Physics Dept Seminar

February 1, Thursday (*SPECIAL DAY*)

Meta-Structures for Terahertz Technologies

Dr. Subhajit Karmakar

Princeton Univ.

(Optics, Host: Benjamin Thomas)

*Special Time: 10:15am-11:15am with 10am teatime

*Room: 407 Tiernan (** SPECIAL ROOM **)

The terahertz (THz) radiation (frequency ranges between 0.1 to 10 THz broadly, commonly termed as ‘THz Gap’) has drawn significant research attention over the past decades that explores the properties of both millimeter wave and infrared radiation. Terahertz radiation is non-ionizing, non-destructive to living creatures, and provides more functional bandwidth than traditionally employed millimeter waves for next-generation wireless technologies. Hence, terahertz technology is often regarded as a promising avenue to provide technological solutions related to security, imaging, non-destructive evaluation, food waste, health monitoring, high-speed wireless technology, and ultrafast spintronics, etc. Recently, terahertz is also recognized as a driving force for the 6G and beyond communications. Despite these facts, terahertz technologies have yet to explore their potential due to weak terahertz–matter interactions and a lack of efficient functional components in this regime. In this context, electromagnetic meta-structures are believed to address these technological challenges for various terahertz applications. Meta-structures (in other words, Metamaterials, ‘beyond the natural materials or structures’) are artificially engineered subwavelength structures that were conceived to realize several unusual and exceptional properties that were not viable earlier. Meta-structures garner merit from their geometrical designs, irrespective of the constructive materials.

This talk will introduce a general technological outlook to design meta-structures for the terahertz domain. Imperative of the diverse functionalities of metamaterial-based structures, their efficiency is limited due to their associated losses. The dominant loss contributor is radiative loss. To tackle such losses, this talk will introduce various design principles of non-radiative metamaterials for the terahertz domain. The concept of metamaterial-based cavities (stacked meta-structures) will also be discussed to excite Fano resonances in structurally symmetric resonators. Fano resonant cavities enhance energy confinement in the deep-subwavelength scale and realize highly sensitive (> 1 THz/ RIU) terahertz non-destructive sensors. This talk will also introduce the concept of terahertz magnetic wire, terahertz magnetospectroscopy, and spintronic metamaterials. Spintronic meta-structures demonstrated huge potential to realize low-power (a few mT) magnetic sensors, applicable at the terahertz regime. The later part of the talk will describe how a sub-terahertz metamaterial-based sticker can address real-world food waste problems and provide a narrowband solution applicable to 6G mobile technologies. Finally, a full-duplex beamforming strategy at the sub-terahertz regime will also be discussed by integrated leaky-wave architecture in the context of 6G communication. In summary, this talk will cover a few contemporary research directions on meta-structures that exemplify their ability to be utilized in terahertz non-destructive sensing, enhanced spectroscopy, photonics, spintronics, and communication.