of light as it accompanies a number of fundamental light–matter interaction processes, enabling intriguing applications. We demonstrate the spin-orbit coupling between photons and phonons, in contrast

A spatiotemporal optical vortex (STOV) is an intrinsic optical orbital angular momentum (OAM) structure in which the OAM vector is orthogonal to the propagation direction [Optica 6, 1547 (2019) [CrossRef] ] and the optical phase circulates in space-time. Here, we experimentally and theoretically demonstrate the generation of the second harmonic of a STOV-carrying pulse along with the conservation of

Cell-level quantitative features of retinal ganglion cells (GCs) are potentially important biomarkers for improved diagnosis and treatment monitoring of neurodegenerative diseases such as glaucoma, Parkinson’s disease, and Alzheimer’s disease. Yet, due to limited resolution, individual GCs cannot be visualized by commonly used ophthalmic imaging systems, including optical coherence tomography (OCT)

Superresolution (SR) optical microscopy has allowed the investigation of many biological structures below the diffraction limit; however, most of the techniques are hampered by the need for fluorescent labels. Nonlinear label-free techniques such as second-harmonic generation (SHG) provide structurally specific contrast without the addition of exogenous labels, allowing observation of unperturbed biological

Volumetric interrogation of the organization and processes of intracellular organelles and molecules in cellular systems with a high spatiotemporal resolution is essential for understanding cell physiology, development, and pathology. Here, we report high-resolution Fourier light-field microscopy (HR-FLFM) for fast and volumetric live-cell imaging. HR-FLFM transforms conventional cell microscopy and

The arrayed waveguide grating (AWG) is a versatile and scalable passive photonic multiplexer that sees widespread usage. However, the necessity of a waveguide array engenders large device size, and gratings invariably commute finite power into undesired diffraction orders. Here, we demonstrate AWG-like functionality without a grating or waveguide array, yielding benefits to compactness, bandwidth,

The processing of analog microwave-frequency signals using optical means becomes increasingly important as part of advanced cellular networks. Chip-level integration of microwave photonic filters, particularly in silicon, is considered necessary for their large-scale deployment. Discrete-time, delay-and-sum filters are widely used to select narrow spectral bands out of broad optical bandwidths. However

Direct epitaxial growth of III-V light sources on Si photonic chips is promising to realize low-cost and high-functionality photonic integrated circuits. Historically, high temperature reliability of such devices has been the major roadblock due to crystalline defects from heteroepitaxy. Here, by reducing the threading dislocation densities to ${\sim}{{1}} \times {{1}}{{{0}}^6}\;{\rm{c}}{{\rm{m}}^{-