Laser beam combiner: applications to space-borne laser communications

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Optical Communications

Background:

• Directly modulated single-mode Gallium Aluminum Arsenide/Gallium Aluminum Arsenide (GaAs/GaAlAs) injection lasers are promising for spaceborne laser communications.
• Existing GaAlAs lasers suffer from low power output per diode and significant beam divergence, limiting their application.
• Overcoming these limitations is crucial for advancing high-bandwidth space communication systems.

Purpose of the Study:

• To introduce and evaluate a simple optical concept for a laser beam combiner.
• To address the limitations of low power and wide beam divergence in GaAlAs diode lasers.
• To demonstrate a method for improving laser beam quality and power for optical communication.

Main Methods:

• A novel optical concept utilizing an array of closely packed, parallel, collimated laser beams was designed.
• The combined beam array was integrated into an optical system, treating it as a single beam.
• Far-field performance was analyzed, considering diffractive spreading and power addition.

Main Results:

• The optical concept effectively handles an array of laser beams as a single unit.
• Diffractive spreading ensures all beams overlap in the far field.
• Incoherent power addition results in 50% power throughput with good far-field performance.

Conclusions:

• The developed laser beam combiner effectively overcomes limitations of individual GaAlAs diodes.
• The system offers a viable solution for enhancing power and beam quality in spaceborne laser communications.
• The approach demonstrates good far-field performance, making it suitable for demanding optical applications.