2006.4
About Instruments Today No. 151
Wideband Optical Fiber Amplifier
Extremely Broadband Semiconductor Optical Amplifiers/Tunable Semiconductor Lasers Using Nonidentical Multiple Quantum Wells [ 下載 PDF ]
Yi-Shin Su, Chi-Chia Huang, Ching-Fuh Lin
Optical fibers exhibit very low loss for the wavelength between 1300 nm and 1600 nm, so they provide a very large bandwidth for fiber-optic communications. However, the optical amplifiers or tunable lasers used in the fiber-optic communication systems have limited bandwidth. This article will introduce the use of nonidentical multiple quantum wells in a single device to achieve the purpose of very broad bandwidth. With nonidentical multiple quantum wells, the semiconductor optical amplifiers could provide nearly 300 nm of the gain bandwidth. Using such a semiconductor optical amplifier in the semiconductor-laser cavity, the semiconductor laser could have the singlewavelength operation with its wavelength tunable from 1300 nm to 1575 nm, or dual-wavelength operation with spectral spacing tunable from a few nm up to near 200 nm, or simultaneous operation at 8 wavelengths with neighboring wavelength separated for about 20 nm.
Super Wideband Chromium Doped Fiber Amplifier [ 下載 PDF ]
Kuang-Yao Huang, Jian-Cheng Chen, Chia-Yao Lo, Sheng-Lung Huang
Cr4+:YAG can generate strong infrared emission from 1.2–1.6 µm, which just covers the low-loss window of the so-called dry optical fiber. Such super wideband characteristics will facilitate the cost reduction for multi-wavelength devices as well as making them have more flexibility. In this article, we will introduce the development of super wideband optical amplifier using the double-clad Cr4+:YAG crystal fiber, which is made by a co-drawing laser heated pedestal growth method. Its material properties as well as optical gain will be characterized.
"Fiber Raman Amplifier: Principles, Structure, and Applications" [ 下載 PDF ]
Ying-Ren Chen, Jeng-Cherng Dung
In a long-haul and high-speed wavelength division multiplexing transmission system, fiber Raman amplifier distributing the gain within transmission fiber can ideally offer a better noise performance than an erbium doped fiber amplifier (EDFA), and the former allows for a much broader amplification bandwidth. The development of suitable high-power pump LDs sparked renewed interest. Researchers were quick to demonstrate some of the advantages that fiber Raman amplifier has over EDFA, particularly when the transmission fiber itself is turned into a Raman amplifier. This paper starts with the fundamental properties of stimulated Raman scattering. Then, the structure of Raman amplifier and the merits of distributing Raman gain along a transmission fiber are discussed. Finally, novel Raman pumping schemes that have recently been developed are introduced.
Principle of Broadband Erbium-Doped Fiber Amplifiers [ 下載 PDF ]
Likarn Wang
In this article, the principle of erbium-doped fiber amplifiers (EDFAs) is introduced. The physics behind optical wave amplification by an EDFA is explained with use of a generic atomic level system depicted by a set of simplified equations. The difference between the operation of a C-band EDFA and that of an L-band EDFA is described. Then, some typical C-band and L-band EDFA structures (especially the latter) and their performances are shown in this article. Finally, two broadband amplifiers both incorporating a C-band and an L-band EDFAs in the amplifying structures are briefed.
Valence State Map of Iron Oxide Thin Film Obtained from Electron Spectroscopy Imaging Series [ 下載 PDF ]
Ko-Feng Chen, Shen-Chuan Lo, Li Chang, Ji-Jung Kai, Fu-Rong Chen
A set of signal processing methods for electron spectroscopic images (ESI) series has been successfully developed for the mapping of sp2/sp3 ratio, dielectric function and energy bandgap. In this study, it was applied to the valence state map of an iron oxide thin film (Fe/α-Fe2O3). Two problems, under-sampling and a convolution effect, associated with extraction of the imagespectrum from the core loss image series were overcome by using cubic polynomial interpolation and a maximum entropy deconvolution method (MEM). The reconstructed image-spectrum obtained from the ESI series images has a quality as good as that of conventional electron energyloss spectroscopy spectra. The L3/L2 ratio of the reconstructed ESI spectrum is determined to be 3.30 ± 0.30 and 5.0 ± 0.30 for Fe and α-Fe2O3 respectively. The L3/L2 ratio mapping shows an accurate correspondence across the Cu/Fe/α-Fe2O3 area. The effect of de-localization and chromatic aberration on the resolution of ESI is discussed and is estimated to be about 2 nm for the case of L3/L2 ratio mapping. This paper demonstrates the applicability of ESI for valence state mapping of the iron-oxide system.
The Development of a Novel Electromagnetic Membrane Micropump [ 下載 PDF ]
Hung-Lin Yin, Jerwei Hsieh, Hsuan-Hsiu Hsu, Yu-Hsin Lin
Micropump is a key component in microfluidic technology. It is used to control the fluidic transportation and sequence the chemical reactions. This paper reports the development of current micropumps and introduces the basic design concepts of non-mechanical and mechanical micropumps. A novel electromagnetic membrane micropump is also proposed in this paper to provide a more effective way to control microflow. By combining this electromagnetic membrane micropump with a valve-control microfluidic chip, a portable biomedical analysis system is expected to be realized.
Introduction of Recent Advance in NMR Technology and Application [ 下載 PDF ]
Chi-Fon Chang, Fong-Ku Shi, Ying-Yann Wu
Nuclear Magnetic Resonance (NMR) is a powerful and sophisticated technique with wide range of application. During the past few years, there are witnessed significant advances in NMR hardware development as well as methods and applications. This article briefly introduce recent advance in NMR technology and application including high field magnets, shielding techniques, probe heads, analytical applications and methods in biomolecular NMR.
Electrical Impedance Tomograph — A New Medical Imaging Technique [ 下載 PDF ]
Kuo-Sheng Cheng, Yi-Yu Lu, Cheng-Yu Chen
Electrical impedance tomograph is a system that produces the electrical impedance image of the cross section of the body based on the application of current and measurement of voltage from the periphery. The impedance may be represented as two parameters such as resistivity (conductivity) and permittivity. It provides the electrical property of the tissue inside the body. The hardware design of this system includes (1) oscillator circuit, (2) current generator, (3) digital control circuit, (4) voltage measurement circuit, and (5) electrode array. The design is based on the modularized circuit, multi-current channels, and multi-frequency concept for better system testing and maintenance. The frequency for the carrier signal of proposed system may be set to be 15 kHz, 30 kHz, 80 kHz, and the combined 10 kHz and 80 kHz. The specifications of the whole system may be summarized as that it has 32 electrodes, the maximal current is ± 5 mA (rms), each current generators has 12-bit resolution in current setting, the sampling rate is 312 kHz, the input voltage range is ±4 V (rms), and the maximal load resistance is 800 Ω. The needed voltage supplies are ±12 V and 5 V. Finally, it is demonstrated to produce resistivity image for the phantom using one-step Newton-Raphson based image reconstruction algorithm.
An Introduction of Cadmium NMR Spectroscopy [ 下載 PDF ]
Lou-sing Kan, Hung-chieh Lu
The element of cadmium plays an important role in organic chemistry, inorganic chemistry, and biochemistry. The receptivity of cadmium in NMR is more superior than calcium and zinc. Thus, cadmium is also an important element for NMR other than hydrogen and carbon. In this paper, several characters of Cd NMR such as chemical shifts, Cd-H coupling constants, spin-lattice relaxation, and experimental methods were discussed via the studies of CdCl2, Cd(ClO4)2, Cd2(bis(2-pyridyl)formamidine)3, and metallo thionein. The chemical shift of Cd(ClO4)2 at the infinite dilution is recommended as the standard of Cd NMR universally.
A New Approach of Optimizing the Operation for Atomic Force Microscope in Tapping Mode (I) [ 下載 PDF ]
Ming Yen Lin, Shao Kang Hung, Chi-Yen Juan, Wei Che Liu, Yang Chih Su, Sean Ying
Tapping mode, one of the imaging methods in the atomic force microscope, has been widely used in surface measurement for decades. However, most operators who do not know the nature of the AFM may probably acquire a wrong image by try-and-error or improper setup of the AFM. In this article, according to the tip-sample interaction, a theory and method of optimizing the oscillating amplitude of the probe tip and the Set Point of the feedback system, is analytically developed from the tip sensitivity and the tip energy dissipation. A new approach of the Tapping mode, including both dynamic factors of the surface topography variation and the system feedback in scanning, is developed for the optimum criterion for AFM operation. Furthermore, the developed theory, method and rule were proved by the images scanned from four different samples. And each sample was scanned by one of four different AFMs with the process of the noise minimization and feedback gain optimization. Therefore, a theory, method and rule of optimizing the operation for AFM in tapping mode are provided and allow users to acquire images in best quality. Finally, an image with fine structures on the surface of amyloid fibrils that cause the Alzheimer's disease was first observed coincidentally during the experiments. We believe that the discovery will definitely contribute to reveal the forming process of the deposition of protein fibrils.
The Application of Photocatalytic Degradation of Organics Induced by Radio-Catalyst [ 下載 PDF ]
Ching-Tsung Yu, Tzu-Yu Chen, Ya-Ting Chang, Chu-Fang Wang
A TiO2 based photocatalytic reaction has greatly attracted many interests in environmental research. There is little literature to describe the photocatalytic reaction induced by radiation in comparison to the ultra-violet energy that can directly excite the TiO2 energy gap (3.2 eV). This paper describes the synthesis of radio-sensitive photocatalyst (BaF2/TiO2/ceramic) in which the co-existence of nanophase titania and scintillator on the ceramic powder. The photocatalyst properties were characterized by SEM, BET and ICP. Meanwhile, the results showed that photocatalytic degradation of methylene blue and resin was carried out by BaF2/TiO2/ceramic under dark condition.
