Kaunas University of Technology (KTU), Lithuania and scientists from Japan have developed a unique nanolaser. Despite its tiny dimensions, visible only through a powerful microscope, this nanolaser boasts vast potential. It holds promise for applications in early medical diagnostics, data communication, security technologies, and the study of light-matter interactions.
The Science Behind Nanolasers
Lasers vary in how they amplify and produce light, influencing the radiation’s colour and the laser beam’s quality. Nanolasers, in particular, operate on structures a million times smaller than a millimetre. These minuscule structures generate and amplify light in an extremely tiny volume of material.
“Nanolasers use structures a million times smaller than a millimetre to generate and amplify light. The laser radiation is created in an extremely tiny volume of material,” explains Dr Mindaugas Juodėnas, one of the researchers behind the invention.
A Unique Manufacturing Approach
While nanolasers have been explored previously, the version developed at KTU stands out due to its innovative manufacturing process. This method involves using silver nanocubes, which are precisely arranged on a surface and filled with an optically active material. The arrangement facilitates the amplification of light and the generation of the laser effect.
“Silver nanocubes are exceptionally small, monocrystalline particles with outstanding optical properties. They are an essential component of our nanolaser,” says Dr Juodėnas, a researcher at the KTU Institute of Materials Science.
These nanocubes are synthesised through a unique process developed by KTU’s Japanese partners, ensuring their precise shape and quality. Using a nanoparticle self-assembly process, the nanocubes naturally arrange themselves from a liquid medium into a pre-patterned template. When the template parameters align with the nanocubes’ optical properties, a phenomenon known as surface lattice resonance occurs, enabling efficient light generation.
The Hall of Mirrors Effect
Unlike conventional lasers that rely on mirrors, KTU’s nanolaser uses a nanoparticle-coated surface to produce laser radiation. “When silver nanocubes are arranged in a periodic pattern, light becomes trapped between them. It’s akin to a hall of mirrors in an amusement park, but here the mirrors are the nanocubes, and the visitor is light,” explains Dr Juodėnas.
This “trapped” light accumulates energy until it crosses the threshold for stimulated emission, producing an intense, directional beam of light with a specific colour. As Dr Juodėnas notes, the term “laser” itself stands for “light amplification by stimulated emission of radiation,” aptly describing this process.
Overcoming Challenges with International Support
KTU’s nanolaser requires minimal energy to operate, thanks to its use of high-quality, easily produced nanomaterials like silver nanocubes. This makes mass production feasible. “Chemically synthesised silver nanocubes can be produced in large volumes, and their high quality supports nanoparticle self-assembly technology. Even if the arrangement isn’t perfect, their properties compensate for it,” says Dr Juodėnas.
Initially, the simplicity of the method faced scepticism from Lithuanian research funding agencies. “Sceptics doubted whether such a simple method could create structures of sufficient quality for a working nanolaser,” recalls Professor Sigitas Tamulevičius.
However, the team’s unwavering belief in their invention secured funding from an international organisation, recognising the idea’s potential. “After extensive work and numerous experiments, we proved that even imperfect arrays could be effective when using high-quality nanoparticles,” notes Dr Juodėnas.
Future Applications
The nanolaser’s innovative design has already garnered international recognition, with related technologies receiving patents in the US and Japan. In the future, this nanolaser could be a crucial component in ultra-sensitive biological sensors for early disease detection or real-time monitoring of biological processes. Other potential applications include:
- Miniature photonic chips
- Identification and authentication devices
- Fundamental research into light-matter interactions on the nanoscale
The research paper, “Lasing in an assembled array of silver nanocubes,” is published in Nanoscale Horizons and is accessible here.
