New Approach to Investigation of Tunable External Cavity Semiconductor Lasers

ＮｅｗＡｐｐｒｏａｃｈｔｏＩｎｖｅｓｔｉｇａｔｉｏｎｏｆＴｕｎａｂｌｅＥｘｔｅｒｎａｌＣａｖｉｔｙＳｅｍｉｃｏｎｄｕｃｔｏｒＬａｓｅｒｓ￥ＬＵＨｏｎｇｃｈａｎｇ；ＬＵＯＢｉｎ（ＳｏｕｔｈｗｅｓｔＪｉａｏｔｏｎｇＵｎｉｖｅｒｓｉｔｙ，Ｃｈｅｎｇｄｕ６１...     

Experimental Study on Single Frequency Semiconductor Lasers with Fiber Bragg Reflector External Cavity

ＥｘｐｅｒｉｍｅｎｔａｌＳｔｕｄｙｏｎＳｉｎｇｌｅＦｒｅｑｕｅｎｃｙＳｅｍｉｃｏｎｄｕｃｔｏｒＬａｓｅｒｓｗｉｔｈＦｉｂｅｒＢｒａｇｇＲｅｆｌｅｃｔｏｒＥｘｔｅｒｎａｌＣａｖｉｔｙ￥ＡＮＨｏｎｇｌｉｎ；ＬＩＮＸｉａｎｇｚｈｉ；ＹＡＮＨｏｎｇ；ＣＵＩＸ...     

NIR Spectroscopy and Imaging Techniques for Evaluation of Fish Quality—A Review

Abstract

Fish is a highly perishable product and it is particularly important to pay attention to its quality changes. Maintenance of the high quality of fish and fishery products necessitates development of means for precise and rapid quality evaluation. Near-infrared (NIR) spectroscopy and imaging techniques are proven technologies that can provide useful information for the estimation of quality attributes in fish and fishery products due to fast speed, noninvasiveness, ease of use, and minimal sample preparation. The aim of this review is to communicate perspectives and aspects relating to NIR spectroscopy and imaging techniques with regard to evaluation of chemical composition (fat, protein, and moisture), microbiological (freshness, spoilage, and nematodes), and sensory (flavor, texture, and color) attributes of fish and fishery products. Moreover, the usefulness of NIR spectroscopy and imaging techniques for fish authentication and classification are presented. Finally, some viewpoints on the current situation and suggestions for future research directions are proposed.     

Line-Width Reduction of a Laser Diode Array Using an External Cavity with Two Feedback Mirrors

A novel Littman-Metcalf external cavity laser diode array with two feedback mirrors is introduced. The linewidth broadening effect caused by smile can be reduced by the novel external cavity. At the drive current of 16A, the line-width is narrowed to 0.1 nm from free-running width of 1.6 nm with output efficiency of 84%.     

The Application of New Technology for Raman Spectroscopy

ＴｈｅＡｐｐｌｉｃａｔｉｏｎｏｆＮｅｗＴｅｃｈｎｏｌｏｇｙｆｏｒＲａｍａｎＳｐｅｃｔｒｏｓｃｏｐｙＹ．Ｙ．ＹａｎｇａｎｄＢ．Ｂｅｎｎｅｔｔ（Ｒｅｎｉｓｈａｗｐｌｃ．ＴｒａｎｓｄｕｃｅｒＳｙｓｔｅｍＤｉｖｉｓｉｏｎＯｌｄＴｏｗｎ，Ｗｏｔｔｏｎ－ｕｎｄｅ...     

A Step—by—Step Tunable Compound External Cavity Semiconductor Laser with Two—Side Feedback Coupling

A kind of compound external cavity semiconductor lasers(CECSL) is presented,by which laser with a discretely tunable wavelength can be obtained to meet the potential demands of the wavelength division multiplexing system.By the introduction of two-side feedback coupling in the CECSL,the CeCSL can operate more efficiently,and its side-mode suppression ratio is high up to 50dB.     

Time—dependent Theory of Raman Scattering with Pulses—Application to Continuum Raman Spectroscopy

A theory of real-time dependence of Raman scattering for a pulse-mode laser is developed within second-order perturbation theory and using the wavepacket terminology.We apply the theory to continuum Raman scattering for short and long pulses and varying pulse carrier frequency,For an initial ground virational state,it is shown that the rate of Raman emission as a funcition of time and pulse carrier frequency is structureless for all pulses,and for pulses that are longer than the dissociation time the rate also decays with the pulses.This is contrary to recently reported resonance fluorescence type structures at long times (M.Shapiro,J.Chem.Phys.99,2453(1993),We explain why such structures are unphysical for continuum Raman scattering.     

Raman Scattering of Synthetic Polymers‐A Review

Abstract

Four years after Raman discovered the Raman effect, the first spectrum of a high polymer, i.e., polystyrene, was observed by Signer and Weiler 111, so the field of Raman spectroscopy of polymers is not a new field. However, it was not until twenty years later that the second Raman spectrum of a polymer, that of poly(methy1 methacrylate), was observed [2]. The reasons for this lack of activity rest on the fact that the sample had to be clear, transparent, and nonfluorescing to obtain a Raman spectrum. Most polymers do not fall in any of these categories. Workers like Nielsen [3,4] (PE and PTFE), Tobin [5,6] (PE, PP, PTFE), Brown [7] (PE), and Tadokoro [8,9] (POM, PEG) obtained spectra with Toronto arc spectrometers out only after an enormous amount of diligent effort. However, these workers were successful in drawing attention to the potential of Raman spectroscopy as a tool for the characterization of polymers. Nielsen's review [lo] presented substantial motivation for work in this area, but the experimental difficulties tended to discourage everyone. With the advent of laser excitation and the high quality of the first reported [ll] laser Raman spectrum of a polymer, a revival of work and interest in this field ensued and many workers are now active in the field, as reflected by the increasing number of papers in Raman spectroscopy of polymers. One review of laserexcited Raman spectroscopy of polymers has already beenwritten [12].     

Raman Spectroscopy Based Techniques in Tissue Engineering—An Overview

Abstract: This article reviews the most recent applications of Raman spectroscopy (RS) in tissue engineering and regenerative medicine (TERM). Raman spectroscopy can potentially alleviate the current lack of capabilities to capture important biological data beyond the standard metabolite and pH indicators in tissue bioreactors. Key process components in bioreactors that are important to evaluate cellular integrity and functionality of tissue-engineered constructs include cells, scaffolds, and proteins. A number of studies are discussed to highlight the capability of RS in noninvasive, nondestructive, and label-free in situ analysis. Protein detection is emphasized due to the urgent need for faster and cheaper techniques. The extensiveness of protein detection studies and the inadequacy of current technology formulate the basis for detailing relevant methods seeking to improve the detection limit, specificity, or multiplexing performance of RS. We argue that RS has great promise to solve the key problem in tissue bioprocessing, namely, inadequate monitoring capabilities that handicap TERM from rising to prevalence in clinical practice.     

Optical Diagnosis for Thyroid and Parathyroid Tissues—A Review

Abstract

This article presents an overview of optical methodologies to aid the diagnosis and differentiation of thyroid and parathyroid tissues. In particular, we review the several techniques and associated methodologies that allow in vivo and ex vivo optical characterization of thyroid and parathyroid tissues. Emphasis is placed on the research potential of these techniques and whether intrinsic characteristics can provide useful contrast for the diagnosis of human thyroid and parathyroid malignant lesions.     

Modulation Frequency Multiplexed Tunable Diode Laser Spectroscopy System for Simultaneous CO, CO2 Measurements

A modulation frequency multiplexed dual diode-laser system is developed for simultaneous detection of the two most common fire gas products CO and CO2. Simultaneous detection is achieved by modulating each laser at different frequencies, demodulating the signal by a pair of lock-in amplifiers for each gas. Laser beams are combined and detected by one detector after passing through an identical optical path. The experimental results show little performance degradation associated with modulation frequency multiplexing, and no cross-talk between the two multiplexed detection channels is measured.     

A Small Signal Equivalent Circuit Model for Resonant Tunnelling Diode

We report a resonant tunnelling diode （RTD） small signal equivalent circuit model consisting of quantum capacitance and quantum inductance. The model is verified through the actual InAs/In0.53Ga0.47As/AlAs RTD fabricated on an InP substrate. Model parameters are extracted by fitting the equivalent circuit model with ac measurement data in three different regions of RTD current-voltage （I-V） characteristics. The electron lifetime, representing the average time that the carriers remain in the quasibound states during the tunnelling process, is also calculated to be 2.09ps.     

Research on Stimulated Raman Scattering Spectrum for Cavity Targets at the Shenguang-Ⅱ Laser Facility

The stimulated Raman scattering (SRS) experiments with half-cavity targets have been carried out at the Shenguang-lI laser facility. The imitative optic multiple-channel analyser (OMA) spectrograph is used to obtain the SRS experimental spectrum. We have developed a two-dimensional laser plasma interaction (LPI2D)code. The SRS spectrum for half-cavity targets is analysed theoretically and simulated numerically using the LPI2D code. These simulations quantitatively reproduce the experimental results firstly.     

A Review of “Cytogenetic Analysis for Radiation Dose Assessment—A Manual”

Abstract

Technical reports series No. 405, International Atomic Energy Agency, Vienna 2001 127 pp., 16 figures, Publication date: January 2002     

A Study of the Cis—Trans Isomers of β—Apo—12′—Carotenal By Resonance Raman Spectroscopy at Low Temperature

Resonance Raman spectroscopy is a powerful technique to study the cis-trans configurations and the intermolecular interactions of carotenoids bound to pigmentprotein complexes^[1,2].In the present invertigation,we studied a set of cis-trans isomers of β-Apo-12′－carotenal,the conjugated chain of which has a length in -between those of β-carotene and retinal,to examine whether the configurational key Raman lines which have been established for β-carotene are still valid for β-Apo-12′-caotenal^[3]     

Quantum Nonlocality in Atom—Field Coupling System via Degenerate Raman Processes with Cavity Damping

The property of quantum nonlocality in the atom-field coupling system via degenerate Raman processes with cavity damping is investigated.It is found that if the cavity dissipation is very weak,the atom-field state can exhibit quantum nonlocality periodically.The rapidity of the loss of the quantum nonlocality depends on the amplitude of the initial coherent state and the cavity damping constant.The stronger the field is and the larger the damping constant could be ,the more rapidly the nonlocality decreases.     

A Scheme for Generating Entangled Squeezed States Based on Cavity QED

We propose a scheme for generating entangled squeezed vacuum states of electromagnetical fields. The scheme is based on cavity QED. In this scheme, an atom interacts, successively, with a classical field, two quantum cavity fields, and another classical field. By detecting the final states of the atom, the two quantum cavity fields will be projected to an entangled state.     

Investigation of External Optical Feedback Resistance of IC—DFB and GC—DFB Lasers Using a Very Simple Experimental set—up

We study the external optical feedback resistance of both index-coupled(IC) and gain-coupled distributed feed-back(DFB) lasers using a very simple experimental set-up.Though IC-DFB lasers with large coupling coefficients are found to be less sensitive to external reflection,they suffer from mode instability at high injection level.On the other hand ,the introduction of gain-coupling mechanism can significantly improve both the immunity of external optical feedback and the single mode yield of the device.     

A Simple Scheme for Directly Measuring the Wigner Functions of Cavity Fields

We propose a scheme for directly measuring the Wigner functions of cavity fields.The scheme is based on the Raman interaction between atoms and cavity fields.We find a simple and direct relation between the Wigner function and the atomic population difference,By suitablychoosing the interaction time,we find that the wigner function is just two times of the atomic population difference.Thus,one can obtain the Wigner function by measuring the atomic populations and calculating the population difference.