oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Tuning Semiconductor Laser Diode Lasing Frequency and Narrowing the Laser Linewidth Using External Oscillating Driving Field  [PDF]
H.S. Ashour
Journal of Applied Sciences , 2006,
Abstract: In this study, we propose a new method to tune the semiconductor laser lasing frequency and reducing the laser linewidth using an external deriving field. We redeveloped Floquet S-matrix which determines the transmission probabilities and the shape and position of the induced quasibound state, which accumulated incident electrons. We explored the S-matrix numerically for various system parameters. We found that the oscillating field amplitude V1 plays a curial rule in defining the profile of electrons accumulations in the quasibound state and the field`s strength made sift the position of the quasibound state. This sift in the bound state energy due field`s strength is used to tune the lasing frequency and the output of the semiconductor laser linewidth is improved by changing the field`s amplitude the deriving field. By narrowing down the electron accumulations profile the laser linewidth would be narrower.
Control of lasing in fully chaotic open microcavities by tailoring the shape factor  [PDF]
W. Fang,G. S. Solomon,H. Cao
Physics , 2006, DOI: 10.1063/1.2535692
Abstract: We demonstrate experimentally that lasing in a semiconductor microstadium can be optimized by controlling its shape. Under spatially uniform optical pumping, the first lasing mode in a GaAs microstadium with large major-to-minor-axis ratio usually corresponds to a high-quality scar mode consisting of several unstable periodic orbits. Interference of waves propagating along the constituent orbits may minimize light leakage at particular major-to-minor-axis ratio. By making stadium of the optimum shape, we are able to maximize the mode quality factor and align the mode frequency to the peak of the gain spectrum, thus minimizing the lasing threshold. This work opens the door to control chaotic microcavity lasers by tailoring the shape factor.
Synchronization in semiconductor laser rings  [PDF]
Javier M. Buldu,M. C. Torrent,Jordi Garcia-Ojalvo
Physics , 2006, DOI: 10.1109/JLT.2007.895555
Abstract: We examine the dynamics of semiconductor lasers coupled in a ring configuration. The lasers, which have stable output intensity when isolated, behave chaotically when coupled unidirectionally in a closed chain. In this way, we show that neither feedback nor bidirectional coupling is necessary to induce chaotic dynamics at the laser output. We study the synchronization phenomena arising in this particular coupling architecture, and discuss its possible application to chaos-based communications. Next, we extend the study to bidirectional coupling and propose an appropriate technique to optical chaos encryption/decryption in closed chains of mutually coupled semiconductor lasers.
Octave-spanning semiconductor laser  [PDF]
Markus R?sch,Giacomo Scalari,Mattias Beck,Jér?me Faist
Physics , 2014, DOI: 10.1038/nphoton.2014.279
Abstract: We present here a semiconductor injection laser operating in continuous wave with an emission covering more than one octave in frequency, and displaying homogeneous power distribution among the lasing modes. The gain medium is based on a heterogeneous quantum cascade structure operating in the THz range. Laser emission in continuous wave takes place from 1.64 THz to 3.35 THz with optical powers in the mW range and more than 80 modes above threshold. Free-running beatnote investigations on narrow waveguides with linewidths of 980 Hz limited by jitter indicate frequency comb operation on a spectral bandwidth as wide as 624 GHz, making such devices ideal candidates for octave-spanning semiconductor-laser-based THz frequency combs.
Wide and Fast Wavelength-Swept Fiber Laser Based on Dispersion Tuning for Dynamic Sensing  [PDF]
Shinji Yamashita,Yuichi Nakazaki,Ryosei Konishi,Osamu Kusakari
Journal of Sensors , 2009, DOI: 10.1155/2009/572835
Abstract: We have developed a unique wide and fast wavelength-swept fiber laser for dynamic and accurate fiber sensing. The wavelength tuning is based on the dispersion tuning technique, which simply modulates the loss/gain in the dispersive laser cavity. By using wideband semiconductor optical amplifiers (SOAs), the sweep range could be as wide as ~180 nm. Since the cavity contains no mechanical components, such as tunable filters, we could achieve very high sweep rate, as high as ~200 kHz. We have realized the swept lasers at three wavelength bands, 1550 nm, 1300 nm, and 800 nm, using SOAs along with erbium-doped fiber amplifiers (EDFAs), and in two laser configurations, ring and linear ones. We also succeeded in applying the swept laser for a dynamic fiber-Bragg grating (FBG) sensor system. In this paper, we review our researches on the wide and fast wavelength-swept fiber lasers.
Monolithic integration of widely tunable sampled grating DBR laser with tilted semiconductor optical amplifier
单片集成倾斜SOA的宽可调谐取样光栅分布布拉格反射激光器

Liu Yang,Ye Nan,Wang Baojun,Zhou Daibing,An Xin,Bian Jing,Pan Jiaoqing,Zhao Lingjuan,Wang Wei,
刘扬
,叶楠,王宝军,周代兵,安欣,边静,潘教青,赵玲娟,王圩

半导体学报 , 2010,
Abstract: High output powers and wide range tuning have been achieved in a sampled grating distributed Bragg reflector laser with an integrated semiconductor optical amplifier. Tilted amplifier and anti-reflection facet coating are used to suppress reflection. We have demonstrated sampled grating DBR laser with a tuning range over 38 nm, good wavelength coverage and peak output powers of more than 9 mW for all wavelengths.
High-Power Hybrid Mode-Locked External Cavity Semiconductor Laser Using Tapered Amplifier with Large Tunability  [PDF]
Andreas Schmitt-Sody,Andreas Velten,Ye Liu,Ladan Arissian,Jean-Claude Diels
International Journal of Optics , 2008, DOI: 10.1155/2008/865092
Abstract: We report on hybrid mode-locked laser operation of a tapered semiconductor amplifier in an external ring cavity, generating pulses as short as 0.5 ps at 88.1 MHz with an average power of 60 mW. The mode locking is achieved through a combination of a multiple quantum well saturable absorber (>10% modulation depth) and an RF current modulation. This designed laser has 20 nm tuning bandwidth in continuous wave and 10 nm tuning bandwidth in mode locking around 786 nm center wavelength at constant temperature.
Quantum shape effects on Zeeman splittings in semiconductor nanostructures  [PDF]
Pochung Chen
Physics , 2005, DOI: 10.1103/PhysRevB.72.045335
Abstract: We develop a general method to calculate Zeeman splittings of electrons and holes in semiconductor nanostructures within the tight-binding framework. The calculation is carried out in the electron-hole picture and is extensible to the excitonic calculation by including the electron-hole Coulomb interaction. The method is suitable for the investigation of quantum shape effects and the anisotropy of the g-factors. Numerical results for CdSe and CdTe nanostructures are presented.
Continuous Spatial Tuning of Laser Emissions in a Full Visible Spectral Range  [PDF]
Mi-Yun Jeong,Jeong Weon Wu
International Journal of Molecular Sciences , 2011, DOI: 10.3390/ijms12032007
Abstract: In order to achieve a continuous tuning of laser emission, the authors designed and fabricated three types of cholesteric liquid crystal cells with pitch gradient, a wedge cell with positive slope, a wedge cell with negative slope, and a parallel cell. The length of the cholesteric liquid crystal pitch could be elongated up to 10 nm, allowing the lasing behavior of continuous or discontinuous spatial tuning determined by the boundary conditions of the cholesteric liquid crystal cell. In the wedge cell with positive slope, the authors demonstrated a continuous spatial laser tuning in the near full visible spectral range, with a tuning resolution less than 1 nm by pumping with only a single 355 nm laser beam. This continuous tuning behavior is due to the fact that the concentration of pitch gradient matches the fixed helical pitch determined by the cell thickness. This characteristic continuous spatial laser tuning could be confirmed again by pumping with a 532 nm laser beam, over 90 nm in the visible spectral range. The scheme of the spatial laser tuning in the wedge cell bearing a pitch gradient enabled a route to designing small-sized optical devices that allow for a wide tunability of single-mode laser emissions.
Semiconductor Laser Multi-Spectral Sensing and Imaging  [PDF]
Han Q. Le,Yang Wang
Sensors , 2010, DOI: 10.3390/s100100544
Abstract: Multi-spectral laser imaging is a technique that can offer a combination of the laser capability of accurate spectral sensing with the desirable features of passive multispectral imaging. The technique can be used for detection, discrimination, and identification of objects by their spectral signature. This article describes and reviews the development and evaluation of semiconductor multi-spectral laser imaging systems. Although the method is certainly not specific to any laser technology, the use of semiconductor lasers is significant with respect to practicality and affordability. More relevantly, semiconductor lasers have their own characteristics; they offer excellent wavelength diversity but usually with modest power. Thus, system design and engineering issues are analyzed for approaches and trade-offs that can make the best use of semiconductor laser capabilities in multispectral imaging. A few systems were developed and the technique was tested and evaluated on a variety of natural and man-made objects. It was shown capable of high spectral resolution imaging which, unlike non-imaging point sensing, allows detecting and discriminating objects of interest even without a priori spectroscopic knowledge of the targets. Examples include material and chemical discrimination. It was also shown capable of dealing with the complexity of interpreting diffuse scattered spectral images and produced results that could otherwise be ambiguous with conventional imaging. Examples with glucose and spectral imaging of drug pills were discussed. Lastly, the technique was shown with conventional laser spectroscopy such as wavelength modulation spectroscopy to image a gas (CO). These results suggest the versatility and power of multi-spectral laser imaging, which can be practical with the use of semiconductor lasers.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.