Photonic crystals have been widely studied in the fields of physics, material science and optical information technology.
In general, the standard rectangular FDTD method is used to predict the performances of photonic crystals even if it is
very time consuming and inefficient for the structures with non-orthogonal structures or inhomogeneous media. The
current authors developed a software called GCFE, which is based on non-orthogonal FDTD method .The upgraded
version of GCFE software can be used to calculate the photonic band structures, states density, transmission and
reflection coefficients of one dimensional to three dimensional photonic crystals. It has the characteristic of efficient
calculation and simple manipulation. In the present paper, the system structure of GCFE software is presented and the
implementation of the algorithm module and the result display module are described in detail. Finally the band
structures, transmission and reflection coefficients and photonic states density for the photonic crystal fibers with cube
structures are calculated by our GCFE software and the numerical application results are also shown and discussed.
Experimental results are reported on temporal instability of phase conjugate beam in a self-pumped Ce: BaTiO<sub>3</sub> phase conjugator at 532nm. The transition from stable output to unstable one is studied for various input powers, beam diameters and incident angles. Novel results that the phase conjugate output will be unsteady when control parameter <i>P<sub>S</sub></i> is within a range of 2220~3897 mW/cm<sup>2</sup> are presented. A qualitative analysis to temporal instability that instability behaviors result from competitions among the backscattering centers is given.
In this paper, the authors report their resent results of the study on the epoxy resin compound X-ray refractive lens. At the first, the theoretical results of the structure parameters for such a device are given. Then, the fabrication technologies are presented. They are deep soft X-ray lithography, mold-manufacturing and molding. The material of X-ray photoresist is PMMA, the mold is made of silicone rubber, and the material of the lens is epoxy resin. Some measured results by means of optical microscope and SEM are also shown. The structure height of the epoxy resin compound lens is measured to be 500 micrometers.
By numerical simulation, we show that the fourth-order dispersion (FOD) makes sub-picosecond optical pulse broaden as second-order dispersion (SOD), makes optical pulse oscillate simultaneously as third-order dispersion (TOD). Based on above two reasons, sub-picosecond optical pulse will be widely broaden and lead to emission of continuum radiation during propagation. Here, resemble to two- and third-order dispersion compensation, fourth-order dispersion compensation is also suggested in a dispersion-managed optical fiber link, which is realized by arranging two kinds of fiber with opposite dispersion sign in each compensation cell. For sake of avoiding excessively broadening, ultra short scale dispersion compensation cell is required in ultra high speed optical communication system. In a full dispersion compensation optical fiber system which path average dispersion is zero about SOD, TOD, and FOD, even suffering from affection of high order nonlinear like self-steep effect and self-frequency shift, 200 fs gauss optical pulse can stable propagate over 1000 km with an optimal initial chirp. When space between neighboring optical pulse is only 2 picoseconds corresponding to 500 Gbit/s transmitting capacity, eye diagram is very clarity after 1000 km. The results demonstrate that ultra short scale dispersion compensation including FOD is need and effective in ultra-high speed optical communication.
We design a kind of dual-cladding photonic crystal fiber (DC-PCF), in which air holes arranged in the vicinity of the core (inner-cladding) is smaller than the other air holes (outer-cladding). By numerical simulation, the dispersion characteristic of this novel PCF is investigated. Dispersion curves will become comparatively flat while gradually reducing the air holes arranged in inner cladding under fixing the air holes of outer cladding. An ultra-flattened dispersion can be realized when the air holes size of inner-cladding dwindling down to an optimum size. As an example, the DC-PCF demonstrates an extraordinary flattened dispersion around 9.8ps/nm.km within ±0.4ps/nm/km fluctuation range in an ultra-broad wavelength range from 1.0μm to 2.0μm . Furthermore, when the air holes arranged in the second layer nearing the core is reduced slightly, the flattened dispersion curve even can parallel shift from 11.8ps/nm/km to 7.8ps/nm/km, 6.2ps/nm/km, 4.0ps/nm/km at the wavelength around 1.55μm.
A theoretical method for evaluating the three-dimensional focusing performances of the compound x-rays lenses is presented in the present paper. The relationship between the transverse and axial focusing behaviors is considered and a simple calculation that predicts the transverse and axial focusing behaviors of the compound x-ray lenses is also presented. As an example, the three-dimensional focusing performance of a compound x-ray lens with Al material is predicted. The dependences of the three-dimensional focusing performances on the compound lenses’ structural parameters are observed for the Al compound x-ray lens. Moreover, the approximate tolerances in the setting of the receiving planes are also considered for x-rays of 4.95keV, 14.99keV and 29.78keV.
Photonic crystals have been widely studied in the fields of physics, material science and optical information technology. In general, the standard rectangular finite difference time domain (FDTD) method is used to predict the performances of photonic crystals. It is however very time consuming and inefficient. The current authors developed a software called GCFE, which is based on a non-orthogonal FDTD method. The software can be used to predict the photonic band structures, photonic states density and transmission and/or reflection coefficients for one-dimensional to three-dimensional photonic crystals. In the present paper, the derivations of the discrete Maxwell’s equations in time-domain and space-domain and the derivation of the discrete transfer matrix in real-space domain are briefly described firstly. In addition, the design idea and the functions of GCFE version 2.0.00 are introduced. Moreover, the band structures, transmission and reflection coefficients and photonic states density for the photonic crystal with cube lattice are calculated by our GCFE software, and numerical application results are also shown.
A theoretical method of focusing X-rays by the compound X-ray refractive lens is presented in this paper. The authors report their resent theoretical results including the material selection and structure parameters for such a device. As an example, a compound X-ray refractive lens with PMMA material is designed. The detailed fabrication process of the PMMA compound lens by LIGA technology is described. Moreover, some measured results by means of SEM are also shown. The structure height of one of the PMMA compound lens is measured to be 500μm.
In the present paper, a mask structure called adhering mask for excimer laser ablation is introduced. This mask is fabricated directly on the etched material, so it needn't a supporting chip and it thus has high transmission. Its absorber is made of gold and is fabricated by UV LIGA technology. Therefore the mask has more accurate structure and more smooth edges. This mask can fulfill the direct etching of the polymers by using a simpler optical system and can be a method of the mass production to some extent. The other mask is developed for X-ray lithography. It is made by UV LIGA process too. It consists of the substrate, the absorber and the supporter. The substrate is made of PI and the absorber is prepared by gold. The structure, fabrication process and experiment results of this mask are given.