In recent years, notable progress has been achieved in both the hardware and algorithms of structured illumination microscopy (SIM). Nevertheless, the advancement of three-dimensional structured illumination microscopy (3DSIM) has been impeded by challenges arising from the speed and intricacy of polarization modulation. We introduce a high-speed modulation 3DSIM system, leveraging the polarization-maintaining and modulation capabilities of a digital micromirror device (DMD) in conjunction with an electro-optic modulator. The DMD-3DSIM system yields a twofold enhancement in both lateral (133 nm) and axial (300 nm) resolution compared to wide-field imaging and can acquire a data set comprising 29 sections of 1024 pixels×1024 pixels, with 15 ms exposure time and 6.75 s per volume. The versatility of the DMD-3DSIM approach was exemplified through the imaging of various specimens, including fluorescent beads, nuclear pores, microtubules, actin filaments, and mitochondria within cells, as well as plant and animal tissues. Notably, polarized 3DSIM elucidated the orientation of actin filaments. Furthermore, the implementation of diverse deconvolution algorithms further enhances 3D resolution. The DMD-based 3DSIM system presents a rapid and reliable methodology for investigating biomedical phenomena, boasting capabilities encompassing 3D superresolution, fast temporal resolution, and polarization imaging.

Spatiotemporal shaping of ultrashort pulses is pivotal for various technologies, such as burst laser ablation and ultrafast imaging. However, the difficulty of pulse stretching to subnanosecond intervals and independent control of the spatial profile for each pulse limit their advancement. We present a pulse manipulation technique for producing spectrally separated GHz burst pulses from a single ultrashort pulse, where each pulse is spatially shapable. We demonstrated the production of pulse trains at intervals of 0.1 to 3 ns in the 800- and 400-nm wavelength bands and applied them to ultrafast single-shot transmission spectroscopic imaging (4 Gfps) of laser ablation dynamics with two-color sequentially timed all-optical mapping photography. Furthermore, we demonstrated the production of pulse trains containing a shifted or dual-peak pulse as examples of individual spatial shaping of GHz burst pulses. Our proposed technique brings unprecedented spatiotemporal manipulation of GHz burst pulses, which can be useful for a wide range of laser applications.

Chaotic optical communication has shown large potential as a hardware encryption method in the physical layer. As an important figure of merit, the bit rate–distance product of chaotic optical communication has been continually improved to 30 Gb/s × 340 km, but it is still far from the requirement for a deployed optical fiber communication system, which is beyond 100 Gb/s × 1000 km. A chaotic carrier can be considered as an analog signal and suffers from fiber channel impairments, limiting the transmission distance of high-speed chaotic optical communications. To break the limit, we propose and experimentally demonstrate a pilot-based digital signal processing scheme for coherent chaotic optical communication combined with deep-learning-based chaotic synchronization. Both transmission impairment recovery and chaotic synchronization are realized in the digital domain. The frequency offset of the lasers is accurately estimated and compensated by determining the location of the pilot tone in the frequency domain, and the equalization and phase noise compensation are jointly performed by the least mean square algorithm through the time domain pilot symbols. Using the proposed method, 100 Gb/s chaotically encrypted quadrature phase-shift keying (QPSK) signal over 800 km single-mode fiber (SMF) transmission is experimentally demonstrated. In order to enhance security, 40 Gb/s real-time chaotically encrypted QPSK signal over 800 km SMF transmission is realized by inserting pilot symbols and tone in a field-programmable gate array. This method provides a feasible approach to promote the practical application of chaotic optical communications and guarantees the high security of chaotic encryption.

Orbital angular momentum (OAM), described by an azimuthal phase term exp ( jlθ ) , has unbound orthogonal states with different topological charges l. Therefore, with the explosive growth of global communication capacity, especially for short-distance optical interconnects, light-carrying OAM has proved its great potential to improve transmission capacity and spectral efficiency in the space-division multiplexing system due to its orthogonality, security, and compatibility with other techniques. Meanwhile, 100-m free-space optical interconnects become an alternative solution for the “last mile” problem and provide interbuilding communication. We experimentally demonstrate a 260-m secure optical interconnect using OAM multiplexing and 16-ary quadrature amplitude modulation (16-QAM) signals. We study the beam wandering, power fluctuation, channel cross talk, bit-error-rate performance, and link security. Additionally, we also investigate the link performance for 1-to-9 multicasting at the range of 260 m. Considering that the power distribution may be affected by atmospheric turbulence, we introduce an offline feedback process to make it flexibly controllable.

The use of orbital angular momentum (OAM) as an independent dimension for information encryption has garnered considerable attention. However, the multiplexing capacity of OAM is limited, and there is a need for additional dimensions to enhance storage capabilities. We propose and implement orbital angular momentum lattice (OAML) multiplexed holography. The vortex lattice (VL) beam comprises three adjustable parameters: the rotation angle of the VL, the angle between the wave normal and the z axis, which determines the VL’s dimensions, and the topological charge. Both the rotation angle and the VL’s dimensions serve as supplementary encrypted dimensions, contributing azimuthally and radially, respectively. We investigate the mode selectivity of OAML and focus on the aforementioned parameters. Through experimental validation, we demonstrate the practical feasibility of OAML multiplexed holography across multiple dimensions. This groundbreaking development reveals new possibilities for the advancement of practical information encryption systems.

Mode-division multiplexers (MDMUXs) play a pivotal role in enabling the manipulation of an arbitrary optical state within few-mode fibers, offering extensive utility in the fields of mode-division multiplexing and structured optical field engineering. The exploration of MDMUXs employing cascaded resonant couplers has garnered significant attention owing to their scalability, exceptional integration capabilities, and the anticipated low insertion loss. In this work, we present the successful realization of high-quality orbital angular momentum MDMUX corresponding to topological charges 0, ±1, and ±2, achieved through the utilization of cascaded fused-biconical tapered couplers. Notably, the measured insertion losses at 1550 nm exhibit remarkable minimal values: 0.31, 0.10, and 0.64 dB, respectively. Furthermore, the 80% efficiency bandwidths exceed 106, 174, and 174 nm for these respective modes. The MDMUX is composed of precision-manufactured high-quality mode selective couplers (MSCs). Utilizing a proposed supermode propagation method based on mode composition analysis, we precisely describe the operational characteristics of MSCs. Building upon this comprehensive understanding, we embark on a pioneering analysis elucidating the influence of MSC cascading order on the performance of MDMUXs. Our theoretical investigation substantiates that when constructing MDMUXs, MSCs should adhere to a specific cascading sequence.

Carbon-based materials, such as graphene and carbon nanotubes, have emerged as a transformative class of building blocks for state-of-the-art metamaterial devices due to their excellent flexibility, light weight, and tunability. In this work, a tunable carbon-based metal-free terahertz (THz) metasurface with ultrabroadband absorption is proposed, composed of alternating graphite and graphene patterns, where the Fermi level of graphene is adjusted by varying the applied voltage bias to achieve the tunable ultrabroadband absorption characteristics. In particular, when the Fermi level of graphene is 1 eV, the absorption coefficient exceeds 90% from 7.24 through 16.23 THz, and importantly, the absorption bandwidth reaches as much as 8.99 THz. In addition, it is polarization-insensitive to incident waves and maintains a high absorption rate at an incident angle of up to 50 deg. This carbon-based device enjoys higher absorption bandwidth, rates, and performance compared to conventional absorbers in the THz regime and can be potentially applied in various fields, including THz wave sensing, modulation, as well as wearable health care devices, and biomedicine detection.

A supercontinuum white laser with ultrabroad bandwidth, intense pulse energy, and high spectral flatness can be accomplished via synergic action of third-order nonlinearity (3rd-NL) and second-order nonlinearity. In this work, we employ an intense Ti:sapphire femtosecond laser with a pulse duration of 50 fs and pulse energy up to 4 mJ to ignite the supercontinuum white laser. Remarkably, we use water instead of the usual solid materials as the 3rd-NL medium exhibiting both strong self-phase modulation and stimulated Raman scattering effect to create a supercontinuum laser with significantly broadened bandwidth and avoid laser damage and destruction. Then the supercontinuum laser is injected into a water-embedded chirped periodically poled lithium niobate crystal that enables broadband and high-efficiency second-harmonic generation. The output white laser has a 10 dB bandwidth encompassing 413 to 907 nm, more than one octave, and a pulse energy of 0.6 mJ. This methodology would open up an efficient route to creating a long-lived, high-stability, and inexpensive white laser with intense pulse energy, high spectral flatness, and ultrabroad bandwidth for application to various areas of basic science and high technology.

Unlike conventional topological edge states confined at a domain wall between two topologically distinct media, the recently proposed large-area topological waveguide states in three-layer heterostructures, which consist of a domain featuring Dirac points sandwiched between two domains of different topologies, have introduced the mode width degree of freedom for more flexible manipulation of electromagnetic waves. Until now, the experimental realizations of photonic large-area topological waveguide states have been exclusively based on quantum Hall and quantum valley-Hall systems. We propose a new way to create large-area topological waveguide states based on the photonic quantum spin-Hall system and observe their unique feature of pseudo-spin-momentum-locking unidirectional propagation for the first time in experiments. Moreover, due to the new effect provided by the mode width degree of freedom, the propagation of these large-area quantum spin-Hall waveguide states exhibits unusually strong robustness against defects, e.g., large voids with size reaching several unit cells, which has not been reported previously. Finally, practical applications, such as topological channel intersection and topological energy concentrator, are further demonstrated based on these novel states. Our work not only completes the last member of such states in the photonic quantum Hall, quantum valley-Hall, and quantum spin-Hall family, but also provides further opportunities for high-capacity energy transport with tunable mode width and exceptional robustness in integrated photonic devices and on-chip communications.

As an optical processor, a diffractive deep neural network (D2NN) utilizes engineered diffractive surfaces designed through machine learning to perform all-optical information processing, completing its tasks at the speed of light propagation through thin optical layers. With sufficient degrees of freedom, D2NNs can perform arbitrary complex-valued linear transformations using spatially coherent light. Similarly, D2NNs can also perform arbitrary linear intensity transformations with spatially incoherent illumination; however, under spatially incoherent light, these transformations are nonnegative, acting on diffraction-limited optical intensity patterns at the input field of view. Here, we expand the use of spatially incoherent D2NNs to complex-valued information processing for executing arbitrary complex-valued linear transformations using spatially incoherent light. Through simulations, we show that as the number of optimized diffractive features increases beyond a threshold dictated by the multiplication of the input and output space-bandwidth products, a spatially incoherent diffractive visual processor can approximate any complex-valued linear transformation and be used for all-optical image encryption using incoherent illumination. The findings are important for the all-optical processing of information under natural light using various forms of diffractive surface-based optical processors.

Quantum technologies rely on creating and manipulating entangled sources, which are essential for quantum information, communication, and imaging. By integrating quantum technologies and all-dielectric metasurfaces, the performance of miniature display devices can be enhanced to a higher level. Miniature display technology, such as virtual reality display, has achieved original commercial success, and was initially applied to immersive games and interactive scenes. While the consumer market has quickly adopted this technology, several areas remain for improvement, including concerns around bulkiness, dual-channel display, and noise reduction. Here, we experimentally realize a quantum meta-hologram concept demonstration of a miniature display. We fabricate an ultracompact meta-hologram based on 1 μm thick titanium dioxide (TiO2). The meta-hologram can be remotely switched with heralding technique and is robust against noise with the quantum entangled source. The platform can alter the miniature display channel by manipulating heralding photons’ polarization, removing speckles and multiple reflective light noise, improving imaging contrast, and potentially decreasing device weight. Imaging contrast increases from 0.36 dB under speckle noise influences to 6.8 dB in quantum correlation imaging. This approach has the potential to miniaturize quantum displays and quantum communication devices.

This study introduces a handheld terahertz (THz) scanner designed to quantitatively evaluate human skin hydration levels and thickness. This device, through the incorporation of force sensors, demonstrates enhanced repeatability and accuracy over traditional fixed THz systems. The scanner was evaluated in the largest THz skin study to date, assessing 314 volunteers, successfully differentiating between individuals with dry skin and hydrated skin using a numerical stratified skin model. The scanner measures and displays skin hydration dynamics within a quarter of a second, indicating its potential for real-time, noninvasive examinations, opening up opportunities for in vivo and ex vivo diagnosis during patient consultations. Furthermore, the portability and ease of use of our scanner enable its widespread application for in vivo and ex vivo diagnosis during patient consultations, potentially allowing in situ biopsy evaluation and elimination of histopathology processing wait times, thereby improving patient outcomes by facilitating simultaneous tumor diagnosis and removal.

We present a unified electromagnetic modeling of coherence scanning interferometry, confocal microscopy, and focus variation microscopy as the most common techniques for surface topography inspection with micro- and nanometer resolution. The model aims at analyzing the instrument response and predicting systematic deviations. Since the main focus lies on the modeling of the microscopes, the light–surface interaction is considered, based on the Kirchhoff approximation extended to vectorial imaging theory. However, it can be replaced by rigorous methods without changing the microscope model. We demonstrate that all of the measuring instruments mentioned above can be modeled using the same theory with some adaption to the respective instrument. For validation, simulated results are confirmed by comparison with measurement results.

The article provides information about the image on the cover of Advanced Photonics Nexus, Volume 3, Issue 1.