Laser printed metasurfaces: security imprints and holograms

Metasurfaces, planar metamaterials consisting of a single layer or several layers of artificial structures, not only form the basis for fundamental physics research but also have considerable technological significance. Metasurfaces can locally modify the optical property within a subwavelength range, which can facilitate device miniaturization and system integration. Metasurfaces have shown extraordinary capabilities in the local manipulation of the light's amplitude, phase, and polarization, leading to a plethora of novel applications such as generalized Snell's law of refraction and photonic spin Hall effect. This progress report is focused on the recent advancements in the fundamental research of geometric metasurfaces and their applications in ultrathin optical devices, including planar metalenses, helicity multiplexed holograms, functionality switchable devices, polarization beam splitters, vector beam generation, arbitrary polarization control, and so on. The compactness, ease of fabrication, and unusual functionalities of these devices render geometric optical metasurface devices very attractive for new applications such as encryption, imaging, anti‐counterfeiting, optical communications, quantum science, and fundamental physics. This paper aims to bring readers some new insights, and to broaden the applications of geometric metasurfaces in more research fields of science and technology.

We report an innovative detector based on subwavelength MSM photodetectors that contains no moving parts and can directly and instantaneously measure both the wavelength and polarization angle of light. The wavelength-polarization detector consists of a monolithically integrated metal-semiconductor-metal (MSM) photodetector pair with subwavelength finger spacings and widths. When the finger spacing of the MSM photodetector is smaller than the wavelength of light, the transmission of TE and TM waves through the detector fingers becomes strongly dependent on the wavelength and polarization of the incident light. As a result, the photodetector current also becomes dependent on the wavelength and polarization. However, since the photocurrent is also a function of the incident optical intensity, a pair of integrated MSM photodetectors with two different finger spacings must be used so that the photocurrent ratio will be independent of the optical power, but still be a function of the wavelength and polarization.

Information encryption and security is a prerequisite for information technology, which can be realized by an optical metasurface owing to its arbitrary manipulation over the wavelength, polarization, phase, and amplitude of light. So far information encoding can be implemented by the metasurface in one-dimensional (1D) mode (either wavelength or polarization) only with several combinations of independent channels. Herein, we design dielectric metasurfaces by multiplexing for information encoding in a two-dimensional (2D) mode of both wavelength and polarization. Sixty-three combinations made out of six independent channels by two circular polarization states (RCP and LCP) and three visible wavelengths (633, 532, and 473 nm) are experimentally demonstrated, in sharp contrast with seven combinations by three independent channels in 1D mode. This 2D mode encoding strategy enhances the encryption security dramatically and paves a novel pathway for escalating the security level of information in multichannel ...

In this article, we review recent developments in the field of surface electromagnetic wave holography. The holography principle is used as a tool to solve an inverse engineering problem consisting of designing novel plasmonic interfaces to excite either surface waves or free-space beams with any desirable field distributions. Leveraging on the new nanotechnologies to carve subwavelength features within the large diffracting apertures of conventional holograms, it is now possible to create binary holographic interfaces to shape both amplitude phase and polarization of light. The ability of the new generation of ultrathin and compact holographic optical devices to fully address light properties could find widespread applications in photonics.

Flat optical components, or metasurfaces, have transformed optical imaging, data storage, information processing, and biomedical applications by providing unprecedented control over light-matter interactions. These nano-engineered structures enable compact, multidimensional manipulation of light's amplitude, phase, polarization, and wavefront, producing scalar and vector beams with unique properties such as orbital angular momentum and knotted topologies. This flexibility has potential applications in optical communication and imaging, particularly in complex environments such as atmospheric turbulence and undersea scattering. However, designing metasurfaces for shorter wavelengths, such as visible and ultraviolet light, remains challenging due to fabrication limitations and material absorption. Here, we introduce an innovative concept called topology imprinting using judiciously designed all-dielectric nonlinear optical metasurfaces to replicate desired waveforms at fundamental and harmonic frequencies, opening promising avenues for advanced photonic applications.

The comprehensive management of light polarization states has significantly advanced various fields into a new era. With the advent of photonic integration, there has been a persistent desire to replace the bulky optical components with compact chip‐scale circuits. Nonetheless, the complete integration of polarization‐dependent systems has not yet been accomplished due to the absence of a mature polarization management scheme that possesses a tiny form factor and high foundry process compatibility meanwhile maintaining low operation complexity. Here, to overcome these limitations a novel concept called polarization phase mapping, which encodes the information between the light polarization in one waveguide and the relative light phase shift in another two waveguides, is proposed. With this bi‐directional mapping approach, the fundamental basis of polarization management has shifted from polarization adjustment to phase regulation. All essential polarization‐related functions including synthesizing, stabilizing, measuring, rotating, splitting, and mixing are demonstrated with the standard process in foundries. The size of the polarization rotating unit is pushed down to a few light wavelengths while keeping a competitive performance. Moreover, the proposed concept can be readily applied to other integrated photonics platforms. It is expected to unlock new opportunities for complex polarization‐related applications.

Fresnel zone plates consisting of multiple concentric rings have been realized by tailoring amplitude, phase and polarization of light, but conventional Fresnel zone plates require totally different materials to control each property reducing light controllability. Here, a metasurface zone plate in which rings are composed of subwavelength antenna arrays is proposed to individually control amplitude, phase and polarization by the consistent material platform of metasurfaces. Hence, versatile degrees of freedom can be achieved to focus electromagnetic waves. We verify that dielectric metasurfaces can generate arbitrary poloarization states to cover the whole Poincaré sphere in the visible regime, allowing light manipulation in the vectorial regime, which is not feasible by a conventional single liquid crystal film. Experimental demonstration of a polarization-modulated metasurface zone plate confirms the functional capability of dielectric metasurfaces exhibiting higher focusing efficiency than amplitude-modulated zone plates.

Metasurface optical holography

Metasurfaces have shown their unique capabilities to manipulate the phase and/or amplitude properties of incident light at the subwavelength scale, which provides an effective approach for constructing amplitude-only, phase-only or even complexed amplitude meta-devices with high resolution. Most of meta-devices control the amplitude and/or phase of the incident light with the same polarization state; however, separately controlling of amplitude and phase of the incident light with different polarization states can provide a new degree of freedom for improving the information capacity of metasurfaces and designing multifunctional meta-devices. Herein, we combine the amplitude manipulation and geometric phase manipulation by only reconfiguring the orientation angle of the nanostructure and present a single-sized design strategy for a multiplexing meta-hologram which plays the dual roles: a continuous amplitude-only meta-device and a two-step phase-only meta-device. Two different modulation types can be readily switched merely by polarization controls. Our approach opens up the possibilities for separately and independently controlling of amplitude and phase of light to construct a multiplexing meta-hologram with a single-sized metasurface, which can contribute to the advanced research and applications in multi-folded optical anti-counterfeiting, optical information hiding and optical information encoding.

Modelling and design of human eye inspired concentric cylindrical metalens

Metasurface is emerging as an important platform to design various functional devices due to the superior capability in controlling amplitude, phase and polarization of light through its ultrathin engineering interface. A polarized-selective hologram of all-dielectric metasurface is proposed to reconstruct multiplexed holographic images on different linear polarization status. Unlike early metasurfaces composed of plasmonic resonators with great ohmic loss at visible spectrum, the designed metasurface made of silicon nanoblocks supports a broader spectral response over the bandwidth from 600 to 760 nm with high diffraction efficiency and low crosstalk between different polarization states. Both simulation and experiment have demonstrated the feasibility and adjustability of the polarization-multiplexed metasurface hologram. We believe it will have significant technological potential in the design of optical functional devices.

Optical metasurfaces address a plethora of applications in planar optics, as they enable precise control of the phase, amplitude, and polarization of light at nanoscale interaction lengths. However, their implementation requires surface nanostructuring, based on complex design and fabrication methods. In addition, exploiting narrow spectral features, e.g., for sensing, is accompanied by high demands in terms of precise post‐process alignments of probing light—impractical for compact optical systems. Here, the realization of plasmonic metasurfaces, based on silver nanoparticles (AgNPs) and using a solution‐based growth method, is demonstrated. The particle growth is mediated by localized surface plasmon resonances. The resulting nanostructures are directly applicable as self‐optimized metasurfaces in optical systems, as their fabrication and probing procedures allow the use of common—photonic and plasmonic—platforms. Information regarding the electromagnetic (EM) environment is stored during the fabrication via distinct particle positions and dimensions. The resulting optical response is inherently sensitive to deviations from this EM environment—enabling high‐performance nanoplasmonic sensing with a maximum discrete Figure of Merit* ( of 968 without the need for post‐process alignments.

Spatial light modulators (SLMs), which control the amplitude, phase, and polarization of light are the core components of many optical applications. Integrating graphene with dielectric metasurfaces supporting quasi-bound states in the continuum (quasi-BIC) offers potential advantages of low energy consumption, high speed, and small size of modulators. In this paper, we propose a modulator with a 2π phase shift, by transforming the coupled system from an underdamped resonator to an overdamped one by tuning the Fermi level of graphene through simulation. Additionally, we demonstrate the application of this device in one-bit programmed holography. The proposed modulator with its combined advantages of low power consumption and compact footprint, enables fruitful applications in holographic display, beam steering in light detection, ranging and biomedical imaging systems.

Optical metasurfaces offer innovative approaches to manipulate the amplitude, phase, frequency, and polarization of light in localized regions, thus paving the way for a viable technology that can be applied in various domains, including structural coloration, multiplexed holography, and high‐resolution displays. To address the escalating need for sophisticated encryption, a novel quadruple‐security flexible plasmonic anti‐counterfeiting platform is proposed that utilizes printable centimeter‐scale (0.6 cm) metasurfaces. These metasurfaces feature four distinct signatures: They appear as color images under ambient incoherent white light, while projecting up to three different holograms under red, green, or blue circularly polarized laser illumination. Such holographic color nanoprintings are not only easily authenticated but also difficult to imitate, offering enhanced security in anti‐counterfeiting applications. The design of these multifunctional metasurfaces, which encode information solely in the surface relief of a single polymeric material with a silver coating, allows for efficient mass production through UV nanoimprinting lithography. Given the superior performance of these multifunctional plasmonic metasurfaces, this work presents tremendous potential in various fields such as multi‐level information security, cost‐effective anti‐counterfeiting, and many others.

Mueller–Stokes polarimetry is emerging as a prominent noninvasive imaging technique to study the structural characteristics of an anisotropic medium. Spatial light modulator (SLM) is a programmable liquid crystal device (LCD), which is used to modulate the amplitude, phase, and polarization of light. The compact design and cumbrous manufacturing process of SLM requires its polarimetric calibration prior to its utilization for various applications. In this study, we experimentally demonstrate Mueller–Stokes imaging of a reflective-type SLM (Holoeye, LCR-720) to calibrate its polarization modulation characteristics with respect to its dynamic gray value range (0–255) at different spatial locations of SLM screen. Mueller matrices at 18 different gray values of SLM at an interval of 15, that is, at gray values 0, 15, 30, up to 255 have been experimentally measured using an improvised Mueller matrix imaging polarimeter (MMIP). Crucial polarimetric characteristics, that is, diattenuation, polarizance, state of polarization (SOP), depolarization, and retardance have been estimated with respect to the gray value range of SLM. Significant polarization modulation characteristics [diattenuation (0.08–0.3), polarizance (0.02–0.2), and retardance (0 to π)] have been determined for the SLM. These results indicate that the SLM exhibits spatially variable depolarizing nature and hence it is not perfectly homogeneous in structure. Therefore, it is expected that the outcomes of this study would be helpful for exploring the applicability of Mueller–Stokes polarimetry in advancement of LC technology.