title: Inactivation of viruses by coherent excitations with a low power visible femtosecond laser.
abstract: BACKGROUND
  Resonant microwave absorption has been proposed in the literature to excite the vibrational states of microorganisms in an attempt to destroy them. But it is extremely difficult to transfer microwave excitation energy to the vibrational energy of microorganisms due to severe absorption of water in this spectral range. We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M13 through impulsive stimulated Raman scattering.
  
  
  CONCLUSIONS
  By using a very low power (as low as 0.5 nj/pulse) visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW/cm2. The inactivation of M13 phages was determined by plaque counts and had been found to depend on the pulse width as well as power density of the excitation laser.
  
  
  CONCLUSIONS
  Our experimental findings lay down the foundation for an innovative new strategy of using a very low power visible femtosecond laser to selectively inactivate viruses and other microorganisms while leaving sensitive materials unharmed by manipulating and controlling with the femtosecond laser system.
authors.affiliation: Department of Physics, Arizona State University, Tempe, AZ 85287, USA. tsen@asu.edu
authors.forename: K T
authors.initials: KT
authors.lastname: Tsen
authors.forename: Shaw-Wei D
authors.initials: SW
authors.lastname: Tsen
authors.forename: Chih-Long
authors.initials: CL
authors.lastname: Chang
authors.forename: Chien-Fu
authors.initials: CF
authors.lastname: Hung
authors.forename: T-C
authors.initials: TC
authors.lastname: Wu
authors.forename: Juliann G
authors.initials: JG
authors.lastname: Kiang
mesh_terms: D017104:Bacteriophage M13 / Q000528:radiation effects*; D007834:Lasers; D008027:Light; D050296:Microbial Viability; D013059:Spectrum Analysis, Raman; D010948:Viral Plaque Assay; D038301:Virus Inactivation