In this chapter, high-power direct diode laser systems are becoming more and more attractive for industrial applications where they are not limited anymore to the pumping of solid-state lasers and fibres. Nonetheless, the highest power emitted from a single laser chip is typically below 20 W for a broad area element in the near infrared, and even below in other spectral ranges. Thus the high powers required for cutting, welding and other advanced manufacturing techniques are only available by combining multiple emitters in a single beam - strength lies in numbers in this matter too!

Chapter Contents:

• 2.1 Introduction
• 2.2 High-power semiconductor lasers and amplifiers used for coherent beam combining
• 2.3 Principles of coherent beam combining architectures
• 2.3.1 Phase locking
• 2.3.2 Coherent superposition
• 2.3.2.1 Tiled aperture approach: far-field superposition
• 2.3.2.2 Filled aperture approach: near-field superposition
• 2.4 Master-oscillator power amplification architectures
• 2.4.1 Coherent beam combining of amplifier arrays
• 2.4.1.1 Ridge waveguide amplifiers
• 2.4.1.2 Tapered waveguide amplifiers
• 2.4.1.3 Limitations related to coherently combined arrays
• 2.4.2 Coherent combining of individual amplifiers
• 2.4.2.1 Coherent beam combining of three high power tapered amplifiers
• 2.4.2.2 Coherent beam combining module based on commercially available amplifiers
• 2.5 Extended-cavity architectures
• 2.5.1 Principles of operation
• 2.5.2 Cavity architectures based on beam superposition
• 2.5.2.1 General description
• 2.5.2.2 Self-organisation and spectral filtering
• 2.5.2.3 Multi-arm interferometric cavities: experimental results
• 2.5.2.4 Back-side resonator configurations
• 2.5.3 Parallel coupled cavities
• 2.5.3.1 Cavities using near-field spatial filtering: the Talbot cavity
• 2.5.3.2 Cavities using far-field angular filtering
• 2.6 Conclusion
• References

Inspec keywords: laser beam cutting; semiconductor lasers; laser beam welding; laser beams

Other keywords: advanced manufacturing technique; welding technique; single laser chip; multiple emitters; coherent beam combining architectures; high-power direct diode laser systems; cutting technique

Subjects: Laser beam interactions and properties; Lasing action in semiconductors; Laser materials processing; Textbooks; Machining; Laser beam characteristics and interactions; Semiconductor lasers; Joining processes and welding; Laser materials processing; Design of specific laser systems