The electromagnetic spectrum holds vast potential for technological advancements, and researchers from Rice University have recently discovered a previously unexplored portion of this spectrum. While visible light has been extensively studied, frequencies beyond human vision have largely remained untapped. This untapped area, commonly referred to as the “new terahertz gap,” encompasses frequencies of 5-15 terahertz and wavelengths ranging from 20-60 micrometers. In comparison to higher optical frequencies and lower radio frequencies, this gap lacks commercial products. Despite this challenge, the Emerging Quantum and Ultrafast Materials Laboratory at Rice University has developed a groundbreaking solution.
Challenges in the Terahertz Frequency Region
Exploring the terahertz frequency region presents scientists with several obstacles, including the shortage of suitable materials for carrying and processing light waves. Most available materials within this range strongly interact with light, resulting in rapid absorption. However, under the leadership of Hanyu Zhu, an assistant professor of materials science and nanoengineering, the research team has made an exciting discovery using strontium titanate.
Strontium titanate, an oxide composed of strontium and titanium, exhibits a distinctive property called quantum paraelectricity. This property allows the atoms of the material to couple with terahertz light, forming new particles referred to as phonon-polaritons. Unlike other materials that only support phonon-polaritons within a narrow frequency range, strontium titanate enables these particles to exist throughout the entire 5-15 terahertz gap. Furthermore, these phonon-polaritons are confined to the surface of the material, eliminating the risk of loss.
Through the development and fabrication of ultrafast field concentrators, the researchers successfully demonstrated the concept of strontium titanate phonon-polariton devices within the frequency range of 7-13 terahertz. These devices compress light pulses into volumes smaller than their wavelengths, thus preserving their short durations. Consequently, this compression generates a powerful transient electric field, reaching nearly a gigavolt per meter. Such an influential electric field allows for the alteration of material structures, creating new electronic properties. Additionally, it can produce a new nonlinear optical response from trace amounts of specific molecules, which can be detected using a standard optical microscope.
The innovative design and fabrication methodology developed by Zhu’s group have broad applicability, extending to numerous commercially available materials. This breakthrough discovery holds the potential to enable the development of photonic devices within the range of 3-19 terahertz. The implications of this advancement are far-reaching and could significantly impact various fields, including quantum electronics and medical diagnosis.
Contributors and Collaborators
In addition to the lead authors, Rui Xu and Hanyu Zhu, several other contributors played vital roles in this research. Xiaotong Chen, a postdoctoral researcher in materials science and nanoengineering, as well as Elizabeth Blackert, Tong Lin, Jiaming Luo, Alyssa Moon, and Khalil JeBailey, all students at Rice University, contributed to this groundbreaking study.
The research conducted at Rice University has unlocked the vast potential of the “new terahertz gap” within the electromagnetic spectrum. Through the utilization of strontium titanate with its unique properties, researchers have opened new avenues for the development of photonic devices and the study of quantum materials. This discovery has promising implications for various fields, including quantum electronics and medical diagnosis. It serves as a testament to the continuous pursuit of knowledge and innovation in scientific research.