Superluminal and Slow Light Propagation in a Room-Temperature Solid

• Published in: Science (American Association for the Advancement of Science) Vol. 301; no. 5630; pp. 200 - 202
• Main Authors: Bigelow, Matthew S., Lepeshkin, Nick N., Boyd, Robert W.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 11-07-2003; The American Association for the Advancement of Science
• Subjects: Absorption cross sections; Alexandrite; Climate; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Crystals; Exact sciences and technology; Group velocity; Laser beams; Lasers; Light; Modulated signal processing; Observation; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other topics in optical properties of condensed matter and other interactions of matter with particles and radiation; Other topics in optical properties, condensed matter spectroscopy and other interactions of particles and radiation with condensed matter; Physics; Propagation delay; Pumps; Quantum mechanics; Quantum theory; Speed; Speed of light; Temperature; Wavelengths; United States; Superluminal velocity; Propagation velocity; Ground states; Ternary compounds; Oscillations; Quantum effect; Chromium additions; Excited states; Experimental study; Energy level population; Group velocity; Impurities; Light propagation; Beryllium oxides; Modulation; Optical attenuation; Aluminium oxides
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1084429

We have observed both superluminal and ultraslow light propagation in an alexandrite crystal at room temperature. Group velocities as slow as 91 meters per second to as fast as -800 meters per second were measured and attributed to the influence of coherent population oscillations involving chromium ions in either mirror or inversion sites within the crystal lattice. Namely, ions in mirror sites are inversely saturable and cause superluminal light propagation, whereas ions in inversion sites experience conventional saturable absorption and produce slow light. This technique for producing large group indices is considerably easier than the existing methods to implement and is therefore suitable for diverse applications.