Planar Porous Components for Low‐Loss Terahertz Optics

Abstract

There is a strong interest in using the terahertz (THz) frequency band for applications in sensing, imaging, and wireless communications. To enable many of these applications, compact low‐loss components for beamforming are required. Typically, such components are made using solid dielectric elements with spatially variable thickness, for example, planoconvex lenses or spiral phase plates. However, as losses in dielectrics typically greatly increase with THz frequency, so do the losses of the solid components. This work demonstrates that when introducing low‐refractive index, low‐loss subwavelength inclusions (air holes) into a solid material matrix, the loss of porous components can be greatly reduced compared to the loss of solid components with otherwise identical optical properties, thus opening a way to create efficient optical components even with nominally high‐loss materials. Additionally, porous optical components can be created completely flat as spatially dependent optical path difference is achieved by varying the local porosity rather than the component thickness. This offers additional advantages for free‐space alignment and integration of such components into optical systems. As an example, the design, fabrication, and experimental characterization of planar lenses and planar orbital angular momentum phase plates are carried out. It is then demonstrated how these porous components outperform their all‐solid counterparts.

Cellular effects of terahertz waves

“…Being adequately studied and regulated, such a versatile impact of THz waves on living cell opens a variety of THz technology applications in medical therapy of cancers, inflammatory, and neurodegenerative deceases. Finally, we notice that development of such THz therapeutic applications would require further progress in THz components, including highly efficient uncooled CW and pulsed THz emitters, 6 , 7 , 126 – 128 , 130 , 132 – 135 elements of bulk (open space) and fiber/waveguide optics 293 – 299 aimed at the THz-wave delivery to the hardly accessible tissues and internal organs. Such elements are still to be developed.…”

Terahertz technology in intraoperative neurodiagnostics: A review

“…Detection and resection of brain tissue infiltrated with these cells is a critical task, aimed at increasing the surgical treatment radicality and improv- J o u r n a l P r e -p r o o f ing the patient's survival. At the moment, such features of the tumor cell-population composition can be detected only by the single-cell sequencing, that remains extremely expensive and inapplicable in the intraoperative conditions 197 . The development of new tools for the intraoperative cell-population mapping in brain tissue based on the THz microscopy principles is an extremely important fundamental and clinical task.…”

3D Printed Sub-Terahertz All-Dielectric Lens for Arbitrary Manipulation of Quasi-Nondiffractive Orbital Angular Momentum Waves

“…For OAM based wireless communication systems, it is essential to generate electromagnetic waves (EMWs) carrying OAM efficiently. In the THz regime, there are several technologies to produce OAM beams, including metamaterial, metasurfaces, − half-wave phase plates, , and lenses. , Nevertheless, OAM based THz wireless communication systems still face some challenges in practical applications. With respect to multiple-input multiple-output (MIMO) systems, OAM communication systems can increase the channel capacity in a point-to-point link more effectively since they employ the new degree of freedom provided by OAM to create multiple independent channels at a single frequency .…”