White light Bessel-like beams generated by miniature all-fiber device

Area of Science:

• Optics and Photonics
• Fiber Optics
• Beam Propagation

Background:

• Generating non-diffracting beams, such as Bessel beams, is crucial for various optical applications.
• Traditional methods often require complex setups or specific light sources.
• Achieving non-diffracting white light propagation with inherent spatial coherence has been a challenge.

Purpose of the Study:

• To present a simple and compact all-fiber device for generating micron-sized, white light propagation invariant beams.
• To demonstrate a novel method for creating non-diffracting white light beams using a broadband light source.
• To investigate the influence of multimode fiber core size on beam propagation distance.

Main Methods:

• Fabrication of an all-fiber device by splicing a large-core multimode fiber (MMF) onto a single-mode fiber (SMF).
• Utilizing a temporally incoherent broadband light source (halogen bulb) for white light generation.
• Testing MMFs with core diameters of 50 μm, 105 μm, and 200 μm.

Main Results:

• Successful generation of micron-sized, white light Bessel-like beams.
• Demonstrated non-fading surrounding fringes with increasing light source bandwidth, distinct from axicon-based methods.
• Observed that the non-diffracting propagation distance increases with larger MMF core sizes.
• Characterized the propagation of individual red, green, and blue light components.

Conclusions:

• The developed compact fiber device offers a straightforward approach to generating white light propagation invariant beams.
• This method provides inherent spatial coherence, enabling non-diffracting white light propagation from broadband sources.
• The device's performance, particularly propagation distance, is scalable with the multimode fiber core diameter.