Faculty members of the Center for Terahertz Research are among the world's first scientists to exploit the unique advantages of terahertz (THz) radiation. Using the relatively unexplored terahertz portion of the electromagnetic spectrum, they are creating innovative imaging and sensing technologies that hold enormous potential in biomedical imaging, genetics diagnostics, microelectronics, and the chemical and biological materials identification fields.

The promise of terahertz wave radiation, known as "T-rays," is being realized through ongoing research at the THz Center's four state-of-the-art laboratories: Xi-Cheng Zhang's THz Optoelectronics lab, Michael Shur's THz Electronics lab, Roland Kersting's THz Quantum Optics lab, and Ingrid Wilke's THz Spectroscopy lab. Together, these researchers are overcoming significant challenges posed by the lack of understanding of the fundamental physics that underlie this large – and historically inaccessible – portion of the electromagnetic spectrum.

Rensselaer's THz research faculty is the established leader in the development and application of terahertz technology. Their breakthroughs in developing electro-optic THz emitters and detectors have opened the door to tremendous sensing and imaging opportunities for academic and industrial applications and earned them six patents with another several pending.

Next Rays? T-rays!
Scientists are drawn to this elusive portion of the electromagnetic spectrum, which lies between infrared and microwave bands, because of the advantages that T-rays offer over conventional imaging technologies. Unlike X-rays, T-rays can be focused and are capable of producing images with signature or fingerprint capability, also called functional imaging. T-rays' low photon energy levels allow the imaging of biological tissue without harmful ionizing radiation, making them safer than X-rays. And the unique vibrational, rotational, and translational responses of materials within the THz range provide information generally absent in optical, X-ray and NMR images, enabling a sort of THz wave fingerprint of the molecular structure of the material being imaged. This fingerprinting will allow T-rays to one day be used to detect harmful biological or chemical agents.

Closing the Terahertz Gap
Shur and Kersting are among the first scientists in the world to create prototype devices for systems that use terahertz waves to carry microelectric signals. Their pioneering research with terahertz-speed electronic devices has been credited with closing the "terahertz gap" – the term for the scientifically rich but technologically undeveloped THz frequency. Wilke pioneered the application of single-shot THz-radiation pulse measurements to femtosecond relativistic electron beam bunch length measurements. This is a significant advancement of electron beam diagnostics for new types of x-ray free electron laser and high energy physics.

Research at the center is currently focused on the generation and detection of free-space THz beams using ultra-fast optics and electro-optic crystals. A primary goal is to develop and refine the instrumentation – finding higher dynamic ranges, achieving faster data acquisition, and increasing sensitivities to enable the detection of monomolecular layers – that will move THz technology beyond its current niche applications to support wider use in biomedicine.

Rays of Hope – Biomedicine
Perhaps the greatest potential for this research lies in biomedical imaging and genetic diagnostics. T-rays offer hope for improved detection of breast cancer through sharper imaging and molecular fingerprinting. Each year, more than a half million biopsies of breast tissue are required to compensate for inaccurate and uncertain diagnoses using current detection methods. Zhang has begun working with doctors at the Boston Medical Center, using THz systems developed at Rensselaer to identify breast tumors. Another medical research team in England has received a grant of $6 million to perform clinical studies using the technology developed here. Nikon in Japan has developed a commercial T-ray imaging system based on Rensselaer's invention.

Rensselaer's terahertz research group has received nearly $10 million in grants from the National Science Foundation, Army Research Office, Army Research Laboratory, Air Force Office of Scientific Research, Defense Advanced Research Projects Agency, Department of Energy, Research Corporation, IMRA America Incorporated, Molecular OptoElectronic Corporation, and Zomega Technology Corporation.

Terahertz – Waves of the Future
The center's four labs are equipped with the most advanced photonic and opto-electronic instrumentation for generating, measuring, and recording picosecond and femtosecond terahertz radiation waves. The research center currently supports four faculty members and at least 30 graduate and 30 undergraduate students.

Rensselaer's Center for Terahertz Research stands at the forefront of terahertz technology, a science still in its infancy yet expected to become one of the most promising research areas for transformational imaging in the 21st century.