High-intensity rectangular fiber-coupled diode laser array for solid-state laser pumping

Area of Science:

• Optics and Photonics
• Laser Technology

Background:

• High-power diode lasers are crucial for various applications.
• Efficiently coupling diode laser output into optical fibers remains a challenge.
• Existing methods often suffer from power loss and beam degradation.

Purpose of the Study:

• To propose and validate a novel coupling scheme for high-power diode laser bars using rectangular optical fibers.
• To enhance power delivery and improve beam characteristics from diode laser sources.

Main Methods:

• A scale version of the coupling scheme was tested using an individual diode laser array and a single rectangular fiber.
• Power coupling efficiency was measured for a 1-W continuous-wave diode laser array.
• Far-field intensity patterns and divergence were analyzed before and after fiber coupling.

Main Results:

• 60% of the diode laser power was coupled into a 216 µm × 28 µm optical fiber.
• Output intensities reached 9.9 kW cm⁻².
• The elliptical, dual-lobed far-field pattern was converted to a nearly circular, single-lobed pattern with reduced divergence (21° × 22° FWHM).
• Beam quality was reduced by a factor of 30.
• Alignment tolerances exceeded 10 µm in all three planes.

Conclusions:

• The proposed rectangular optical fiber coupling scheme is effective for high-power diode laser bars.
• This method significantly improves beam quality and output intensity.
• The scheme offers practical advantages with large alignment tolerances, suitable for real-world applications.