Amplification of Coherent Radiation

Karl Friedrich Renk

Gabriel Laufer

Introduction Previous discussions (see Section 10.4) suggested that stimulated emission can be used to generate optical gain, that is, to amplify radiation. The reader certainly has experience in the amplification of electronic signal. For example, radio receivers capture faint radio waves and turn them into a signal that is powerful enough to drive large speakers. This electronic amplification increases the amplitude of the signal while faithfully preserving its acoustic frequencies and modulation characteristics. Similarly, optical amplification is expected to increase the amplitude of an optical signal while preserving its frequency, its modulation characteristics, and its coherence. The latter requirement is of particular significance for optical radiation, where the coherence of naturally occurring radiation rarely exceeds one micrometer. Lasers are the primary source for coherent radiation. They depend on stimulated emission for amplification and for the generation of coherent radiation (the word laser is the acronym of Light Amplification by Stimulated Emission of Radiation). For amplification, an atomic system that is part of the laser medium must be prepared with a sufficiently large number of particles in the excited state. (The term atomic system is used here to describe all microscopic systems including molecules and free electrons.) Radiation passing through that excited medium encounters multiple events of stimulated emission, each event contributing one photon that is added coherently to the propagating beam. When the number of events of stimulated emission exceed all losses by absorption or scattering, the incident radiation is amplified.

А. А. Каминский, Sergei A. Kochubei, K. N. Naumochkin +3 more

Investigations were made of the spectral and luminescence properties of the Ce 3+ ion in a BaY 2 F 8 crystal. Amplification of coherent radiation (λ = 0.345 μm) was achieved due to the 5 d 1 4 f n – 1 –4 f n interconfigurational transition when this was excited by XeCl laser radiation (λ = 0.308 μm).

Willis E. Lamb

J. Weber

This paper briefly discusses the possibility of obtaining coherent microwave radiation from crystals and gases. It will be shown that it is possible to obtain coherent microwave radiation by such methods, provided that a certain non equilibrium energy distribution is first produced. Methods are discussed for producing such a distribution. The amount of amplification which can be produced by such methods is very small Tinder ordinary circumstances and does not appear to be able to compete with other methods. The method may have certain special applications.