Magnetically Controlled Nanolasers Protect Optical Signals

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A lasing control mechanism, introduced by a research team at Aalto University, enables users to control plasmonic nanolasers remotely, using a magnetic field. Until now, the only way to switch plasmonic nanolasers on and off has been through direct manipulation.

The ability to control nanolasers with magnets supports more robust optical signaling through the emerging field of topological photonics, which aims to produce light signals that are immune to external disruptions.

Where most plasmonic lasers are based on noble metals such as gold or silver, which render the optical mode structure of the laser inert to external fields, the Aalto researchers used a periodic array of cobalt-platinum multilayered nanodots, patterned on a continuous layer of gold and insulating silicon dioxide.

Using this design, the researchers exploited the magnetic nature of the nanoparticles to control the lasing action and demonstrated active magnetic-field control over lasing in the periodic array. Analysis showed that the material used to build the nanolaser and the arrangement of the nanodots in periodic arrays were critical to achieving magnetic control.

The research demonstrated that magnetization can be used to externally control plasmonic nanolasers in a manner that complements their modulation by excitation, gain medium, or substrate. Nanolasers can be more power-efficient than traditional lasers, and have been used to advantage in many fields, including biophotonics, where they have increased the sensitivity of biosensors used in medical diagnostics.

By enabling robust signal processing, the findings of the Aalto team could also influence the field of topological photonics. Up to now, strong magnetic fields have been required to create topologically protected optical signals using magnetic materials. The current work showed that the effect of magnetism in the context of on-and-off lasing can be unexpectedly amplified using a nanoparticle array of a particular symmetry.

The researchers believe that their work could lead to new, nanoscale, topologically protected signals.

“The idea is that you can create specific optical modes that are topological, that have certain characteristics which allow them to be transported and protected against any disturbance,” professor Sebastiaan van Dijken said. “That means if there are defects in the device or if the material is rough, the light can just pass them by without being disturbed, because it is topologically protected.

“Normally, magnetic materials can cause a very minor change in the absorption and polarization of light. In these experiments, we produced very significant changes in the optical response — up to 20%. This has never been seen before,” he said.

A plasmonic laser is turned on (top) and off (bottom) by switching the magnetization of a nanodot array. The zoomed insets show the magnetic field around a single nanodot. Courtesy of Jenna Rantala.
A plasmonic laser is turned on (top) and off (bottom) by switching the magnetization of a nanodot array. The zoomed insets show the magnetic field around a single nanodot. Courtesy of Jenna Rantala.
Professor Päivi Törmä, who collaborated with van Dijken on the research, said the results could lead to the realization of topological photonic structures in which magnetization effects can be amplified by choosing the appropriate nanoparticle array geometry.

The research was published in Nature Photonics (

Published: January 2022
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
topological photonics
Topological photonics is a branch of physics and optics that explores the application of topological concepts to the behavior of light in photonic systems. Drawing inspiration from the field of topological insulators in condensed matter physics, topological photonics investigates the manipulation and control of light waves in a way that is robust against certain imperfections or disorder. Key features and concepts in topological photonics include: Topological insulators: In condensed matter...
Plasmonics is a field of science and technology that focuses on the interaction between electromagnetic radiation and free electrons in a metal or semiconductor at the nanoscale. Specifically, plasmonics deals with the collective oscillations of these free electrons, known as surface plasmons, which can confine and manipulate light on the nanometer scale. Surface plasmons are formed when incident photons couple with the conduction electrons at the interface between a metal or semiconductor...
optical switching
Optical switching refers to the process of controlling the routing or transmission of optical signals within a network using various techniques to selectively switch or redirect optical paths. This is essential in optical communication systems, where data is transmitted as light signals over optical fibers. Optical switching technologies enable efficient, high-speed, and flexible routing of optical signals, enhancing the performance and scalability of optical networks. There are several types...
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