Ionic Liquid Gated Carbon Nanotube Saturable Absorber for Switchable Pulse Generation

Area of Science:

• Photonics
• Materials Science
• Optoelectronics

Background:

• Electrically tunable optical properties are crucial for advanced photonic applications.
• Single-walled carbon nanotubes (SWCNTs) exhibit optical property modulation in the near-infrared via electrochemical doping.
• Doping-induced changes in state filling affect both optical absorption and nonlinear optical response.

Purpose of the Study:

• To investigate the effect of electrochemical doping on the nonlinear optical absorption of SWCNT films.
• To demonstrate the application of tunable nonlinear absorption in controlling pulsed fiber laser generation.
• To explore the potential of SWCNTs in developing novel optical devices with adjustable nonlinearity.

Main Methods:

• Utilized a pump-probe technique to analyze the photobleaching and photoinduced absorption of SWCNT films under varying applied voltages.
• Fabricated a fiber laser incorporating a side-polished fiber with an integrated carbon nanotube electrochemical cell.
• Implemented gate voltage control to tune the absorption saturation within the fiber laser cavity.

Main Results:

• Demonstrated that electrochemical doping, with voltages below 2 V, can gradually reduce photobleaching and induce photoinduced absorption in SWCNTs.
• Successfully tuned the absorption saturation of the SWCNT saturable absorber within a fiber laser.
• Achieved reversible switching between femtosecond mode-locking and microsecond Q-switching regimes by adjusting gate voltages.

Conclusions:

• Electrochemical doping provides an effective method to tailor the nonlinear optical absorption of SWCNT films.
• The developed carbon nanotube electrochemical cell is a viable component for controlling pulsed fiber laser dynamics.
• This work presents a promising pathway for creating carbon nanotube-based optical devices with tunable nonlinear properties.