Exploring the Frontiers of Optical and Laser Sciences
Generating nondiffracting bottle Beams with a flat multilevel diffractive lens
We introduce a novel method for generating a high-quality, sharply defined, nondiffracting optical bottle beam by focusing a Bessel beam propagating through a flat multilevel diffractive lens (MDL). This study highlights the impact of the MDL illuminated by a Bessel beam with suppressed sidelobes generated from a binary axicon. The resulting Bessel bottle beam exhibits a series of low- or zero-intensity zones interleaved with high-intensity regions, with periods ranging from 0.2 to 1.36 mm along the beam propagation direction. The transverse intensity profiles of these regions remain shape-invariant over long distances in free space, and thereby, the nondiffracting range of the micron-sized optical bottle beam exceeds 5 cm. We also observe that the far-field output from the MDL, when illuminated by a Bessel beam, offers advantages over that of conventional focusing lenses. Furthermore, this technique can operate on ultrafast time scales (from pico- to femtoseconds) due to the high damage thresholds of the binary axicon and MDL, enabling the generation of high-power optical bottle beams. Ultimately, our experimental approach paves the way for various applications, including high-resolution biological imaging in turbid media, particle manipulation, micromachining, and harmonic generation, by leveraging the spatial landscape of the optical bottle beam.
18-02-2026 Read MoreGenerating high-harmonic array beams
The demand for spatially structured ultrashort beams at shorter wavelengths is high, and their adaptability in potential applications such as imaging, metrology, and attosecond science is undeniable. In this work, we present the generation of high-harmonic array beams. We utilize ultrashort structured array beams in the near-infrared wavelength as the pump source to reliably generate extreme-ultraviolet array beams at the tenth harmonic of the pump wavelength. The pump array beams showed shape-invariant free space propagation and exhibited a self-healing ability against adverse spatial effects introduced by aberrations. Moreover, we found that the spatial profile of these array beams remained unchanged for any polarization state, a unique feature that enhances their versatility. The interaction of shape-invariant array beams with an argon gas jet in a two-color pump configuration generated high harmonics consisting of both weak odd and even orders, a suppression of odd harmonics from the 13th to the 17th order when driven by two-color laser fields, but a strong 10th order harmonic appeared in the extreme-ultraviolet. This 10th harmonic unveiled a spatial distribution, including a unique string structure that is a hallmark of array beams. This extreme nonlinear optical process of structured high-harmonic generation is a significant advancement that offers a new degree of freedom for generating diverse structured harmonics in extreme ultraviolet and soft x-ray regimes.
13-02-2025 Read More