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The Use of Microwaves, Plasma and Laser for Wood Modification
Published in Dick Sandberg, Andreja Kutnar, Olov Karlsson, Dennis Jones, Wood Modification Technologies, 2021
Dick Sandberg, Andreja Kutnar, Olov Karlsson, Dennis Jones
High-power microwave sources use specialised vacuum tubes to generate microwaves, where the ballistic motion of the electrons in a vacuum is under the influence of controlling electric or magnetic fields. The most common example of such a tube is the household microwave oven. These devices use a density-modulated mode, where groups of electrons travel together, as opposed to a continuous stream of electrons. Low-power sources use solid-state to generate the microwaves. A maser is an instrument similar to a laser, amplifying microwaves in a manner similar to how a laser amplifies light waves.
Elements of Quantum Electronics
Published in Michael Olorunfunmi Kolawole, Electronics, 2020
In principle, we can turn an amplifier into an oscillator by providing positive feedback, which can be realized using a pair of plane or concave spherical mirrors. In masers, the active medium is placed into a microwave cavity [12]. Technically, a maser oscillator requires a source of excited atoms or molecules and a resonator to store their radiation. The excitation must force more atoms or molecules into the upper energy level (or energy state) than in the lower, in order for amplification by stimulated emission to predominate over absorption. There are application areas where maser is used, including satellite communication, air-to-air communication, radio technology, amplifiers, and oscillators in microwave, where low noise factor is the most important.
Historical Facts toward Introduction of Fiber-Optics and Photonics
Published in Tarun Kumar Gangopadhyay, Pathik Kumbhakar, Mrinal Kanti Mandal, Photonics and Fiber Optics, 2019
In 1954, the “MASER” was developed by Charles Townes and his colleagues at Columbia University. Maser stands for “microwave amplification by stimulated emission of radiation” [20–22]. In 1958, the first LASER was invented by the same group of Physicists, Charles Townes and Arthur Schawlow [20]. LASER stands for “light amplification by stimulated emission of radiation.” It is a very efficient and high-powered coherent light source. Basically, light is reflected back and forth in an energized medium to generate amplified light as opposed to excited molecules of gas amplified to generate waves.
Efficient transfer of inversion doublet populations in deuterated ammonia using adiabatic rapid passage
Published in Molecular Physics, 2022
S. Herbers, Y. M. Caris, S. E. J. Kuijpers, J.-U. Grabow, S. Y. T. van de Meerakker
Ammonia is a molecule with a rich history in the physical sciences. In the chemical community the role of the Haber–Bosch process to convert nitrogen into ammonia for the production of fertiliser is well recognised. In the physics community ammonia is most renowned for its use in the original molecular beam maser (Microwave Amplification by Stimulated Emission of Radiation) setup. Proposed by Townes's group in 1951, it was first supposed to work with ND but was realised in 1954 with NH instead [1,2]. The development of the maser is of particular historic importance because it laid the foundation of all laser (Light Amplification by Stimulated Emission of Radiation) technology, with the first laser realised in 1960 by Theodore Maiman [3]. In astrophysics, ammonia is of pivotal importance because it was not only the first molecule to be observed with microwave spectroscopy in the laboratory in 1934 [4], but also was the first polyatomic molecule observed in space in 1968 [5], whereas ND was the first triply deuterated species identified in the interstellar medium in 2002 [6]. Observed emissions from rotational transitions are frequently used to probe the temperature of molecular clouds [7]. More recently, ammonia has become a molecule of primary importance in cold molecule research, as its pronounced first-order Stark effect allows for easy control in electric fields [8]. Decelerators [9], bunchers [10], traps [11–16], guides [17–19], storage rings [20] and synchrotrons [21] have been demonstrated using ND, and controlled samples of ammonia have been used in novel collision experiments [22–26] and for high resolution spectroscopy [13] alike.