COHERENT LIGHT AMPLIFIERS

The feasibility of realizing light amplification without forming an image on a focal surface before amplification and transfer thereof is examined. Such a coherent light amplifier could only be realized by applying stimulated emission maser processes and techniques. The severe limitations imposed by the spontaneous emission from the excited medium are calculated in detail for imaging devices. Detailed calculations of input power requirements, impurity concentrations, and the possibility of utilizing ambient night illumination are given in the visible and infrared regions of the spectrum. The severity of the attendant problems of image conversion of amplified radiation in the non-visible portion of the spectrum are realized. Available data on the luminescence of objects in moonlight or starlight indicate there is insufficient ambient radiation after dark to overcome photon noise in the narrow band regions of such devices. As an active device with the target artificially illuminated, the amount of energy needed to attain unity signal-to-noise ratio is so great that in the visible region of the spectrum the eye can operate alone without any amplification of the return radiation. Author