The ever-evolving field of optoelectronics, encompassing devices that detect, control, or emit light, is integral to numerous everyday technologies.

These include light-emitting diodes (LEDs), optical fibres, and medical imaging devices. As the demand for more efficient and advanced optoelectronic devices increases, researchers continuously seek novel materials and techniques to enhance the functionality of these devices. A recent discovery at the Department of Energy's SLAC National Accelerator Laboratory has unveiled promising new behaviour in an ultrathin material, offering a fresh approach to manipulating light.

While conducting experiments with a high-speed electron camera, researchers at SLAC uncovered intriguing properties in an ultrathin film of tungsten ditelluride. This material, when aligned in a specific direction and exposed to linear terahertz radiation, circularly polarizes the incoming light. This discovery, led by SLAC and Stanford professor Aaron Lindenberg and reported in Nano Letters, highlights the potential of tungsten ditelluride in enhancing the performance of optical devices by effectively polarizing light.

Terahertz radiation, situated between the microwave and infrared regions of the electromagnetic spectrum, presents unique opportunities for characterising and controlling material properties. Scientists aim to leverage this form of light for the advancement of optoelectronic devices. To observe the behaviour of materials under terahertz radiation, advanced instruments capable of capturing ultrafast interactions are essential. The Linac Coherent Light Source (LCLS) at SLAC houses such a device, the MeV-UED (ultrafast electron diffraction instrument), which is pivotal in this research.

Traditionally, the MeV-UED is used to visualise atomic motion by measuring electron scattering after an electron beam impacts a sample. However, in this study, the researchers utilised femtosecond electron pulses to visualise the electric and magnetic fields of the terahertz pulses. These pulses induced a wiggling motion in the electrons, forming a circular pattern that indicated circular polarisation.

The tungsten ditelluride film used in the experiment was extraordinarily thin, measuring just 50 nanometres. "This is 1,000 to 10,000 times thinner than what we typically need to induce this type of response," Lindenberg noted. This significant reduction in material thickness opens up exciting possibilities for creating smaller, more efficient optoelectronic devices.

The potential applications of these ultrathin, two-dimensional (2D) materials are vast. Researchers envision constructing devices from layered 2D structures, akin to stacking Lego bricks. Each layer, composed of a different material, would be precisely aligned to produce a specific optical response. This method allows for the combination of diverse structures and functionalities into compact devices, which could revolutionise fields such as medical imaging and other optoelectronic technologies.

"This work represents another element in our toolbox for manipulating terahertz light fields, which in turn could allow for new ways to control materials and devices in interesting ways," said Lindenberg. His statement underscores the broad potential of this research in developing innovative methods to control light and enhance the capabilities of various devices.

The findings at SLAC highlight a significant advancement in the field of optoelectronics. By exploring the properties of ultrathin materials like tungsten ditelluride under terahertz radiation, scientists are paving the way for the next generation of optoelectronic devices. This research not only provides a deeper understanding of light polarisation within materials but also opens up new avenues for developing smaller, more efficient devices with enhanced functionalities. The continued exploration and manipulation of 2D materials promise to drive further innovations, ultimately benefiting a wide range of technologies that are integral to our daily lives.

Author:

Alex Carter

Content Producer and Writer

Nano Magazine 

Image