Propagation through the ocean's surface at shallow angles with a laser beam.

Area of Science:

• Ocean optics
• Laser physics
• Underwater communication

Background:

• Optical propagation in water is challenging due to scattering and absorption.
• Shallow angle propagation near the ocean surface is particularly complex.
• Previous experimental data on long-range shallow angle laser propagation is limited.

Purpose of the Study:

• To experimentally demonstrate and quantify laser light propagation through the ocean surface at shallow angles.
• To assess the feasibility of underwater laser communication systems.
• To measure the efficiency of shallow angle laser propagation in a natural ocean environment.

Main Methods:

• Utilized a 6-mJ multipulse laser system at a depth of 1.5 meters.
• Conducted experiments in the ocean with an attenuation coefficient of approximately 3.3 m⁻¹.
• Detected laser signals at a distance of 600 meters at a 1-degree angle to the ocean surface.
• Employed statistical ray trace analysis and physical tank modeling for comparison.

Main Results:

• Successfully detected laser propagation at 600 meters from the source.
• Measured an efficiency of 3.6 x 10⁻² (joules received per receiver steradian per joule transmitted).
• Statistical ray trace analysis and physical tank modeling yielded equivalent efficiency results.

Conclusions:

• Demonstrated the practical possibility of laser propagation through the ocean surface at shallow angles.
• The results support the viability of laser-based communication systems for underwater applications.
• Experimental findings align with theoretical and modeling predictions, validating the approach.