Yuan Hsing Fu

Metamaterial with polarization and direction insensitive resonant transmission response mimicking electromagnetically induced transparency

We report on a planar metamaterial, the resonant transmission frequency of which does not depend on the polarization and angle of incidence of electromagnetic waves. The resonance results from the excitation of high-Q antisymmetric trapped current mode and shows sharp phase dispersion characteristic to Fano-type resonances of the electromagnetically induced transparency phenomenon.

Pure angular momentum generator using a ring resonator

This paper reports a pure angular momentum generator using a ring resonator surrounded by a group of nano-rods. The evanescent waves of the circulating light in the ring are scattered by the nano-rods and generate a rotating electromagnetic field, which has only angular momentum but no linear momentum along the axis of rotation. The angular order is determined by the difference between the order of Whispering Gallery mode and the number of the rods, the rotating frequency is equal to the light frequency divided by the angular order. The maximum amplitude of the rotating electromagnetic fields can be 10 times higher than the amplitude of the input field when there are 36 rods (R(rod) = 120 nm, nr = 1.6). The pure angular momentum generator provides a new platform for trapping and rotation of small particles.

Tuneable electron-beam-driven nanoscale light source

Recently demonstrated ‘light-wells’—free-electron-driven tuneable nanoscale light sources—generate optical photons as electrons travel down a nano-hole through a metal‐dielectric multilayer structure. We report here on the application of boundary element modeling methods to the simulation of light-well output characteristics. The model is found to successfully reproduce the key features observed in experiment and as such will aid in the development and optimization of future device structures.

Study of the optical response of phase-change recording layer with zinc oxide nanostructured thin film.

Recently, use of nanostructured materials as a near‐field optical active layer has attracted a lot of interest. The non‐linear optical properties and strong enhancements of metallic oxide nanostructured thin films are key functions in applications of promising nanophotonics. For the importance of ultra‐high density optical data storage, we continue investigating the ultra‐high density recording property of near‐field optical disk consisting of zinc oxide (ZnOx) nanostructured thin film. A carrier‐to‐noise ratio above 38 dB at a recording mark size of 100 nm can be obtained in the ZnOx near‐field optical disk by a DVD driver tester directly. In this article, we use an optical pump‐probe system (static media tester) to measure the optical response of a phase‐change recording layer (Ge2Sb2Te5) and demonstrate the high contrast of optical recording with a ZnOx nanostructured thin film in short pulse durations. Also, we investigate the dependence of writing power and the optical response in conventional re‐writable recording layers and the phase‐change material with ZnOx nanostructured thin film.

Imaging of Recording Marks and Their Jitters With Different Writing Strategy and Terminal Resistance of Optical Output

The relation between recording mark formation and jitter value with radial orient spot (ROS) type laser spot recording was investigated by using a new imaging method of conductive-atomic force microscopy (C-AFM). The readout performances of recording marks were studied by changing the terminal resistance of optical pickup head and writing strategies. The results of clear C-AFM images showed that is possible to adjust the conditions of terminal resistance and writing strategies to have better readout signal performance.

Z-Scan Study of Nonlinear Optical Coupling of PtOx and Ge2Sb2Te5 of Near-Field Optical Recording Structure

The strong local nonlinear optical coupling properties of a 5 nm PtOx thin film sandwiched by two Ge2Sb2Te5 phase-change structures of a new type super-resolution near-field optical disk are investigated and observed by Z-scan experiments.

Implementation of a short-tip tapping-mode tuning fork near-field scanning optical microscope

We present the implementation of a short‐tip tapping‐mode tuning fork near‐field scanning optical microscope. Tapping frequency dependences of the piezoelectric signal amplitudes for a bare tuning fork fixed on the ceramic plate, a short‐tip tapping‐mode tuning fork scheme and an ordinary tapping‐mode tuning fork configuration with an 80‐cm optical fibre attached are demonstrated and compared. Our experimental results show that this new short‐tip tapping‐mode tuning fork scheme provides a stable and high Q factor at the tapping frequency of the tuning fork and will be very helpful when long optical fibre probes have to be used in an experiment. Both collection and excitation modes of short‐tip tapping‐mode tuning fork near‐field scanning optical microscope are applied to study the near‐field optical properties of a single‐mode telecommunication optical fibre and a green InGaN/GaN multiquantum well light‐emitting diode.

Calculation of Surface Plasmon Effect on Optical Discs

We calculated the conditions of surface plasmon resonance for various optical discs to evaluate the role of periodic lands and grooves or recording mark trains as grating couplers. With the typical parameters of structure used in the discs, it is shown that surface plasmons have a weak influence on ordinary optical discs. These results differ from the situation with super-resolution near-field optical structures where surface plasmons or localized surface plasmons have a considerable influence on such discs.

Nonlinear optical properties of the Au-SiO2 nanocomposite superresolution near-field thin film

A Au-SiO2 superresolution nanocomposite active nonlinear optical thin film is fabricated reproducibly by cosputtering method with the size of Au nano particles around 2 to 10 nm. Results of the Z-scan indicate that these nanocomposite Au-SiO2 films have nonlinear optical properties and enhanced transmittance at the focusing position. For a 15-nm-thick Au-SiO2 nanocomposite thin film, the transmittance can be 135% for a sample with an average grain size of around 5 nm.

Study of the focused laser spots generated by various polarized laser beam conditions

In this work, three‐dimensional near‐field imaging of the focused laser spot was studied theoretically and experimentally. In the theoretical simulation, we use the electromagnetic equivalent of the vectorial Kirchhoff diffraction integral to calculate the intensity distribution of the focal region, and a high depolarization is found in high numerical aperture systems (NA = 0.85). The experimental set‐up is based on a near‐field scanning optical microscope (NSOM) system. A high‐NA objective lens is used to focus incident light of various polarizations, and a tapered near‐field optical fibre probe of the NSOM system is used to determine the intensity of the focal field. The results show an asymmetric distribution of the focused intensity with the linear polarized laser beam.