Technique to separate lidar signal and sunlight

Area of Science:

• Remote Sensing
• Optical Physics
• Atmospheric Science

Background:

• Daytime space-based lidar measurements suffer from significant backscatter noise due to sunlight.
• High surface albedo, common over land and snow, exacerbates this noise, obscuring signals from thin atmospheric constituents.
• Existing methods struggle to effectively filter out variable background sunlight.

Purpose of the Study:

• To develop a novel lidar remote sensing concept to eliminate sunlight-induced noise.
• To propose a method utilizing orbital angular momentum (OAM) laser light and a photon sieve (PS) filter.
• To numerically model the effectiveness of this concept in separating lidar signals from sunlight.

Main Methods:

• Transmitting laser light with orbital angular momentum (OAM).
• Employing a photon sieve (PS) diffractive filter to separate light components.
• Numerical modeling of Laguerre-Gaussian (LG) laser beam and plane-wave light focusing by the PS.

Main Results:

• OAM-carrying laser light focuses into a ring ('focal ring') after passing through the PS filter.
• Scattered sunlight, lacking OAM, focuses at the center and can be blocked.
• The radius of the focal ring increases with the azimuthal mode (L) of the LG laser light, enhancing signal separation.

Conclusions:

• The proposed lidar concept effectively eliminates sunlight noise by separating OAM laser light from background scattered sunlight.
• This technique holds potential for significantly improving the quality of daytime space-based lidar measurements.
• Increasing the azimuthal mode (L) of the OAM laser light offers a tunable method for optimizing noise reduction.