Structured light – electromagnetic waves with a strong spatial inhomogeneity of amplitude, phase, and polarization – has occupied far-reaching positions in both optical research and applications. Terahertz (THz) waves, due to recent innovations in photonics and nanotechnology, became so robust that it was not only implemented in a wide variety of applications such as communications, spectroscopic analysis, and non-destructive imaging, but also served as a low-cost and easily implementable experimental platform for novel concept illustration. In this work, we show that structured nonparaxial THz light in the form of Airy, Bessel, and Gaussian beams can be generated in a compact way using exclusively silicon diffractive optics prepared by femtosecond laser ablation technology. The accelerating nature of the generated structured light is demonstrated via THz imaging of objects partially obscured by an opaque beam block. Unlike conventional paraxial approaches, when a combination of a lens and a cubic phase (or amplitude) mask creates a nondiffracting Airy beam, we demonstrate simultaneous lensless nonparaxial THz Airy beam generation and its application in imaging system. Images of single objects, imaging with a controllable placed obstacle, and imaging of stacked graphene layers are presented, revealing hence potential of the approach to inspect quality of 2D materials. Structured nonparaxial THz illumination is investigated both theoretically and experimentally with appropriate extensive benchmarks. The structured THz illumination consistently outperforms the conventional one in resolution and contrast, thus opening new frontiers of structured light applications in imaging and inverse scattering problems, as it enables sophisticated estimates of optical properties of the investigated structures.

Invariant Bessel–Gauss beams have attracted great interest for transparent material microprocessing applications. The small central peak and elongated focal region of the zeroth-order Bessel–Gauss beam provide advantages in laser micromachining. However, many transparent material processing applications need asymmetric beams to induce directional cracking. Therefore, in this work, we investigate analytically, numerically, and experimentally a beam that was generated by spatially displaced axicon halves, which induces noncylindrical symmetry in the beam phase profile. Analytical solutions were found and verified experimentally. High power and quality beams were generated by writing a needed phase alteration of the beam with a geometric phase element. These beams were able to demonstrate applicability to micromachine processing of transparent material.

The art of light engineering unveils a world of possibilities through the meticulous manipulation of photonic properties such as intensity, phase, and polarization. Precision control over these properties finds application in a variety of fields spanning communications, light–matter interactions, laser direct writing, and imaging. Terahertz (THz) range, nestled between microwaves and infrared light, stands out for its remarkable ability to propagate with minimal losses in numerous dielectric materials and compounds, making THz imaging a powerful tool for noninvasive control and inspection. In this study, a rational framework for the design and optimal assembly of nonparaxial THz imaging systems is established. The research is centered on lensless photonic systems composed solely of high‐resistivity silicon‐based nonparaxial elements such as the Fresnel zone plate, the Fibonacci lens, the Bessel axicon, and the Airy zone plate, all fabricated using laser ablation technology. Through a comprehensive examination through illumination engineering and scattered light collection from raster‐scanned samples in a single‐pixel detector scheme, the imaging systems are evaluated via diverse metrics including contrast, resolution, depth of field, and focus. These findings chart an exciting course toward the development of compact and user‐friendly THz imaging systems where sensors and optical elements seamlessly integrate into a single chip.

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.