China
Africa
Explore chapters and articles related to this topic
Electrical Properties of Metals and Semiconductors
Published in Yip-Wah Chung, Monica Kapoor, Introduction to Materials Science and Engineering, 2022
When we pass a current through a pn junction in the forward-bias configuration, we are pushing electrons from the n to the p side and holes from the p to the n side. In other words, we are injecting minority charge carriers, which may recombine with carriers of the opposite sign. With certain semiconductors such as gallium arsenide and gallium nitride, the recombination results in the emission of light, which is the basis of the LED. Commercial LEDs with electrical-to-light energy conversion efficiency ~20%–25% are now (2021) available at reasonable prices. With sufficient currents and proper geometry to provide an optical cavity in which light amplification can occur, a solid-state laser is produced. These solid-state lasers are widely used in data storage, entertainment (audio and video), and optical communications.
Basic Concepts Concerning the Properties of Real Resonators and the Processes Occurring in Them
Published in Yurii A. Anan'ev, Laser Resonators and the Beam Divergence Problem, 2020
Thermal deformations are particularly large in the active elements of lasers operating in a periodic (Anan'ev et al 1966b, Grishmanova et al 1967) or cw (Roess 1966) mode. However, even when operating under single-pulse conditions, thermal deformations may reach a noticeable level at the end of the pulse and, thus, affect considerably the angular divergence of radiation. Indeed, in an earlier study of Vanyukov et al (1965b) made on a comparatively small neodymium glass laser at a moderate pumping level the divergence was observed to grow to twice its original value at the end of the laser pulse, an effect correctly attributed to thermal phenomena. As solid state lasers grew both in size and power, counteracting the thermal deformations became a problem of paramount importance in laser technology. The method used to solve this problem, as well as some other aspects of the issue of optical inhomogeneities in active media, will be treated in more detail in Chapter 6. Note only that similar phenomena are observed also in high-power gas lasers, namely the microinhomogeneities arising in the process of excitation of a gas medium or in its turbulent motion quite frequently produce noticeable light scattering; in place of thermal deformations of the active element one has here those of the resonator mirrors (section 6.1.1).
Laser Sources Based on Gaseous, Liquid, or Solid-State Active Media
Published in Helmut H. Telle, Ángel González Ureña, Laser Spectroscopy and Laser Imaging, 2018
Helmut H. Telle, Ángel González Ureña
The most common dopants belong to the group of lanthanide rare-earth elements, such as erbium (Er) or neodymium (Nd), because the excited states of their ions couple only weakly with the (thermal) phonons of their crystalline host lattices (phonons), and thus losses are relatively low, which as a consequence also means low pumping thresholds. Since the ruby laser was demonstrated just over 50 years ago, laser action has been demonstrated in literally hundreds of solid-state media; however, only a few are in widespread use. Probably the best-known and widely used solid-state laser material is neodymium-doped yttrium aluminum garnet or Nd:YAG; lasers based on Nd-doped active media will be discussed further below.
Renovating electrical power-to-TEM00 mode laser power conversion efficiency with four-lamp/four-rod pumping scheme
Published in Journal of Modern Optics, 2021
Miguel Catela, Dawei Liang, Cláudia R. Vistas, Dário Garcia, Bruno D. Tibúrcio, Hugo Costa, Joana Almeida
In the beginning of laser technology, noble gas lamps were already well known and widely used. Their low cost, high radiative power and good reliability made them optimum pump sources in the first laser inventions, the ruby laser built by Maiman [1], and the first Nd:YAG laser reported by Geusic et al. [2]. In fact, lamp technology was used in almost every single innovation with solid-state active media [3–7]. Moreover, dye lasers were also studied by resorting to lamp optical pumping [8–10]. In the industry, lamp-pumped solid-state laser systems were extensively used for marking, drilling, or cutting over the last decades [11–17]. Although diode-pumped lasers have become very common due to their superior efficiency, the main disadvantage of diode pumping (as compared with lamp pumping) is the significantly higher cost per watt of pump power. For this reason, lamp-pumped lasers are still used in cases where high powers are needed. For example, lamp-pumped Q-switched Nd:YAG lasers are still widely used for laser marking and will not be replaced by diode-pumped lasers in the near future. For nuclear fusion research, Lawrence Livermore National Laboratory pumped their most powerful laser systems with flash lamps [18–20].
Laboratory spray drying of materials for batteries, lasers, and bioceramics
Published in Drying Technology, 2019
C. Arpagaus, A. Collenberg, D. Rütti
In solid-state lasers, yttrium aluminum garnet (YAG, Y3Al5O12) is commonly used as host material. Rare earth elements such as ytterbium (Yb), erbium (Er), praseodymium (Pr), or neodymium (Nd) are doped into YAG as active laser ions, which determine the light absorption and emission profiles. For example, Nd:YAG emits infrared light at a wavelength of 1,064 nm and provides output power levels up to the kW range.[23] Yb:YAG lasers emit at 1,030 nm and are good substitutes for Nd:YAG in high-power applications. Er:YAG is lasing at 2,940 nm and couples well into water and body fluids making this laser especially useful for medicine and dentistry uses.[25] In comparison, Pr:YAG lasers offer interesting perspectives for applications in optics and photonics, for example, in the field of scintillator materials, to count the energy and intensity of ionizing radiation.[20]
Producing a thin coloured film on stainless steels – a review. Part 2: non-electrochemical and laser processes
Published in Transactions of the IMF, 2023
G. T. Alliott, R. L. Higginson, G. D. Wilcox
Variations on the type of laser used exist between authors. Earlier investigations by Sugioka et al.38,39 and Maeda et al.37 use krypton fluoride (KrF) and high-powered CO2 lasers respectively. KrF lasers are a type of excimer laser which are made up of a noble gas and a halogen, in this case krypton and fluorine.55 More recent studies by Shin et al.,42 Chang et al.43 and Veiko et al.44 have utilised ytterbium fibre lasers, a type of solid state laser. Solid state lasers are known to exhibit high beam quality and require little maintenance.56