A group of scientists from Northwestern University and Duke University has found a way to manufacture a liquid nanoscopic laser whose emission properties can be modulated in real time.
This image shows a nano-lasing device consisting of gold nanoparticle arrays and a microfluidic channel fabricated by sandwiching a 250 μm-thick silicone sheet with a 5-mm-wide and 15-mm-long slit in the center between the gold nanoparticle substrate and a glass microscope slide. Image credit: Ankun Yang et al.
“The liquid nano-laser is not a laser pointer but a laser device on a chip,” said Prof Teri Odom of Northwestern University, who is the senior author on the study published in the journal Nature Communications.
To understand the concept, imagine a laser pointer whose color can be changed simply by changing the liquid inside it, instead of needing a different laser pointer for every desired color.
“The laser’s color can be changed in real time when the liquid dye in the microfluidic channel above the laser’s cavity is changed,” Prof Odom said.
The use of liquid gain materials has two significant benefits.
“The organic dye molecules can be readily dissolved in solvents with different refractive indices. Thus, the dielectric environment around the nanoparticle arrays can be tuned, which also tunes the lasing wavelength.”
“The liquid form of gain materials enables the fluid to be manipulated within a microfluidic channel. Thus, dynamic tuning of the lasing emission is possible simply by flowing liquid with different refractive indices. Moreover, as an added benefit of the liquid environment, the lasing-on-chip devices can show long-term stability because the gain molecules can be constantly refreshed.”
In addition to changing color in real time, the laser developed by Prof Odom’s team has additional advantages over other nano-lasers: it is simple to make, inexpensive to produce and operates at room temperature.
The laser’s cavity is made up of an array of reflective gold nanoparticles, where the light is concentrated around each nanoparticle and then amplified.
Notably, as the laser color is tuned, the nanoparticle cavity stays fixed and does not change; only the liquid gain around the nanoparticles changes.
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Ankun Yang et al. 2015. Real-time tunable lasing from plasmonic nanocavity arrays. Nature Communications 6, article number: 6939; doi: 10.1038/ncomms7939
