Developing carbon-nitride nanosheets for mode-locking ytterbium fiber lasers

Area of Science:

• Materials Science
• Optoelectronics
• Laser Physics

Background:

• Graphitic carbon nitrides (CNs) are emerging as photocatalysts for water splitting.
• The nonlinear optical properties, specifically saturable absorption, of CNs remain largely unexplored.
• Saturable absorbers are crucial components for passive mode-locking in lasers.

Purpose of the Study:

• To investigate the saturable absorption effects of novel 2D carbon-nitride-type nanosheets.
• To utilize these CN nanosheets as saturable absorbers for passively mode-locking Yb-doped fiber lasers.
• To explore the potential of CNs in photonic and optoelectronic applications.

Main Methods:

• Fabrication of a CN-based saturable absorber by solution coating 2D CN nanosheets on a gold mirror.
• Characterization of the saturable absorber's modulation depth (12.5%) and saturation intensity (7.5 MW/cm²).
• Construction of ring laser cavities using two different output couplers (10% and 50%) to test laser performance.

Main Results:

• A 10% output coupler yielded a mode-locked fiber laser with ~310 ps pulse duration, 1.24 mW average power, and 7.65 MHz repetition rate at 1066 nm.
• A 50% output coupler increased output power to 2.58 mW but broadened the pulse width to 420 ps.
• The laser spectrum showed a bandwidth of 2.4 nm centered at 1066 nm.

Conclusions:

• 2D carbon nitride nanosheets demonstrate significant saturable absorption properties.
• CN-based saturable absorbers are effective for passively mode-locking Yb-doped fiber lasers.
• These findings suggest a promising new class of 2D materials for advanced photonic and optoelectronic devices.