High brightness laser diode through open-loop spectral beam combining based on a VBG (volume Bragg grating) device.

Area of Science:

• Optics and Photonics
• Laser Technology
• Materials Science

Background:

• High-brightness laser diodes are crucial for various applications.
• Traditional spectral beam combining methods face limitations in efficiency and scalability.
• Volume Bragg gratings (VBGs) offer precise spectral selectivity and high damage threshold.

Purpose of the Study:

• To develop a novel wavelength stabilization and spectral beam combining design for fiber-coupled laser diodes (LDs).
• To enhance the brightness and power of LD-based systems.
• To achieve precise control over beam parameters for improved coupling efficiency.

Main Methods:

• Utilized miniature VBGs (0.4° diffraction angle) for spectrum locking of sub-beams.
• Employed a large-scale primary combining VBG (6° diffraction angle) for combining two sub-beams.
• Employed fiber-coupled LD modules for convenient control of beam parameters, including wavelength and spectral width.

Main Results:

• Achieved a locked spectral width of less than 0.3 nm (FWHM) for sub-beams.
• Reached a combined power exceeding 800W.
• Obtained a beam product parameter (BPP) of less than 15 mm·mrad (containing 95% energy), enabling coupling into a 200 µm core diameter fiber with NA < 0.15.

Conclusions:

• The novel VBG-based design effectively stabilizes wavelength and combines spectral beams from fiber-coupled LDs.
• The system demonstrates high power, narrow spectral width, and excellent beam quality, suitable for high-brightness applications.
• This approach offers a scalable and efficient solution for increasing laser brightness compared to direct spatial light output.