Surreal illustration of terahertz waves manipulating a croconic acid molecule for ultrafast data transmission.

Can Terahertz Fields Unlock the Future of High-Speed Communications?

Soraya Malik in Tech & Innovation June 2025 • 4 min read.

"Scientists achieve ultrafast polarization control using terahertz fields, paving the way for advanced optical modulation and faster data transmission."

In the quest for faster and more efficient communication technologies, scientists are constantly exploring new ways to manipulate light. One promising avenue involves using electric fields to control the polarization of certain materials known as ferroelectrics. Rapid polarization control is crucial for high-frequency modulation of light, which is essential for optical communications. This has the potential to revolutionize how we transmit data, enabling faster internet speeds and more efficient data centers.

A study published in Scientific Reports explores the use of terahertz fields to achieve ultrafast polarization control in a hydrogen-bonded molecular ferroelectric called croconic acid. This research highlights the potential of using electronic polarization within molecules as a key strategy for manipulating these materials. Croconic acid is an organic compound that exhibits ferroelectricity, meaning it can maintain an electric polarization that can be reversed by applying an external electric field. What makes croconic acid particularly interesting is the role of its π-electrons, which are theorized to contribute significantly to its ferroelectric properties.

The researchers demonstrated that they could modulate the polarization of croconic acid on a sub-picosecond timescale using terahertz pulses. Terahertz radiation lies between microwaves and infrared light on the electromagnetic spectrum. It offers unique capabilities for manipulating materials at extremely high speeds. This breakthrough could lead to the development of new optical modulators that are significantly faster than current technologies.

How Does Terahertz Control Work?

Surreal illustration of terahertz waves manipulating a croconic acid molecule for ultrafast data transmission.

The research team used a combination of terahertz-pulse-pump second-harmonic-generation-probe and optical-reflectivity-probe spectroscopy to investigate the effects of terahertz pulses on croconic acid. These techniques allowed them to observe how the polarization of the material changed in response to the electric field. They discovered that the amplitude of polarization modulation reached 10% through electric-field-induced modifications of π-electron wavefunctions. This means the electric field from the terahertz pulse alters the distribution of electrons within the molecules, leading to a change in the material's polarization.

To understand the underlying mechanisms, the researchers also examined the changes in the infrared molecular vibrational spectrum caused by the electric field. This analysis revealed that the contribution of proton displacements to the polarization modulation was negligibly small. In simpler terms, the movement of protons within the molecules did not play a significant role in the observed polarization changes. This finding underscores the electronic nature of polarization in hydrogen-bonded molecular ferroelectrics like croconic acid.

Terahertz-Pulse-Pump SHG-Probe: Measures changes in second harmonic generation to detect polarization modulation.
Optical-Reflectivity-Probe Spectroscopy: Observes changes in how light is reflected to understand alterations in π-electron wavefunctions.
Infrared Molecular Vibrational Spectrum Analysis: Determines the contribution of proton displacements to the polarization modulation.

The results demonstrate that the polarization in croconic acid is primarily controlled by the π-electrons, which can be rapidly manipulated by terahertz fields. This electronic nature of polarization is what allows for the ultrafast control observed in the experiment. The ability to manipulate the electronic structure of a material with such precision opens up new possibilities for designing advanced electronic and optical devices.

The Future of Ultrafast Polarization Control

The ultrafast polarization control achieved through π-electron systems in croconic acid represents a significant step forward in the field of ferroelectrics. The researchers believe that this approach can be extended to other hydrogen-bonded molecular ferroelectrics, paving the way for future high-speed optical-modulation devices. As data transmission demands continue to grow, the need for faster and more efficient technologies will only intensify. Terahertz-based control of ferroelectric polarization offers a promising solution to meet these challenges and unlock new possibilities in optical communications and beyond.

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This article is based on research published under:

DOI-LINK: 10.1038/s41598-018-33076-9, Alternate LINK

Title: Ultrafast Polarization Control By Terahertz Fields Via Π-Electron Wavefunction Changes In Hydrogen-Bonded Molecular Ferroelectrics

Subject: Multidisciplinary

Journal: Scientific Reports

Publisher: Springer Science and Business Media LLC

Authors: T. Miyamoto, D. Hata, T. Morimoto, H. Yamakawa, N. Kida, T. Terashige, K. Iwano, H. Kishida, S. Horiuchi, H. Okamoto

Published: 2018-10-09

Everything You Need To Know

What exactly are terahertz fields, and why are they useful for controlling materials like croconic acid?

Terahertz fields are electromagnetic radiation that falls between microwaves and infrared light on the electromagnetic spectrum. They're valuable because they can manipulate materials at extremely high speeds. In the context of croconic acid, researchers used terahertz pulses to modulate its polarization on a sub-picosecond timescale. This rapid control is achieved by altering the distribution of π-electrons within the molecules of croconic acid, leading to changes in the material's polarization. This method offers a significant advantage for developing high-speed optical modulators.

How does manipulating the π-electrons in croconic acid with terahertz fields enable ultrafast polarization control?

By using terahertz pulses, researchers can rapidly alter the distribution of π-electrons within the molecules of croconic acid. The electric field from the terahertz pulse modifies the π-electron wavefunctions, directly influencing the material's polarization. The infrared molecular vibrational spectrum analysis confirms that the displacement of protons within the molecules plays a negligibly small role in the polarization changes. Therefore, the electronic nature of polarization is crucial in hydrogen-bonded molecular ferroelectrics like croconic acid, enabling the ultrafast control observed during the experiment.

What spectroscopic techniques were used to observe and understand the polarization modulation in croconic acid, and what did these techniques reveal?

The research team employed terahertz-pulse-pump second-harmonic-generation-probe (SHG) and optical-reflectivity-probe spectroscopy. The terahertz-pulse-pump SHG-probe measured changes in second harmonic generation to detect polarization modulation. Optical-reflectivity-probe spectroscopy observed changes in how light is reflected to understand alterations in π-electron wavefunctions. Additionally, infrared molecular vibrational spectrum analysis was used to determine the contribution of proton displacements to the polarization modulation. These techniques revealed that the amplitude of polarization modulation reached 10% through electric-field-induced modifications of π-electron wavefunctions and that proton displacements played a negligibly small role in the observed polarization changes.

What are the potential implications of using terahertz fields to control polarization in ferroelectrics like croconic acid for future technology?

The ability to achieve ultrafast polarization control via terahertz fields and π-electron systems in croconic acid signifies advancements in ferroelectrics. Since data transmission demands continue to grow, the use of terahertz-based control of ferroelectric polarization offers a solution to meet these challenges and unlock new possibilities in optical communications. The researchers suggest this approach can be extended to other hydrogen-bonded molecular ferroelectrics and can pave the way for future high-speed optical-modulation devices. This could lead to faster internet speeds, more efficient data centers, and advanced electronic and optical devices.

Croconic acid is identified as a key material; why is it so suitable for terahertz field manipulation compared to other ferroelectric materials?

Croconic acid is a hydrogen-bonded molecular ferroelectric with ferroelectricity. This means it can maintain an electric polarization that can be reversed by applying an external electric field. Croconic acid is particularly interesting because of the role of its π-electrons, which are theorized to contribute significantly to its ferroelectric properties. The polarization in croconic acid is primarily controlled by the π-electrons, which can be rapidly manipulated by terahertz fields. The electronic nature of polarization is what allows for the ultrafast control observed in the experiment.