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Contemporary Physics

Masers

K W H Stevens

Published Oct 1, 1960• 0 citations
Publisher

Abstract

Summary This article is intended to give the reader some understanding of why masers have suddenly become of such great interest. It begins with an account of the background to the problem of microwave amplification and then passes to a description of the properties of the populations of energy levels in thermal and other kinds of equilibrium. Particular attention is paid to the way in which a population reversal can be used for amplification, the basis of the maser. The next considerations are related to the performance characteristics to be anticipated and the article ends with descriptions of the ammonia maser, the ruby 3-level maser and a brief mention of the 2-level maser work. In having to choose between describing the technological and physical problems which are involved the basic physics has seemed of more importance and has been stressed.

DOI
10.1080/00107516008202622

Related papers

Microwave and optical masers

J. E. Geusic, H. E. D. Scovil

The subject of masers is introduced by giving an historical account of events which led to the amplification of microwave radiation by an inverted population in a system of weakly interacting ammonia molecules. The introduction also outlines the development of masers up to the present. Sections 2 and 3 are concerned with maser fundamentals. Methods for obtaining inverted populations are discussed in § 2. Section 3 is devoted to the theory of maser gain and noise. This is followed by a discussion of microwave solid state masers. Microwave maser materials and the development of unidirectional travelling wave maser amplifiers are emphasized. Optical masers are treated in § 5. In this section the theory of optical amplifiers and oscillators is outlined. Also included in the theoretical discussion is a rather lengthy consideration of pump power requirements in optically pumped masers. This is followed by a survey of solid state, semiconductor and gaseous optical masers. The review ends with some comments on the extension of masers to new wavelength regions.

Reports on Progress in Physics•Jan 1, 1964•11 citations

The Physics of the Solid-State Maser

D. Howarth

Since the demonstration of the possibility of achieving very low noise amplification of signals in the centimetric wavebands, a great deal of work has been carried out in various laboratories with a view to producing and testing devices. The major part of the present article focuses attention on one particular device, the three-level solid-state maser. The physical principles underlying the process of stimulated emission of radiation are in many cases unfamiliar to electronic engineers, and study of the growing literature on the subject can be confusing without a clear understanding of the physics involved. The present article outlines the general theory of emission and radiation processes, particularly as they apply to the microwave spectrum. A quantum mechanical description is employed throughout, and a brief and not very rigorous account is given of the relevant portions of this theory as it applies to the investigation of transistors between energy levels. Well-known expressions are derived for the operating characteristics of a three-level maser, particular attention being given to the significance of the various factors involved and their relationship to easily measured quantities. Little information is included concerning practical maser amplifiers; at the time of writing, few practical devices had been constructed. A survey of recent literature indicates the rapid progress which has since been made, and shows the interest in the development of masers.

IRE Transactions on Component Parts•Jun 1, 1959•1 citation

The optical maser

C. G. B. Garrett

A brief description is presented of a solid-state device, a ruby maser, that utilizes the principles of microwave amplification by stimulated emission of radiation (maser). Experiments under way point to a new medium of communication in which a beam of light is used to transmit vast amounts of information from one point to another.

Electrical Engineering•Apr 1, 1961•2 citations

Cross-Relaxation Masers

G S Bogle

A survey is made of the available ways of using ruby, spinel, rutile and emerald in masers which amplify at frequencies small compared to their zero-field splitting frequencies. Particular attention is paid to means of taking advantage of cross relaxation which, it is shown, can give typically a two-fold improvement in maser performance. Analytic expressions for the energies are given which, to a large extent, remove the need for machine computations in the design of masers of this type.

Proceedings of the IRE•Mar 1, 1961•9 citations

The Solid State Maser

C R Ditchfield

J W Orton, D H Paxman and J C Walling Oxford: Pergamon 1970 pp ix + 280 price £2.25 (cloth) £1.75 (paper) This book, one of the 'Selected readings in physics' series, introduces the theory of solid state masers and then presents some of the important papers on the subject, to illustrate the way in which development occurred. The first chapter of part I covers the theory of interaction between radiation and matter, leading to the basic equations for the transition rates between the populations of energy levels on which maser action depends.

Physics Bulletin•Feb 1, 1971•4 citations

Performance analysis of diamond-based masers

Alexander Sherman, Lotem Buchbinder, Siyuan Ding +1 more

Masers, the microwave analog of lasers, are an important class of devices that can be used to generate highly coherent and stable microwave signals as well as quantum-limited amplification of microwave photons. Recently, the interest in such devices has increased, probably owing to experiments demonstrating the successful operation at room temperature of solid-state maser employing defects in diamond. These defects, called nitrogen vacancy (NV) centers, are comprised of a negatively charged substitutional nitrogen that replaces one of the diamond crystal lattice’s carbons and a vacancy adjacent to the excluded carbon atom. The performance of diamond-based masers, in terms of gain, noise, bandwidth, frequency of operation, and saturation, greatly depends upon the specific diamond crystal composition and its geometry in the respective microwave device. The currently available data on these issues are scarce and sometimes conflicting. It is, therefore, important to provide additional experimental data, complemented by theoretical analysis, to further optimize the required diamond material and thus enhance the capabilities of diamond-based maser technology. The latter is currently limited to operate only as an oscillator at very small bandwidths, with low saturation power. Here, we provide experimental results on a set of important parameters affecting diamond maser operation, such as the population and linewidth of the electron spin energy levels of the NVs under light illumination, as well as their relaxation times for several different diamond material compositions. These results are then used to point out which diamond material compositions and crystal geometry may be best suitable for maser-type applications.

Journal of Applied Physics•Apr 14, 2021•10 citations
Summary This article is intended to give the reader some understanding of why masers have suddenly become of such great interest. It begins with an account of the background to the problem of microwave amplification and then passes to a description of the properties of the populations of energy levels in thermal and other kinds of equilibrium. Particular attention is paid to the way in which a population reversal can be used for amplification, the basis of the maser. The next considerations are related to the performance characteristics to be anticipated and the article ends with descriptions of the ammonia maser, the ruby 3-level maser and a brief mention of the 2-level maser work. In having to choose between describing the technological and physical problems which are involved the basic physics has seemed of more importance and has been stressed.
The subject of masers is introduced by giving an historical account of events which led to the amplification of microwave radiation by an inverted population in a system of weakly interacting ammonia molecules. The introduction also outlines the development of masers up to the present. Sections 2 and 3 are concerned with maser fundamentals. Methods for obtaining inverted populations are discussed in § 2. Section 3 is devoted to the theory of maser gain and noise. This is followed by a discussion of microwave solid state masers. Microwave maser materials and the development of unidirectional travelling wave maser amplifiers are emphasized. Optical masers are treated in § 5. In this section the theory of optical amplifiers and oscillators is outlined. Also included in the theoretical discussion is a rather lengthy consideration of pump power requirements in optically pumped masers. This is followed by a survey of solid state, semiconductor and gaseous optical masers. The review ends with some comments on the extension of masers to new wavelength regions.
Since the demonstration of the possibility of achieving very low noise amplification of signals in the centimetric wavebands, a great deal of work has been carried out in various laboratories with a view to producing and testing devices. The major part of the present article focuses attention on one particular device, the three-level solid-state maser. The physical principles underlying the process of stimulated emission of radiation are in many cases unfamiliar to electronic engineers, and study of the growing literature on the subject can be confusing without a clear understanding of the physics involved. The present article outlines the general theory of emission and radiation processes, particularly as they apply to the microwave spectrum. A quantum mechanical description is employed throughout, and a brief and not very rigorous account is given of the relevant portions of this theory as it applies to the investigation of transistors between energy levels. Well-known expressions are derived for the operating characteristics of a three-level maser, particular attention being given to the significance of the various factors involved and their relationship to easily measured quantities. Little information is included concerning practical maser amplifiers; at the time of writing, few practical devices had been constructed. A survey of recent literature indicates the rapid progress which has since been made, and shows the interest in the development of masers.
J W Orton, D H Paxman and J C Walling Oxford: Pergamon 1970 pp ix + 280 price £2.25 (cloth) £1.75 (paper) This book, one of the 'Selected readings in physics' series, introduces the theory of solid state masers and then presents some of the important papers on the subject, to illustrate the way in which development occurred. The first chapter of part I covers the theory of interaction between radiation and matter, leading to the basic equations for the transition rates between the populations of energy levels on which maser action depends.
Masers, the microwave analog of lasers, are an important class of devices that can be used to generate highly coherent and stable microwave signals as well as quantum-limited amplification of microwave photons. Recently, the interest in such devices has increased, probably owing to experiments demonstrating the successful operation at room temperature of solid-state maser employing defects in diamond. These defects, called nitrogen vacancy (NV) centers, are comprised of a negatively charged substitutional nitrogen that replaces one of the diamond crystal lattice’s carbons and a vacancy adjacent to the excluded carbon atom. The performance of diamond-based masers, in terms of gain, noise, bandwidth, frequency of operation, and saturation, greatly depends upon the specific diamond crystal composition and its geometry in the respective microwave device. The currently available data on these issues are scarce and sometimes conflicting. It is, therefore, important to provide additional experimental data, complemented by theoretical analysis, to further optimize the required diamond material and thus enhance the capabilities of diamond-based maser technology. The latter is currently limited to operate only as an oscillator at very small bandwidths, with low saturation power. Here, we provide experimental results on a set of important parameters affecting diamond maser operation, such as the population and linewidth of the electron spin energy levels of the NVs under light illumination, as well as their relaxation times for several different diamond material compositions. These results are then used to point out which diamond material compositions and crystal geometry may be best suitable for maser-type applications.