In Situ Inkjet Printing Patterned Lead Halide Perovskite Quantum Dot Color Conversion Films by Using Cheap and Eco-Friendly Aqueous Inks.

Inkjet-printed perovskite quantum dot (PQD) color conversion films (CCFs) have great potentials for mini/micro-LED displays because of their ultrahigh color purity, tunable emissions, high efficiency, and high-resolution. However, current PQD inks mainly use expensive, toxic, and flammable organic substances as solvents. In this work, water is proposed to be used as the solvent for inkjet printing PQD/polymer CCFs.

Efficient light redirection via stretched field resonance in dielectric meta-resonator.

Light redirection plays an important role in photonic integrated circuit system, which attracts much attention on account of thriving application prospects from microwave to visible frequency. By treating a two-dimensional photonic crystal array as a dielectric resonator with low effective index n << 1, a new strategy of one-direction semi-enclosed meta-resonator is proposed for light redirection and splitting with a high efficiency beyond 90%. Instead of zero-index material, the phenomenon of significant collimating radiations with zero phase delay can also be achieved through a meta-resonator of low effective index to stretch the internal resonant field with a wavelength much longer than that in air.

Efficient dielectric metasurface hologram for visual-cryptographic image hiding.

Dielectric metasurfaces provide the new freedom to implement information encoding and image hiding with monolayer of artificial atoms instead of bulky optical components to enable wavelength, phase and polarization modulations. We proposed an optical encryption scheme by integrating the Visual Cyptography (VC) with the phase-encoding technique for metasurface. In the encryption process, the secret image is hidden into a group of unrecognizable and mutually-unrelated phase-only meta-holograms with high security of concealment.

Outstanding Photoluminescence in Pr-Doped Perovskite Ceramics.

Ba (ZrTi) O₃-50% (BaCa) TiO₃ (BZT-0.5BCT) ceramics with different doping contents of Pr were prepared by the conventional solid-state reaction. The phase structure and crystallinity of the fabricated ceramics were investigated by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy.

Singular value decomposition ghost imaging.

The singular value decomposition ghost imaging (SVDGI) is proposed to enhance the fidelity of computational ghost imaging (GI) by constructing a measurement matrix using singular value decomposition (SVD) transform. After SVD transform on a random matrix, the non-zero elements of singular value matrix are all made equal to 1.0, then the measurement matrix is acquired by inverse SVD transform.

Enhanced Photocatalytic Activity of Vacuum-activated TiO Induced by Oxygen Vacancies.

TiO (Degussa P25) photocatalysts harboring abundant oxygen vacancies (Vacuum P25) were manufactured using a simple and economic Vacuum deoxidation process. Control experiments showed that temperature and time of vacuum deoxidation had a significant effect on Vacuum P25 photocatalytic activity. After 240 min of visible light illumination, the optimal Vacuum P25 photocatalysts (vacuum deoxidation treated at 330 °C for 3 h) reach as high as 94% and 88% of photodegradation efficiency for rhodamine B (RhB) and tetracycline, respectively, which are around 4.

Precise displacement measurement in single-beam interferometry employing photonic metamaterial with effective zero-index.

As interferometry is the highest precision distance measuring technique, we proposed a mechanism of single-beam interferometry employing all-dielectric photonic metamaterial with effective zero-index as a means of precise displacement measurement. This mechanism offers a straightforward method for performing optical range-finding over multi-wavelength and sub-wavelength displacements in a compact uniaxial reflection configuration. The higher sensitivity and resolution can be achieved in this mechanism with the intrinsic accuracy of λ/4.

Precise identification of Dirac-like point through a finite photonic crystal square matrix.

The phenomena of the minimum transmittance spectrum or the maximum reflection spectrum located around the Dirac frequency have been observed to demonstrate the 1/L scaling law near the Dirac-like point through the finite ribbon structure. However, so far there is no effective way to identify the Dirac-like point accurately. In this work we provide an effective measurement method to identify the Dirac-like point accurately through a finite photonic crystal square matrix.

Triple-image encryption based on phase-truncated Fresnel transform and basic vector operation.

A triple-image encryption method is proposed that is based on phase-truncated Fresnel transform (PTFT), basic vector composition, and XOR operation. In the encryption process, two random phase masks, with one each placed at the input plane and the transform plane, are generated by basic vector resolution operations over the first and the second plaintext images, and then a ciphered image in the input plane is fabricated by XOR encoding for the third plaintext image. When the cryptosystem is illuminated by an on-axis plane, assisted by PTFT, the ciphered image is finally encrypted into an amplitude-only noise-like image in the output plane.

Magnetically tunable broadband transmission through a single small aperture.

Extraordinary transmission through a small aperture is of great interest. However, it faces a limitation that most of approaches can not realize the tunable transmission property, which is not benefit for the miniaturization of the microwave system. Here, we demonstrate a magnetically tunable broadband transmission through a small aperture.

Multiple-image authentication with a cascaded multilevel architecture based on amplitude field random sampling and phase information multiplexing.

A multiple-image authentication method with a cascaded multilevel architecture in the Fresnel domain is proposed, in which a synthetic encoded complex amplitude is first fabricated, and its real amplitude component is generated by iterative amplitude encoding, random sampling, and space multiplexing for the low-level certification images, while the phase component of the synthetic encoded complex amplitude is constructed by iterative phase information encoding and multiplexing for the high-level certification images. Then the synthetic encoded complex amplitude is iteratively encoded into two phase-type ciphertexts located in two different transform planes. During high-level authentication, when the two phase-type ciphertexts and the high-level decryption key are presented to the system and then the Fresnel transform is carried out, a meaningful image with good quality and a high correlation coefficient with the original certification image can be recovered in the output plane.

Negative and near zero refraction metamaterials based on permanent magnetic ferrites.

Ferrite metamaterials based on the negative permeability of ferromagnetic resonance in ferrites are of great interest. However, such metamaterials face a limitation that the ferromagnetic resonance can only take place while an external magnetic field applied. Here, we demonstrate a metamaterial based on permanent magnetic ferrite which exhibits not only negative refraction but also near zero refraction without applied magnetic field.

Zero phase delay with relax incident condition in photonic crystals.

Based on the wavefront modulation of photonic crystal (PhC), zero phase delay of propagating electromagnetic wave (EMW) can be realized with a relaxed incident condition in the PhC. The phase velocity is modulated perpendicular to the group velocity with wavefronts extending along the direction of energy flow, which lead to the phenomenon of zero phase delay with a finite spatial period. This effect can be realized simultaneously in both positive and negative refracted waves.

Optical identity authentication scheme based on elliptic curve digital signature algorithm and phase retrieval algorithm.

An optical identity authentication scheme based on the elliptic curve digital signature algorithm (ECDSA) and phase retrieval algorithm (PRA) is proposed. In this scheme, a user's certification image and the quick response code of the user identity's keyed-hash message authentication code (HMAC) with added noise, serving as the amplitude and phase restriction, respectively, are digitally encoded into two phase keys using a PRA in the Fresnel domain. During the authentication process, when the two phase keys are presented to the system and illuminated by a plane wave of correct wavelength, an output image is generated in the output plane.

An extremely broad band metamaterial absorber based on destructive interference.

We propose a design of an extremely broad frequency band absorber based on destructive interference mechanism. Metamaterial of multilayered SRRs structure is used to realize a desirable refractive index dispersion spectrum, which can induce a successive anti-reflection in a wide frequency range. The corresponding high absorptance originates from the destructive interference of two reflection waves from the two surfaces of the metamaterial.

Digital color image watermarking based on phase-shifting interferometry and neighboring pixel value subtraction algorithm in the discrete-cosine-transform domain.

A novel single-channel color-image watermarking with digital-optics means based on phase-shifting interferometry (PSI) and a neighboring pixel value subtraction algorithm in the discrete-cosine-transform (DCT) domain is proposed. The converted two-dimensional indexed image matrix from an original color image is encrypted to four interferograms by a PSI and double random-phase encoding technique. Then the interferograms are embedded in one chosen channel of an enlarged color host image in the DCT domain.

Information security system by iterative multiple-phase retrieval and pixel random permutation.

A novel information security system based on multiple-phase retrieval by an iterative Fresnel-transform algorithm and pixel random permutation (PRP) technique is proposed. In this method a series of phase masks cascaded in free space are employed and the phase distributions of all the masks are adjusted simultaneously in each iteration. It can achieve faster convergence and better quality of the recovered image compared with double-phase encoding and a similar approach in the spatial-frequency domain with the same number of phase masks and can provide a higher degree of freedom in key space with more geometric parameters as supplementary keys.