Li Cheng-Fang

Improvement of Three-Dimensional Resolution in Optical Data Storage by Combination of Two Annular Binary Phase Filters

We present an improved confocal readout system to achieve three-dimensional superresolution. This improved system is based on a combination of two different annular binary phase filters, the one designed for increasing the transverse superresolution and the other for achieving axial superresolution. By adjusting the pupil parameters, each pupil can be well designed. The simulation results show that with this improved system, the area of the central lobe of the three-dimensional point spread function of the read optics is greatly reduced. Moreover, the side-lobes are extinguished.

Design of Super-resolution Filters with a Gaussian Beam in Optical Data Storage Systems

Super-resolution filters based on a Gaussian beam are proposed to reduce the focusing spot in optical data storage systems. Both of amplitude filters and pure-phase filters are designed respectively to gain the desired intensity distributions. Their performances are analysed and compared with those based on plane wave in detail. The energy utilizations are presented. The simulation results show that our designed super-resolution filters are favourable for use in optical data storage systems in terms of performance and energy utilization.

A Novel Nano-Grating Structure of Polarizing Beam Splitters

A metal wire nanograting is fabricated and used as a polarizing beam splitter that reflects TE polarization and tramits TM polarization. The metal wire nanograting is based fully on a fully optimized design structure that consists not only of the core nanowire metal but also the substrate nanograting. The substrate nanograting is designed to provide better performance for both TM and TE polarizations. We fabricate metal-stripe gratings on a glass substrate using nanoimprint lithography and reactive ion etching process. A detailed investigation of the polarization effect 1550 nm wavelenght is carried out with the theoretical analysis and experimental results. The ploarizing beam splitter has uniform performance with wide performance with wide variations in the incident angle (+/- 25) and has high efficiency for both the reflected and the transmitted beams.

Optical realization of wavelet transform with a single lens

Two optical set-ups to implement wavelet transform with a single lens have been proposed, in which the wavelet filter was placed in front of the imaging lens or on the frequency plane. The general formula of the complex field distribution of the output plane has been deduced. The analysing wavelet functions of the band-pass wavelet filters with double and circular slits have been discussed.

Conservation Laws in sine-Gordon Equation

There are two conservation quantities needed to derive conservation laws of sine-Gordon equation in a frame of laboratory reference. One of them could be derived easily with a standard process, but the other could not. After the gauge transformation e-iθσ2/2 is introduced, we simply obtain the other one without any questionable assumption.

Theoretical investigation of negative refraction in metallic and ferromagnetic composites

A new design of LHM (left-handed material) is suggested, in which the wave vectork and the energy flowS (the Poynting vector) are in the opposite direction. Metallic cores or lines are coated with ferromagnetic layers to obtain negative permittivity and permeability. This design may bring some improvements over the binary design, such as higher homogeneity, smaller volume size, lower power loss, higher convenience and economy. The analytical expressions for the permittivity ε and permeability μ are shown to be negative in certain direction and frequency regions. Two specific structures are theoretically discussed and proved to be left-handed.

SiC-Based p+nn+ Diode for Picosecond Semiconductor Closing Switch

We study a SiC-based diode with a p+nn+ structure for picosecond semiconductor closing switch and discuss the physical process, which underlies the operation principle of high-power closing switch based on a delayed breakdown diode. By two-dimensional mixed device-circuit simulations, we demonstrate a single device reliably operated at 4 kV and at risetime 11 ps with high output dV/dt = 276 kV/ns, which is in good agreement with the experimental results.

Laser cooling using anti-stokes fluorescence in Yb3+-doped fluorozirconate glasses

The fluorozirconate glasses ZBLANP (ZrF4−BaF2−LaF3−NaF−PbF2) doped with different Yb3+ concentration were prepared. The Raman spectra and absorption spectra are measured to substantiate the existence of phonon-assisted emission. After analyzing the normalized absorption spectra of samples with different Yb3+-doped concentration, we calculated the maximum cooling effect in the 3 wt% Yb3+-doped sample pumped at 1 012.5 nm. The corresponding cooling capability is about −4.09 °C/W and the cooling efficiency reaches 1.76%.

The energy transfer in Pr3+/Yb3+ Co-doped fiber amplifier

The absorption spectrum of Pr 3+ and Pr 3+ +Yb 3+ , the fluoresce wavelength of Pr 3+ in ZBLAN glass have been measured. The energy transfer process in the Pr 3+ /Yb 3+ co\|doped fiber amplifier has been analyzed, and the probability of energy transfer between Pr 3+ and Yb 3+ has also been calculated using by electric multi\|pole interaction theory. By discussing the energy transfer rate related to the rare\|earth ion concentration and the pump wavelength, the best concentration and pump wavelength are obtained for the optimised fluores cence at 1.3 μm and the most efficent gain of fiber amplifier.