Packaging boosts terahertz sensor

Researchers at the Massachusetts Institute of Technology (MIT) in the United States have made a significant breakthrough in terahertz technology by developing a high-power amplifier-multiplier system using specialized transistors from Intel, all without the need for traditional silicon lenses.

By attaching a thin, patterned sheet of material to the back of the chip and utilizing Intel's high-power transistors, the team has created a scalable, chip-based terahertz wave generator that has the potential for various applications.

One of the key advantages of this innovation is the ability to create terahertz arrays, which could be used in security scanners to detect hidden objects or in environmental monitoring to identify airborne pollutants with precision.

Jinchen Wang, a graduate student in the Department of Electrical Engineering and Computer Science at MIT and the lead author of the research paper on the terahertz radiator, emphasized the importance of scalability in terahertz technology. Wang stated, "To take full advantage of a terahertz wave source, we need it to be scalable. A terahertz array might have hundreds of chips, and there is no place to put silicon lenses because the chips are combined with such high density."

The MIT researchers employed a matching technique to equalize the dielectric constants of silicon and air, reducing signal reflection at the boundary. The thin dielectric sheet on the back of the chip plays a crucial role in ensuring that most waves are transmitted out the back rather than being reflected.

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Furthermore, the team used a laser cutter to create tiny holes in the sheet, adjusting the dielectric constant until it was precisely calibrated. Wang explained, "Since the dielectric constant of air is 1, if you just cut some subwavelength holes in the sheet, it is equivalent to injecting some air, which lowers the overall dielectric constant of the matching sheet."

The Intel terahertz transistors, initially introduced in 2001 at the IEDM conference, leverage silicon in insulator and specialized materials to achieve a higher maximum frequency and breakdown voltage compared to traditional CMOS transistors.

Wang highlighted the combined impact of the powerful transistors and the dielectric sheet, along with other innovations, in surpassing the performance of several other devices. The chip developed by the team was capable of generating terahertz signals with a peak radiation power of 11.1 dBmW and is poised for integration into practical electronic devices.

Looking ahead, the researchers aim to construct a phased array of terahertz sources, enabling the steering and focusing of a potent terahertz beam using a cost-effective, compact device.

The research received support from NASA's Jet Propulsion Laboratory, the Strategic University Research Partnerships Programme, and the MIT Centre for Integrated Circuits and Systems. The chip fabrication was made possible through the Intel University Shuttle Programme.