Propagation of ultrashort laser pulses in water: linear absorption and onset of nonlinear spectral transformation.
We study propagation of short laser pulses through water and use a spectral hole filling technique to essentially perform a sensitive balanced comparison of absorption coefficients for pulses of different duration. This study is motivated by an alleged violation of the Bouguer-Lambert-Beer law at low light intensities, where the pulse propagation is expected to be linear, and by a possible observation of femtosecond optical precursors in water. We find that at low intensities, absorption of laser light is determined solely by its spectrum and does not directly depend on the pulse duration, in agreement with our earlier work and in contradiction to some work of others. However, as the laser fluence is increased, interaction of light with water becomes nonlinear, causing energy exchange among the pulse's spectral components and resulting in peak-intensity dependent (and therefore pulse-duration dependent) transmission. For 30 fs pulses at 800 nm center wavelength, we determine the onset of nonlinear propagation effects to occur at a peak value of about 0.12 mJ/cm(2) of input laser energy fluence.
Sokolov
Alexei V
AV
Institute for Quantum Studies and Department of Physics, Texas A&M University, 4242 TAMU, College Station, Texas 77843-4242, USA.
Naveira
Lucas M
LM
Poudel
Milan P
MP
Strohaber
James
J
Trendafilova
Cynthia S
CS
Buck
William C
WC
Wang
Jieyu
J
Strycker
Benjamin D
BD
Wang
Chao
C
Schuessler
Hans
H
Kolomenskii
Alexandre
A
Kattawar
George W
GW
D007834:Lasers; D016014:Linear Models; D017711:Nonlinear Dynamics; D055620:Optical Phenomena; D014867:Water
D014867:Water