Laser in a vacuum produces transparent magnetic material

The laser heating setup for preparing a transparent magnetic material. Image: Taichi Goto et al.
The laser heating setup for preparing a transparent magnetic material. Image: Taichi Goto et al.

In a significant advance in optical technology, researchers from Tohoku University and Toyohashi University of Technology, both in Japan, have developed a new method for creating transparent magnetic materials using laser heating. This breakthrough, reported in a paper in Optical Materials, presents a novel approach to integrating magneto-optical materials with optical devices, a long-standing challenge in the field.

“The key to this achievement lies in creating ‘cerium-substituted yttrium iron garnet (Ce:YIG)’, a transparent magnetic material, employing a specialized laser heating technique,” says Taichi Goto, associate professor at Tohoku University’s Electrical Communication Research Institute (RIEC) and co-author of the paper. “This method addresses the key challenge of integrating magneto-optical materials with optical circuits without damaging them – a problem that has hindered advancements in miniaturizing optical communication devices.”

Magneto-optical isolators are vital for ensuring stable optical communication. They act like traffic directors for light signals, allowing them to move in one direction but not the other. Integrating these isolators into silicon-based photonic circuits has proved challenging, however, due to the high-temperature processes typically involved.

As a result of this conundrum, Goto and his colleagues focused their attention on laser annealing – a technique that selectively heats specific areas of a material with a laser. This allows for precise control, influencing only the targeted regions without affecting surrounding areas.

Previous studies have used laser annealing to selectively heat films of a related material – bismuth-substituted yttrium iron garnet (Bi: YIG) – deposited on a dielectric mirror. This allows the Bi:YIG to crystalize without affecting the dielectric mirror.

However, when working with Ce:YIG, an ideal material for optical devices due to its magnetic and optical properties, problems arise because exposure to the air results in unwanted chemical reactions.

To avoid this, the researchers engineered a new device that can heat materials in a vacuum, i.e. without air, using a laser. This allowed for precise heating of small areas (about 60µm) without altering the surrounding material.

“The transparent magnetic material created through this method is expected to significantly enhance the development of compact magneto-optical isolators, crucial for stable optical communication,” says Goto. “Additionally, it opens avenues for creating powerful miniaturized lasers, high-resolution displays and small optical devices.”

This story is adapted from material from Tohoku University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.

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