A Northwestern University research team has found a way to manufacture single laser devices that are the size of a virus particle and that operate at room temperature. These plasmonic nanolasers could be readily integrated into silicon-based photonic（光激性的） devices, all-optical circuits and nanoscale biosensors. Reducing the size of photonic and electronic elements is critical for ultra-fast data processing and ultra-dense information storage. The miniaturization of a key, workhorse instrument -- the laser -- is no exception.

 

The results are published in the journal Nano Letters.

 

"Coherent light sources at the nanometer scale are important not only for exploring phenomena¹ in small dimensions but also for realizing optical devices with sizes that can beat the diffraction（衍射，绕射） limit of light," said Teri Odom, a nanotechnology expert who led the research.

 

Odom is the Board of Lady Managers of the Columbian Exposition Professor of Chemistry in the Weinberg College of Arts and Sciences and a professor of materials science and engineering in the McCormick School of Engineering and Applied² Science.

 

"The reason we can fabricate nano-lasers with sizes smaller than that allowed by diffraction is because we made the lasing cavity out of metal nanoparticle dimers -- structures with a 3-D 'bowtie' shape," Odom said.

 

These metal nanostructures support localized surface plasmons -- collective oscillations of electrons -- that have no fundamental size limits when it comes to confining light.

 

The use of the bowtie geometry has two significant benefits over previous work on plasmon lasers: (1) the bowtie structure provides a well-defined, electromagnetic hot spot in a nano-sized volume because of an antenna³ effect, and (2) the individual structure has only minimal⁴ metal "losses" because of its discrete⁵ geometry.

 

"Surprisingly, we also found that when arranged in an array, the 3-D bowtie resonators could emit light at specific angles according to the lattice parameters," Odom said.

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