Concept for power scaling second harmonic generation using a cascade of nonlinear crystals

Area of Science:

• Nonlinear optics
• Laser physics
• Materials science

Background:

• High-power second harmonic generation (SHG) is crucial for various applications.
• Thermal dephasing in nonlinear crystals limits power scaling in traditional SHG systems.
• Existing methods struggle to balance high efficiency with power handling capabilities.

Purpose of the Study:

• To demonstrate a novel concept for efficient power scaling in single-pass SHG beyond conventional limits.
• To overcome adverse crystal effects like thermal dephasing in high-power SHG.
• To achieve high-power, diffraction-limited green light generation from laser diodes.

Main Methods:

• Utilized a cascade of nonlinear crystals for single-pass SHG.
• Selected the first crystal for high nonlinear efficiency and subsequent crystals for power handling.
• Employed a tapered laser diode as the fundamental light source.
• Characterized the generated second harmonic (SH) light for power and beam quality.

Main Results:

• Generated 3.7 W of continuous-wave (CW) diffraction-limited (M(2)=1.25) green light (532 nm).
• Used 9.5 W of non-diffraction-limited (M(2)=7.7) fundamental light from a laser diode.
• Successfully avoided significant thermal effects, demonstrating improved power handling.
• Achieved the highest SH power reported for a laser diode source.

Conclusions:

• The cascaded nonlinear crystal approach enables efficient power scaling beyond thermal limitations.
• This method effectively combines high nonlinear efficiency with superior power handling.
• The concept is versatile, applicable to other wavelengths and scalable with additional stages.