A Bessel Lens with a Flat Lens Unveils Technology that Creates a Nondiffracting Bottle Laser

Key Takeaways

• Binary axicon converts Gaussian to modified Bessel beam.
• Flat multilevel diffractive lens creates micron‑scale bottle beam.
• Beam remains nondiffracting over >20 cm propagation.
• Setup is compact, alignment‑free compared to traditional methods.
• Enables high‑harmonic generation and particle trapping applications.

Summary

Researchers at Chiba University have demonstrated a compact method to generate nondiffracting optical bottle beams using a binary axicon and a flat multilevel diffractive lens (MDL). The system reshapes a Gaussian beam into a modified zero‑order Bessel beam, which the MDL focuses into a micron‑scale bottle beam that maintains its shape over distances beyond 20 cm. This approach eliminates the complex, alignment‑intensive setups typically required for Bessel or bottle beam generation. The technique is compatible with ultrafast lasers and could support high‑harmonic generation and advanced particle manipulation.

Pulse Analysis

Structured light has become a cornerstone of modern photonics, offering the ability to tailor beam amplitude, phase, and polarization for specialized tasks. Traditional Gaussian beams spread quickly, limiting their utility in long‑range applications, while ideal Bessel beams, though nondiffracting, require intricate ring patterns that are difficult to implement. The emergence of optical bottle beams—three‑dimensional light cages—promised particle confinement but suffered from bulky, alignment‑sensitive optics. This backdrop sets the stage for a breakthrough that merges simplicity with performance.

The Chiba University team’s innovation hinges on two inexpensive components: a binary axicon and a flat multilevel diffractive lens. The axicon reshapes an incoming Gaussian beam into a modified zero‑order Bessel profile with suppressed sidelobes, mitigating the ring‑artifact issue that plagues conventional Bessel generation. The MDL, engineered via inverse design, then focuses this beam into a sharply defined, micron‑sized bottle structure that self‑heals and remains nondiffracting for more than 20 cm. Compared with conventional refractive lenses, the flat MDL delivers higher diffraction efficiency and precise longitudinal interference control, all within a compact, alignment‑free package.

Beyond the laboratory, this technology unlocks new possibilities for high‑harmonic generation, where intense, well‑controlled beams are essential, and for real‑time biological imaging in scattering media, where a stable light cage can probe deeper without distortion. The reduced footprint and cost lower barriers for industrial adoption in micromachining and optical tweezing, potentially accelerating market growth in precision manufacturing and quantum‑technology platforms. As ultrafast laser systems become more accessible, the integration of such compact nondiffracting bottle beams could become a standard tool in next‑generation photonic applications.