Lasers and Holography
摘要
The word LASER stands forHolography the Light Amplification by Stimulated Emission of Radiation. When the stimulated emission occurs in the microwave region of the electromagnetic spectrum, it is termed as the MASER, which stands for the Microwave Amplification by Stimulated Emission of Radiations. While considering the equilibrium between matter and radiation, Einstein found that the usual absorption and emission (now called, spontaneous emission) processes alone were not sufficient to explain the equilibrium.