| 释义 |
▪ I. maser|ˈmeɪzə(r)|
[An acronym: see quot. 19552.]
A laser, esp. one that emits microwaves.
The first masers emitted microwaves. Later ones emitted in other parts of the spectrum, and these were also called masers for a time until laser came to be adopted as the general name for all such devices.
1955Sci. News Let. 5 Feb. 83/1 Scientists can, for the first time, generate microwaves of extremely high frequency by tapping directly the energy of molecules, Dr. Charles H. Townes of Columbia University's physics department reported in New York. His device for doing so is known as the ‘maser’. Ibid., Work on the maser began three years ago. 1955Gordon, Zeiger, & Townes in Physical Rev. 15 Aug. 1264/1 The device utilizes a molecular beam in which molecules in the excited state of a microwave transition are selected. Interaction between these excited molecules and a microwave field produces additional radiation and hence amplification by stimulated emission. We call an apparatus utilizing this technique a ‘maser’, which is an acronym for ‘microwave amplification by stimulated emission of radiation’. 1958Schawlow & Townes in Ibid. 15 Dec. 1940 (heading) Infrared and optical masers. 1960Times 17 Oct. 2/2 (Advt.), Development work on existing long range programmes in: solid-state millimetre and optical masers, parametric amplifiers, [etc.]. 1960,1962[see laser2]. 1962Engineering 2 Feb. 190/2 The basic type of maser, from which the principle of optical masers is derived, is a quite recent electron device... Research later extended the upper frequency range of this technique of low-noise signal amplification, until it eventually reached the visible region—giving rise to the optical maser, otherwise known as the laser. 1967T. P. Melia Introd. Masers & Lasers iv. 34 The power output of the ammonia maser is very small (about 10-10 watt) but the frequency stability is of the order of 1 in 1012 over a 1 minute period and 1 part in 1010 over very much longer periods. 1968Nature 30 Mar. 1237/2 (heading) Is interstellar hydrogen capable of maser action at 21 centimetres? 1969S. G. & H. Lipson Optical Physics xi. 369 A maser is, of course, a very-narrow-band amplifier; it is because of its narrow band that the noise-level achieved is very low, since there is a theoretical minimum noise-level per unit band-width. 1972Sci. Amer. Sept. 136/3 The greatest contributor..to the receiver's ability to handle Telstar's faint signals (about 10-12 watt) was a maser amplifier that combined very high gain with extremely low noise.
▪ II. maser
variant of mazer. |