Mid-infrared pulsed Er:ZBLAN fiber laser producing mode-switchable cylindrical vector beams

Area of Science:

• Optics and Photonics
• Laser Physics
• Materials Science

Background:

• Cylindrical vector beams (CVBs) offer unique polarization properties crucial for advanced optical applications.
• Mid-infrared (MIR) lasers are gaining importance in fields like biomedicine and material processing.
• Generating MIR CVBs efficiently and with switchable polarization remains a challenge.

Purpose of the Study:

• To demonstrate the generation of continuous-wave (CW) and Q-switched CVBs in the mid-infrared region.
• To achieve switchable radial and azimuthal polarization states in the generated MIR CVBs.
• To explore the potential of Er³⁺-doped ZBLAN fiber lasers for producing these specialized beams.

Main Methods:

• Utilized an Er³⁺-doped ZBLAN fiber laser operating at approximately 2.8 µm.
• Incorporated a customized S-waveplate as an intracavity mode converter to generate CVBs.
• Manipulated cavity conditions to achieve switchable radial and azimuthal polarization modes.

Main Results:

• Successfully generated both continuous-wave (CW) and Q-switched mid-infrared CVBs.
• Achieved a maximum output power of approximately 250 mW for CW CVBs.
• Demonstrated Q-switched operation with pulse durations in the hundreds of nanoseconds, realized through both active and passive Q-switching modes.

Conclusions:

• The developed mid-infrared fiber laser system effectively generates switchable cylindrical vector beams.
• The system offers both CW and pulsed operation modes, expanding its versatility.
• These MIR CVBs hold significant potential for applications in biomedicine, optical trapping, material processing, and optical communication.