Yongyuan Jiang

Three-dimensional hole drilling of silica glass from the rear surface with femtosecond laser pulses

By moving silica glass in a preprogrammed structure, we directly produced three-dimensional holes with femtosecond laser pulses in single step. When distilled water was introduced into a hole drilled from the rear surface of the glass, the effects of blocking and redeposition of ablated material were greatly reduced and the aspect ratio of the depth of the hole was increased. Straight holes of 4-mu;m diameter were more than 200 microm deep. Three-dimensional channels can be micromachined inside transparent materials by use of this method, as we have demonstrated by drilling a square-wave-shaped hole inside silica glass.

Holographic fabrication of multiple layers of grating inside soda–lime glass with femtosecond laser pulses

Gratings have been holographically fabricated inside soda–lime glass by two-beam interference of a single 130 fs laser pulse at a wavelength of 800 nm. Because the grating was localized in the focal volume and the depth at which the grating was formed can be controlled by translation of the sample, multiple layers of grating can be fabricated. As an example, three layers of grating have been recorded at depths of ∼200, ∼400, and ∼600 μm, respectively. These gratings can be read by either of the two recording beams with reduced energy, which demonstrates their potential applications in integrated optics and optical storage.

Wide-angle, polarization-independent and dual-band infrared perfect absorber based on L-shaped metamaterial

We propose a wide-angle, polarization-independent and dual-band infrared perfect metamaterial absorber made of double L-shaped gold patches on a dielectric spacer and opaque gold ground layer. Numerical and experimental results demonstrate that the absorber has two near-unity absorption peaks, which are result from magnetic polariton modes generated at two different resonant wavelengths. In addition, the proposed structure also shows good absorption stability in a wide range of incident anglesθfor both TE and TM incidences at azimuthal angle φ = 0°. Moreover, we demonstrate that such structure has good absorption stability for a wide range of azimuthal angles due to the excitation of perpendicular magnetic polariton modes within the asymmetric double L-shaped structure. Such structure will assist in designing magnetic polaritons absorbing element for infrared spectroscopy and imaging.

Full-color hologram using spatial multiplexing of dielectric metasurface

In this Letter, we demonstrate theoretically a full-color hologram using spatial multiplexing of dielectric metasurface for three primary colors, capable of reconstructing arbitrary RGB images. The discrete phase maps for the red, green, and blue components of the target image are extracted through a classical Gerchberg-Saxton algorithm and reside in the corresponding subcells of each pixel. Silicon nanobars supporting narrow spectral response at the wavelengths of the three primary colors are employed as the basic meta-atoms to imprint the Pancharatnam-Berry phase while maintaining minimum crosstalk between different colors. The reconstructed holographic images agree well with the target images making it promising for colorful display.

Diffusional enhancement of volume gratings as an optimized strategy for holographic memory in PQ-PMMA photopolymer

The dark enhancements of diffraction efficiency in single and multiple gratings are investigated theoretically and experimentally in phenanthrenequinone doped poly-(methyl methacrylate) materials. It is demonstrated a possibility to improve holographic characteristics of the material via the enhancement. Nearly 17-fold increment of diffraction efficiency is observed after exposure. The dependences of PQs concentration on the rate and increment of dark enhancement are achieved quantitatively. And the enhancement in multiplexing is presented as a simple and efficient method to improve response of the material and homogeneity of diffraction efficiency. PQs diffusion and enhancement process of refractive index modulation are simulated by a diffusion model for describing enhancement dynamics qualitatively and quantitatively. This study provides a significant foundation for the application of dark enhancement in holographic storage.

Fano resonance in all-dielectric binary nanodisk array realizing optical filter with efficient linewidth tuning

In this research paper, we study the Fano resonance originating from the interaction of in-phased lattice collective resonance and anti-phased lattice collective resonance supported by a binary silicon nanodisk array. Experimental results agree well with the calculations using finite-difference-time-domain method and show a strong dependence of such Fano lineshapes on the radius difference of the particles in the array. Further calculations demonstrate that such binary silicon nanodisk array can be used as an optical filter and offers an efficient way to tune the linewidth simply by changing the radius of the particles, linewidth from 12 nm to 0.7 nm and corresponding Q factor from 72 to 1290 as the radius R(2) increasing from 60 nm to 115 nm. Such scheme possessing the merits of being easily fabricated, simulated, and tuned is very promising for practical applications.

Mutual diffusion dynamics with nonlocal response in SiO 2 nanoparticles dispersed PQ-PMMA bulk photopolymer

Mutual diffusion dynamic model with nonlocal response was proposed to describe the grating formation in SiO2 nanopraticles dispersed PQ-PMMA photopolymer. The mutual-diffusion physical mechanism between PQ and SiO2 nanoparticles is analyzed. The grating formation kinetics and dynamic redistribution of components is simulated by introducing the nonlocal effect. In experiment the dark enhancement of grating after short exposure and the photopolymerization under consecutive exposure are measured. The improvement of SiO2 nanoparticles for the holographic properties is achieved quantitatively. Finally the comparison of theoretical and experimental results is presented for understanding the mutual-diffusion characteristics.

Dielectric Huygens’ Metasurface for High-Efficiency Hologram Operating in Transmission Mode

Conventional metasurface holograms relying on metal antennas for phase manipulation suffer from strong Ohmic loss and incomplete polarization conversion. The efficiency is limited to rather small values when operating in transmission mode. Here, we implement a high-efficiency transmissive metasurface hologram by leveraging the recently developed Huygens’ metasurface to construct an electric and magnetic sheet with a transmission efficiency up to 86% and optical efficiency of 23.6%. The high-efficiency originates from the simultaneous excitations of the Mie-type electric and magnetic dipole resonances in the meta-atoms composed of silicon nanodisks. Our hologram shows high fidelity over a wide spectral range and promises to be an outstanding alternative for display applications.

Apparent Negative Reflection with the Gradient Acoustic Metasurface by Integrating Supercell Periodicity into the Generalized Law of Reflection

As the two dimensional version of the functional wavefront manipulation metamaterial, metasurface has become a research hot spot for engineering the wavefront at will with a subwavelength thickness. The wave scattered by the gradient metasurface, which is composed by the periodic supercells, is governed by the generalized Snell’s law. However, the critical angle that derived from the generalized Snell’s law circles the domain of the incident angles that allow the occurrence of the anomalous reflection and refraction, and no free space scattering waves could exist when the incident angle is beyond the critical angle. Here we theoretically demonstrate that apparent negative reflection can be realized by a gradient acoustic metasurface when the incident angle is beyond the critical angle. The underlying mechanism of the apparent negative reflection is understood as the higher order diffraction arising from the interaction between the local phase modulation and the non-local effects introduced by the supercell periodicity. The apparent negative reflection phenomena has been perfectly verified by the calculated scattered acoustic waves of the reflected gradient acoustic metasurface. This work may provide new freedom in designing functional acoustic signal modulation devices, such as acoustic isolator and acoustic illusion device.

Controllable and enhanced nanojet effects excited by surface plasmon polariton

Nanojet effects excited by surface plasmon polariton at the shadow-side surfaces of dielectric microdisks positioned on gold films are reported. The surface plasmon nanojet can propagate over several optical wavelengths while still maintaining a subwavelength full-width at half-maximum transverse. Due to the nature of surface plasmon wave, the electric field of the highly confined nanojet at metal-dielectric interface is enhanced by about 30 times. By varying thickness of the dielectric microdisk, the formation of surface plasmon polariton nanojet can be flexibly controlled. The surface plasmon polariton nanojet shows great promise for enhanced Raman scattering and integrated plasmonic circuits.