Coherent combining of high brightness tapered amplifiers for efficient non-linear conversion

Area of Science:

• Optics and Photonics
• Laser Physics
• Nonlinear Optics

Background:

• High-power laser sources are crucial for various scientific and industrial applications.
• Coherent beam combination offers a path to scaling laser power while maintaining good beam quality.
• Efficient conversion of infrared to visible light is a key challenge in laser technology.

Purpose of the Study:

• To demonstrate a simple architecture for coherent beam combination of tapered amplifiers.
• To investigate the efficiency and beam quality improvement through coherent combination.
• To achieve efficient second harmonic generation (SHG) of the combined infrared beam into the visible spectrum.

Main Methods:

• Coherent beam combination of three tapered amplifiers seeded by a single-frequency laser at 976 nm.
• Utilizing efficiently cooled emitters in a straightforward setup.
• Employing second harmonic generation using periodically poled lithium niobate (PPLN) for frequency conversion.

Main Results:

• Maximal combined infrared power of 12.9 W achieved with > 65% combining efficiency.
• Spatial profile cleanup observed, increasing central lobe power content by up to 86%.
• High nonlinear conversion efficiency of 4.5%/W for SHG, yielding > 2 W at 488 nm.

Conclusions:

• Coherent beam combination of tapered amplifiers is an effective method for generating high-power, high-brightness infrared beams.
• The combined beam's improved spatial profile is beneficial for subsequent nonlinear processes.
• Efficient conversion to visible light at 488 nm is demonstrated, though limited by thermal effects in PPLN, indicating areas for future optimization.