Laser-micromachined zebra-patterned graphene as a mode locker with adjustable loss

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Saturable absorbers are crucial for initiating ultrashort pulse generation in lasers.
• Graphene's unique optical properties make it a promising material for saturable absorbers.
• Achieving adjustable loss in saturable absorbers is key to optimizing laser performance.

Purpose of the Study:

• To introduce a novel micro-structured graphene saturable absorber, termed zebra-patterned graphene saturable absorber (ZeGSA).
• To demonstrate ZeGSA's capability for initiating femtosecond pulse generation with adjustable loss.
• To evaluate the performance of ZeGSA in a Cr4+:forsterite laser system.

Main Methods:

• Fabrication of ZeGSA using femtosecond laser micro-machining to ablate monolayer graphene on an infrasil substrate.
• Creating stripe patterns with varying duty cycles to achieve insertion loss in the range of 0.21%-3.12%.
• Testing the mode-locking performance of ZeGSA in a Cr4+:forsterite laser operating near 1250 nm.

Main Results:

• ZeGSA enabled successful mode-locking in a Cr4+:forsterite laser.
• Mode-locked output power increased from 68 mW to 114 mW compared to non-ablated graphene.
• Pulse duration decreased from 62 fs to 48 fs at the same incident pump power.
• Demonstrated adjustable loss functionality of the ZeGSA device.

Conclusions:

• ZeGSA is a novel saturable absorber with adjustable loss for femtosecond pulse generation.
• The device significantly improved power performance and reduced pulse duration in a Cr4+:forsterite laser.
• ZeGSA shows great potential for applications in developing femtosecond lasers across a broad spectral range.