Structured light—electromagnetic waves with spatial inhomogeneity of amplitude, phase, and polarization—because of its fascinating ability to precisely control these properties, has garnered significant attention across various research fields. Particular interest is given to developing imaging systems where the requirement to increase image resolution, contrast, and ability to resolve tiny structures is of utmost importance. This task can be achieved well using single-shot imaging; however, it remains challenging to implement in conventional terahertz (THz) imaging systems using Gaussian modes. A single-pixel imaging scheme is more attractive for implementation in real operational conditions as it employs sophisticated schemes with single-pixel detectors to retrieve images. It was very recently determined that structured light illumination and image collection schemes are beneficial for various metrics in single-pixel THz imaging [S. Orlov et al., Laser Photonics Rev. 18, 2301197 (2024)]. This work introduces angular momentum in structured light illumination for THz image retrieval, demonstrating simultaneous enhancement of object edge detection while maintaining resolution and contrast. We investigated three experimental approaches at 253 GHz: a nonparaxial Fresnel zone plate, a THz vortex with a zone plate, and a THz Bessel beam with a vortex. The diffractive optical elements were fabricated by 3D laser printing, while silicon-based diffractive elements were prepared by laser ablation technology. Through comprehensive experimental studies supported by numerical modeling, we reveal distinct features of structured THz light induced by angular momentum. This approach establishes a new pathway for developing advanced single-pixel THz imaging systems that leverage the angular momentum of structured light, offering the foundation for future improvements in performance via enhanced edge detection and extended material characterization capabilities.

Carbon-fiber-reinforced plastic (CFRP) is a popular material possessing great properties, such as strength, lightness, and resistance to corrosion and the environment. Important steps in the production of various parts made of CFRP are surface structuring, milling, drilling and cutting processes. Here, we propose to use ultrashort pulse lasers to achieve the high-quality, low-heat-affected-zone ablation of CFRP. We investigated the ablation efficiency dependence on the processing parameters, such as the pulse duration, pulse energy and pulse overlap. We showed that good-quality results could be achieved using just low-/mid-average-power femtosecond laser equipment. We also discuss further cutting process optimization possibilities using ultrashort pulse lasers and show the possibility of HAZ-free CFRP cutting by femtosecond laser ablation.

We propose a method for creating parallel Bessel-like vortical optical needles with an arbitrary axial intensity distribution via the superposition of different cone-angle Bessel vortices. We analyzed the interplay between the separation of individual optical vortical needles and their respective lengths and introduce a super-Gaussian function as their axial profile. We also analyzed the physical limitations to observe well-separated optical needles, as they are influenced by the mutual interference of the individual beams. To verify our theoretical and numerical results, we generated controllable spatial arrays of individual Bessel beams with various numbers and spatial separations by altering the spectrum of the incoming laser beam via the spatial light modulator. We demonstrate experimentally how to implement such beams using a diffractive mask. The presented method facilitates the creation of diverse spatial intensity distributions in three dimensions, potentially finding applications in specific microfabrication tasks or other contexts. These beams may have benefits in laser material processing applications such as nanochannel machining, glass via production, modification of glass refractive indices, and glass dicing.