Page 21 - Spring 2025 Electron

Industry News Industry News

NEW CHIP-BASED

SYSTEM FOR TERAHERTZ

WAVE GENERATION

NEW PHOTONIC CHIP

REVOLUTIONISES OPTICAL

AMPLIFIER PERFORMANCE

The effective generation of Terahertz waves using The thin sheet utilises ‘matching’, which equals
a semiconductor chip is known to be challenging. out the dielectric constants of silicon and air,
Many current technologies are unable to generate minimising the amount of signal that is reflected at
waves with sufficient radiating power without the the boundary. It consists of a low-cost, commercially
use of bulky and expensive silicon lenses, which available substrate with a dielectric constant that
greatly restricts integration of a terahertz source approximates to what is needed for the match. A
into an electronic device. laser cutter was then used to punch holes in the
sheet until it reached the correct dielectric constant.
Scientists at Ecole Polytechnique Federale de waves reinforce each other, enhancing weak signals Terahertz waves, which occupy a position between
Special Intel transistors were then applied with a
Lausanne and IBM Research have developed a and maintaining a low noise level. radio waves and infrared light, have shorter
compact optical amplifier based on a revolutionary wavelengths and higher frequencies than radio higher maximum frequency and breakdown voltage
The TWPA was also found to enhance performance than standard CMOS transistors.
photonic chip which is said to “vastly outperform” waves meaning that they can enable faster data
of optical frequency combs and coherent
traditional optical amplifiers in terms of both transmission, more precise medical imaging and The resultant chip-generated terahertz signals
communication signals, two important technologies
bandwidth and efficiency with potential higher resolution radar. Unfortunately, however, achieved a peak radiation power of 11.1 decibel-
in modern optical networks and photonics,
implications for data centre interconnects, AI the dielectric constant of silicon is much higher milliwatts.
demonstrating that such photonic integrated circuits
accelerators and high performance computing. than that of air, resulting in most terahertz waves
can outperform traditional fibre-based amplification Jinchen Wang, graduate student at the MIT
being reflected at the silicon-air boundary rather
The photonic-chip-based travelling-wave systems. Department of Electrical Engineering and Computer
than being transmitted. With most signal strength
parametric amplifier, or TWPA, achieves ultra- Science, explains:
Reference: Dykes, P., ‘Ultra-broadband Photonic Chip boosts Optical being lost at this boundary, silicon lenses have to
broadband signal amplification in a highly compact Signals’, Optical Connections News, 25th. March
be installed to increase the power of the remaining “ To take full advantage of a terahertz wave
form. Using gallium on phosphide-on-silicon dioxide
signal. source, we need it to be scalable. A terahertz
technology, it attains a net gain of over 10dB across
array might have hundreds of chips, and there is
a bandwidth of approximately 140nm, which is three In order to address this limitation, researchers at the
no place to put silicon lenses because the chips
times wider than a conventional C-band EDFA. Massachusetts Institute of Technology (MIT) have
are combined with such high density. We need a
developed a scalable, low-cost terahertz amplifier-
Gallium phosphide is noted for its exceptional optical different package, and here we’ve demonstrated a
multiplier system that can generate high-power
properties, namely strong optical connectivity, such promising approach that can be used for scalable,
terahertz waves on a chip without the need for silicon
that light passing through it can interact in a way that low-cost terahertz arrays.
lenses.
boosts signal strength, and a high refractive index,
Since the dielectric constant of air is 1, if you just
which allows light to be confined tightly within the By attaching a thin, patterned sheet of material to
cut some subwavelength holes in the sheet, it is
waveguide leading to more efficient amplification. the back of the chip and using higher-power Intel
This meant that the team could achieve high gain transistors, the researchers created a more efficient, equivalent to injecting some air, which lowers the
overall dielectric constant of the matching sheet.
with a waveguide that was relatively short, only a few yet scalable, chip-based terahertz wave generator.
centimetres. The said chip can then be used to produce terahertz Because the frequency and the power are so high,
arrays for applications such as improved safety many of the standard ways to design a CMOS chip
Whilst most amplifiers rely on rare earth elements
scanners and environmental monitoring, eg. for are not applicable here.”
to strengthen signals, the TWPA uses optical non-
detection of airborne pollutants.
linearity whereby light interacts with a material Reference: Gittins, C., ‘MIT Researchers develop Chip-based System
for Terahertz Waves’, Electronic Specifier, 3rd. March
and amplifies itself. Careful design of the tiny spiral
waveguide enabled creation of a space in which light
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