Optimized SESAMs for kilowatt-level ultrafast lasers

Area of Science:

• Optics and Photonics
• Materials Science
• Laser Technology

Background:

• High-power laser oscillators require robust optical components capable of handling significant thermal loads.
• Semiconductor Saturable Absorber Mirrors (SESAMs) are crucial for ultrafast laser operation but can suffer from thermal effects like deformation and lensing.
• Existing SESAM designs face limitations in managing heat at kilowatt average power levels.

Purpose of the Study:

• To investigate and compare the thermal deformation and properties of SESAMs under high-power laser operation.
• To evaluate the impact of different contacting techniques on SESAM thermal performance.
• To develop and demonstrate an improved SESAM design for kilowatt-level laser oscillators.

Main Methods:

• Comparative analysis of standard and substrate-removed SESAMs.
• Measurement of temperature rise, thermal lensing, and surface deformation under varying absorbed power.
• Utilizing a novel substrate-transfer direct bonding technique for advanced SESAM fabrication.

Main Results:

• Thermal effects in SESAMs scale linearly with absorbed power, with the contacting technique significantly influencing thermal rise and lensing.
• The novel substrate-transfer direct bonding technique yields SESAMs with negligible surface deformation and improved heat removal.
• Optimized SESAMs exhibit non-measurable radii of curvature, a significant improvement over standard designs with astigmatic ROCs up to 10 m.
• Key saturation and recovery parameters of the SESAMs remain unaffected by the new fabrication method.

Conclusions:

• The choice of contacting technique is critical for managing thermal effects in high-power SESAMs.
• Novel substrate-transfer direct bonding offers a pathway to highly stable, large-area SESAMs for demanding laser applications.
• These advanced SESAMs are enabling components for future kilowatt-level ultrafast laser oscillators.