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Metasurfaces composed of artificial structures have attracted a huge number of interests due to their ability on controlling the electromagnetic phase and amplitude at subwavelength scale. Beside those promising characteristics, people now intend to discover the field of meta-devices, where we can attain optical functionalities through changing the features of metasurfaces in demand. In this talk, several metasurface based components for photonic applications will be performed and discussed, including versatile polarization control, pixel-scale metalens, and achromatic meta-devices.

Metalens significantly suffers from chromatic aberration issue, which limits its applications on color images. Here we demonstrate the first broadband achromatic metalens in visible wavelength based on the concept of integrated-resonant unit elements (IRUEs).

In contrast to the traditional bulk optical elements, metasurfaces provide a new perspective on flexibly shaping the electromagnetic field by manipulating its phase, amplitude as well as polarization at will via a compact and easy-of-fabrication system. However, due to the high phase dispersion of their building blocks, metasurfaces significantly suffer from large chromatic aberration. Such chromatic aberration significantly degrades the performance of full-color optical applications, such as in communication, detection, imaging, displaying etc. Here we propose a design principle to realize achromatic metasurface devices which successfully eliminate the chromatic aberration over a continuous wavelength regions from 400 to 660 nm and 1200 to 1680 nm in a transmission and reflection scheme, respectively, for circularly-polarized incidences. For this proof-of-concept, we demonstrate broadband achromatic metalenses which are capable of focusing light with arbitrary wavelength at the same focal plane. A broadband achromatic gradient metasurface is also implemented, which is able to deflect wide-band light by the same angle. Through this approach, various flat achromatic devices that were previously impossible can be realized, which will allow innovation in full-color detection and imaging.

All forms of light manipulation depend on light–matter interaction, the fundamental mechanism is the modulation of its electromagnetic fields by the localized electromagnetic fields of atoms. The polarization of the electromagnetic field is the important factors to influence the strength of interaction. The generation and manipulation of light polarization have been traditionally accomplished with bulky optical components such as waveplates, polarizers, and polarization beam splitters that are optically thick. The miniaturization of these devices is highly desirable for the development of a new class of compact, flat, and broadband optical components that can be integrated together on a single photonics chip. Here we demonstrate a reflective metasurface polarization generator (MPG) capable of producing light beams of any polarizations all from a linearly polarized light source with a single optically thin chip. Six polarization light beams are achieved simultaneously including four linear polarizations along different directions and two circular polarizations, all conveniently separated into different reflection angles. Using the Pancharatnam– Berry phase-modulation method, the MPG sample was fabricated with aluminum as the plasmonic metal instead of the conventional gold or silver, which allowed for its broadband operation covering the entire visible spectrum. The versatility and compactness of the MPG capable of transforming any incident wave into light beams of arbitrary polarizations over a broad spectral range are an important step forward in achieving a complete set of flat optics for integrated photonics with far-reaching applications. [1]

We present the tunable optical response of phase change material Ge2Sb2Te5, which can be used to metasurfaces with varied functionalities. The concept of reconfigurable metasurface, which have different combination of unit cells with various geometries and phase states are proposed. The research is promising to apply to the area of the metadevice.

Using plasmonic nanostructures to manipulate the scattered light from the SPP waves will be experimental demonstrated. The surface plasmon waves can be scattered and modified by various plasmonic structures composed of gold nanobumps. The height and intensity profile of the focusing patterns are precisely controlled in three-dimensional space by the curved arrangement of nanobumps. The modulation of the projecting height of the focusing pattern is reached as high as 10 micron-meters. The intensity profile of focusing pattern can be approached to a diffraction-limited spot. The projecting image constructed by focusing spot from designing nanobumps arrangement is achieved in three-dimensional space.

Gold nanobumps on the thin film surface would scatter SPPs wave to forward and backward scattering light. Experiment results demonstrate 3-D forward and backward focusing are with different amplitudes and directions of the propagation waves.

We demonstrate the surface plasmonic wave on the Au thin film can be scattered and manipulated by structured Au nanobumps. Experimental results show the structured gold nanobumps can deflect the surface plasmonic waves to scattering out and focusing.

Using a femtosecond laser, the laser-direct-writing technique has been transformed into a highly efficient method that can rapidly process glass substrate into structures of Ag nanoparticles that provide plasmonic enhancement.

The femto-second-laser-treated AgO x thin film is used as the plasmon-active substrate for the applications of surface-enhanced Raman scattering (SERS), molecule sensing, and photocatalyst. The proposed technique is helpful for the solar energy harvest, green energy source, and biosensing with high efficiency and throughput.

As-deposited thin films of Ge2Sb2Te5 are investigated for the purpose of understanding the local electrical conductivity and structural phase-transitions of recorded marks under the influence of focused laser beam.

We investigate surface plasmon polariton coupling between two nano-recording marks. The different coupling characteristics and the read-out reflection signal of disk- and ring-shapes recording marks will be discussed.

The nano patterns of phase-change material Ge2Sb2Te5 are fabricated by the femto-second laser-induced forward transfer. The size and the phase state of the Ge2Sb2Te5 patterns can be effectively controlled by varying the laser fluence and film thickness. Also, the multilevel electronic states of fabricated patterns are observed through the C-AFM . This research has great potential in the area of the optical and the electrical data storage.

The optical constants including the refraction index n and extinguished coefficient k of the variety of materials are calculated from their reflection and transmittance measurements with measured wavelengths. We derive the reflectance and transmittance equations associated to the material film optical constants. The organic and inorganic materials used for optical recording medium materials are examined. The organic dyes show that significant optical constants vary with the laser wavelength, in comparison to the inorganic phase-change materials. This is an evidence to indicate the complicated bonding structure in the organic dyes within the measured wavelength ranges.