Lasing without inversion

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Lasing without inversion (LWI), or lasing without population inversion, is a technique used for light amplification by stimulated emission without the requirement of population inversion.[1] A laser working under this scheme exploits the quantum interference between the probability amplitudes of atomic transitions in order to eliminate absorption without disturbing the stimulated emission,[2] this phenomenon is also the essence of electromagnetically induced transparency.[3]

The basic LWI concept was first predicted by Ali Javan in 1956,[4][5] the first demonstration of LWI was carried out by Marlan Scully in an experiment in rubidium and sodium at Texas A&M University, and then at NIST in Bolder.[6]


  1. ^ Harris, S. E. (1989). "Lasers without inversion: Interference of lifetime-broadened resonances". Physical Review Letters. 62 (9): 1033–1036. Bibcode:1989PhRvL..62.1033H. doi:10.1103/PhysRevLett.62.1033. PMID 10040407. (Subscription required (help)). 
  2. ^ Mompart, J.; Corbalán, R. (2000). "Lasing without inversion" (PDF). J. Opt. B: Quantum Semiclass. Opt. 2 (3): R7–R24. Bibcode:2000JOptB...2R...7M. doi:10.1088/1464-4266/2/3/201. (Subscription required (help)). 
  3. ^ Scully, M., & Zubairy, M. (1997). Chapter 7; in Quantum optics (p. 220). Cambridge: Cambridge University Press.
  4. ^ Scully, M., & Zubairy, M. (1997). Chapter 7; in Quantum optics (p. 245). Cambridge: Cambridge University Press.
  5. ^ A. Javan, Phys. Rev. 107, 1579 (1956)
  6. ^ Javan, A. (2000). "On knowing Marlan". In Ode to a quantum physicist: A festschrift in honor of Marlan O. Scully. Elsevier.