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The tiny laser defies the diffraction limit of light. Scientists says these plasmonic nanolasers could be readily integrated into silicon-based photonic 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.

“Coherent light sources at the nanometer scale are important not only for exploring phenomena in small dimensions but also for realizing optical devices with sizes that can beat the diffraction limit of light,” says Teri Odom, professor of chemistry and of materials science and engineering at Northwestern University.

“The reason we can fabricate nanolasers with sizes smaller than that allowed by diffraction is because we made the lasing cavity out of metal nanoparticle dimmers—structures with a 3D ‘bowtie’ shape,” Odom says.

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

As reported in the journal Nano Letters, the use of the bowtie geometry has two significant benefits over previous work on plasmon lasers: the bowtie structure provides a well-defined, electromagnetic hot spot in a nano-sized volume because of an antenna effect; and the individual structure has only minimal metal losses because of its discrete geometry.

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

Source: Northwestern University