Ultraslow light in a room-temperature solid
DOI: 10.1063/1.4797044
Has been generated. In recent years, light has been greatly slowed in gases, Bose-Einstein condensates, and solids at cryogenic temperatures (see, for example, Physics Today, July 1999, page 17 , and March 2001, page 17 ). Typically, the technique of electromagnetically induced transparency is used to create large variations in the medium’s index of refraction over a very narrow spectral range. Now, physicists at the University of Rochester have used a different technique—coherent population oscillations—to achieve the same result in a ruby crystal at room temperature. The scientists modulated the ground-state electron population at the beat frequency of two pulsed lasers. A spectral “hole” only about 36 Hz wide developed in the ruby’s absorption and the light’s group velocity was slowed to 57.5 m/s. The researchers could control the velocity by changing either the modulation frequency or the input intensity. In fact, they found that two pulses were not even necessary: A single very intense pulse could interact with itself to produce the desired effect. A possible application is to optical delay lines in the telecommunication industry. (
