Laser induced water transparency for underwater, fog and cloud penetration
Abstract
Princeton will conduct experimental and theoretical studies aimed at verifying our hypothesis of the mechanism responsible for the anomalous increase of water transparency in the IR spectral region and the laser beam self-induced channeling atrelatively very low beam intensities. They suggest that the observed effects are due to the laser induced breaking of the hydrogen bonds, i.e. laser induced ~depolymerization~. Additionally, they suggest that laser induced ponderomotive compression of water creates an optical conduit resulting in laser beam channeling and propagation with significantly decreased divergence. They propose the following mechanism. The absorption of near-IR laser beam causes increase of water temperature and this results in breaking of weak hydrogen bonds. Thus, in the path of a laser beam water chains break and water becomes consistent of individual molecules, i.e. water becomes similar to vapor with the density that equals the density of condensed water. Also, the ponderomotive compression of water creates a channel with refractive index profile that has maximum at the beam axis. According to our estimates the increase of the refractive index due to ponderomotive compression exceeds by several orders of magnitude increase of refractive indexed caused by the Kerr effect. This allows beam channeling in water at low laser beam intensities.The main goals of this project are1. To verify our hypothesis that, near-IR laser beam propagating in water induces breaking of the hydrogen bonds of molecular chains due to water temperature increase. We will verify that the absorption coefficient changes with the increase of water temperature decreasing from the value measured for ~hydrogen bonded~ water (absorbing in the IR spectral region) down to the value expected for water vapor consisting of unbound molecules (highly transparent in the IR spectral region).2.To create a theoretical model that will provide a one-dimensional axisymmetric timedependent simulation of the dynamics of complex refractive index, taking into account the compressibility, heating of the liquid due to radiation absorption, and the corresponding change in transparency.3.To conduct experimental study of possibility of creation of a conduit in water by use of combination of several lasers of different wavelength (Nd:YAG at 1.06 ~m and second harmonic of Nd:YAG at 532 nm).4.To conduct experimental study of the lifetime of the laser induced conduit and to evaluate usefulness of this conduit for applications in underwater sensing, communication and wireless energy transmission.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 20, 2019
- Source ID
- N000141912594
Entities
People
- Mikhail N. Shneider
Organizations
- Office of Naval Research
- Trustees of Princeton University
- United States Navy