Mode-filtered large-core fiber for short-pulse delivery with reduced nonlinear effects

Area of Science:

• Optics and Photonics
• Fiber Optics Engineering
• Nonlinear Optics

Background:

• High-power ultrashort pulse delivery often requires specialized fiber optics.
• Large-core fibers (LCFs) offer high energy transmission but typically support multiple modes.
• Maintaining single-mode beam quality in LCFs for intense pulses is challenging.

Purpose of the Study:

• To develop a large-core fiber (LCF) capable of single-mode delivery of intense ultrashort laser pulses.
• To reduce nonlinear effects in the fiber for high-power applications.
• To create a flexible delivery medium for specialized optical systems.

Main Methods:

• Fabrication of a tapered-fiber mode filter within an LCF.
• Gradual reduction of the LCF core diameter from 20 µm to 6 µm at the waist.
• Immersion of the tapered region in an index-matched liquid to suppress higher-order modes.

Main Results:

• The mode-filtered LCF effectively rejected higher-order modes, achieving single-mode operation.
• The fiber demonstrated reduced nonlinear properties suitable for intense pulse delivery.
• The LCF maintained its single-mode characteristics despite the original multimode nature of the fiber.

Conclusions:

• The developed mode-filtered LCF provides a viable solution for single-mode ultrashort pulse delivery.
• This fiber technology is well-suited for applications requiring flexible, short-distance (<4 m) beam transmission.
• Potential applications include endoscopic multiphoton microscopy and other high-intensity optical systems.