Search

This report presents the results of an experiment investigating the transmission of intense femotosecond pulses on the 1445-nm resonance of water. The goal was to detect the presence of resonant bleaching behavior, which could explain the results observed by Fox and Oesterberg in 2005 at the 800-nm wavelength., Prepared in collaboration with Naval Research Laboratory (NRL), Washington, DC. The original document contains color images.

The recent interest in precursors has been fuelled by the possibility of using them for the efficient transmission of information through absorbing media at radio or optical frequencies. Here we demonstrate that the low attenuation experienced by the Brillouin precursor is attributed to the inherently low absorption of dispersive media near DC, a characteristic already exploited with communications systems using the extremely low frequency (ELF) band. Pulses, regardless of their temporal width and carrier frequency, always obey Beer's law as long as they propagate in the linear time invariant regime. We conclude with an FDTD simulation of the Maxwell-Bloch equations that shows how optical coherent bleaching effects, which take place in the linear time variant regime of the Lorentz oscillator model, can cause sustained deviations from Beer's law over relatively long distances of water.

We present a qualitative description of the precursor phenomena to place their ex- istence in the context of a practical application. We assert that precursors are nothing more than the time-domain representation of a linear broadband Beer's law. We support this description with absorption measurements of femtosecond pulses through 7 meters of water, and suggest that further deviations from Beer's law in water may be observed due to saturation effects. Copyright © (2008) by the Electromagnetics Academy.

We show how transmission through 5.7 meters of water varies with pulse energy and temporal width. 3 orders increase in transmission is observed compared with Beer's law predictions. The experimental results are compared with 0π-pulses. © 2007 Optical Society of America.