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Laser Resonator
Published in Andrei Khrennikov, Social Laser, 2020
In laser physics, one of the main problems in creating laser is approaching population inversion. However, population inversion is not enough to generate a laser effect. Stimulated and spontaneous emissions are compete with each other. Thus, before becoming an amplifying device, a gain medium pumped by an external energy source is first radiated as a usual electric “lamp.” Here, spontaneous emission is dominating. The light power is distributed over a variety of frequencies and directions of propagation, generally uniformly distributed. It is the optical cavity, the laser resonator, that creates the conditions necessary for stimulated emission to become predominant over spontaneous emission. The cavity or resonator is composed of two mirrors (Fig. 3.1) that bounce the beam back and forth through the gain medium. One of the mirrors is only partially reflecting (the left-hand side mirror) and another is totally reflecting (the right-hand side mirror).
2 Lasers
Published in Peter K. Cheo, Handbook of Molecular Lasers, 2018
In most laser devices, stimulated emission is used to convert energy stored in a collection of atoms or molecules in an excited state (the laser medium) to coherent light. In some cases the stored energy originates from a chemical reaction in the laser medium. Usually, however, the energy is delivered to the laser medium by an intermediate energy carrier (e.g., photons, electrons, ions) and the “prime” energy source is electrical. For high-power devices, the efficiency of the energy transfer processes and the quantum efficiency of the laser itself can become an important consideration (e.g., high-power lasers for inertial confinement fusion or for application to Strategic Defense Initiative programs). Indeed, the bulk of the cost for such devices will be in their associated power supply and optical subsystems. Costs of about $1000 per watt for average-power devices and $10−6 per watt for peak power are typical today and, within an order of magnitude, apply to most developed high-power laser systems.
Active Optical Waveguides
Published in María L. Calvo, Vasudevan Lakshminarayanan, Optical Waveguides, 2018
Stimulated emission of light is a process whereby an atom or a molecule undergoes a transition from higher to lower energy states as a result of the presence of external stimulating photons and is key to the functionalities of both laser emission and optical gain devices. Although the idea of stimulated emission goes as far back as to Bohr and Einstein [1], the invention of the laser did not take place until the 1960s when Basov, Prokchorov, Schawlow, Townes, and Maiman [2] transformed it into reality. Similarly Gabor’s idea of holography [3] did not materialize in a practical version until decades later, when it was made possible by the arrival of the laser. Kao and Hockham’s [4] optical fiber as a new transmission medium was preceded by pioneering studies of Hondros and Debye [5].
Use of lasers in minimally invasive spine surgery
Published in Expert Review of Medical Devices, 2018
The term ‘laser’ is an acronym for light amplification by stimulated emission of radiation [15,16]. Lasers differ from other sources of light by their spatial and temporal coherence. Spatial coherence allows a laser beam to be focused to a very tiny spot, enabling applications such as laser cutting and lithography. It also enables a laser beam to remain narrow over a great distance (collimation), enabling applications such as laser pointers. Temporal (or longitudinal) coherence is the capacity to have to a polarized wave at a single frequency whose phase is correlated over a relatively great distance along the beam. It allows a laser beam to emit a single color of light and can be used to produce pulses of light as short as a femtosecond. The main components of the laser are a gain medium, a mechanism to energize it, and an optical resonator, which usually consists of two mirrors. The light of a specific wavelength that passes through the gain medium is amplified by way of stimulated emission.
Light, the universe and everything – 12 Herculean tasks for quantum cowboys and black diamond skiers
Published in Journal of Modern Optics, 2018
Girish Agarwal, Roland E. Allen, Iva Bezděková, Robert W. Boyd, Goong Chen, Ronald Hanson, Dean L. Hawthorne, Philip Hemmer, Moochan B. Kim, Olga Kocharovskaya, David M. Lee, Sebastian K. Lidström, Suzy Lidström, Harald Losert, Helmut Maier, John W. Neuberger, Miles J. Padgett, Mark Raizen, Surjeet Rajendran, Ernst Rasel, Wolfgang P. Schleich, Marlan O. Scully, Gavriil Shchedrin, Gennady Shvets, Alexei V. Sokolov, Anatoly Svidzinsky, Ronald L. Walsworth, Rainer Weiss, Frank Wilczek, Alan E. Willner, Eli Yablonovitch, Nikolay Zheludev
The laser uses stimulated emission to get amplification of radiation. But there is another way to get amplification of radiation via cooperative Dicke superradiance [243] [236]. Thus, we ask: Can we get a new kind of high frequency light source amplification using superradiance? And if so, is it related to negative mass?
Laser ablation for material processing
Published in Radiation Effects and Defects in Solids, 2022
M. Cutroneo, V. Havranek, A. Mackova, P. Malinsky, L. Silipigni, P. Slepicka, D. Fajstavr, L. Torrisi
LASER is the acronym of light amplification by stimulated emission of radiation. It is a coherent and monochromatic source of electromagnetic radiation characterized by straight propagation with negligible angular divergence. The laser theory starts with Einstein (1) and less than 50 years later Maiman (2) realized the first laser and obtained the Nobel Prize. Since then, semiconductor (Nd:YAG), gas (CO2) and dye lasers (solutions of dyes in water/alcohol and other solvents) were designed and fabricated with an increasing intensity, shorter pulse duration, better durability and more compact dimensions. The wavelengths of lasers cover from the far infrared to the soft X-ray, pulse duration from millisecond to femtosecond, maximum power approaches about 1 PW and the maximum laser intensity may exceed 1020 W/cm2. Among the first subjects addressed in the laser–matter interaction, there were the studies of the laser ablation processes, the scaling laws as a function of the laser intensity and laser wavelength. Typically, when a laser light is incident on a solid target, a plasma is generated (3), whose maximum density depends on laser parameters and the target features. The focused laser beam impinges on a solid target, inducing a rise in temperature in the irradiated spot resulting in melting, ejection of material and generation of a plasma plume. The interaction (4) of a high-power laser with a solid target generates hot plasma, high electromagnetic fields, ions and electrons. These last can be accelerated to the velocities close to the speed of light and produce collimated beams of high energy, like those obtained by conventional accelerators. The particle accelerating fields are more times higher than in conventional accelerators (of the order of 1 GV/cm); electrons or ions can be accelerated to the energies from MeV to GeV in distances shorter than 1 cm; particle currents can be tens of ampere and particle current densities above 1 GA/cm2. These significant characteristics are promising for plenty of applications from fundamental physics (5) to laser ion sources (6) to proton therapy (7).