Scientists Develop First Liquid Nanolaser
Northwestern
University scientists have developed the first liquid nanoscale laser.
And it’s tunable in real time, meaning you can quickly and simply
produce different colors, a unique and useful feature. The laser
technology could lead to practical applications, such as a new form of a
“lab on a chip” for medical diagnostics.
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.
In addition to changing color in real time, the liquid nanolaser has
additional advantages over other nanolasers: it is simple to make,
inexpensive to produce and operates at room temperature.
Nanoscopic lasers -- first demonstrated in 2009 -- are only found in
research labs today. They are, however, of great interest for advances
in technology and for military applications.
“Our study allows us to think about new laser designs and what could be
possible if they could actually be made,” said Teri W. Odom, who led the
research. “My lab likes to go after new materials, new structures and
new ways of putting them together to achieve things not yet imagined. We
believe this work represents a conceptual and practical engineering
advance for on-demand, reversible control of light from nanoscopic
sources.”
Odom is Board of Lady Managers of the Columbian Exposition Professor of Chemistry in the Weinberg College of Arts and Sciences.
The findings were published by the journal Nature Communications.
The liquid nanolaser in this study is not a laser pointer but a laser
device on a chip, Odom explained. 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.
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. (In contrast to conventional laser cavities, no
mirrors are required for the light to bounce back and forth.) Notably,
as the laser color is tuned, the nanoparticle cavity stays fixed and
does not change; only the liquid gain around the nanoparticles changes.
The main advantages of very small lasers are:
• They can be used as on-chip light sources for optoelectronic integrated circuits;
• They can be used in optical data storage and lithography;
• They can operate reliably at one wavelength; and
• They should be able to operate much faster than conventional lasers because they are made from metals.
Some technical background
Plasmon lasers are promising nanoscale coherent sources of optical
fields because they support ultra-small sizes and show ultra-fast
dynamics. Although plasmon lasers have been demonstrated at different
spectral ranges, from the ultraviolet to near-infrared, a systematic
approach to manipulate the lasing emission wavelength in real time has
not been possible.
The main limitation is that only solid gain materials have been used in
previous work on plasmon nanolasers; hence, fixed wavelengths were shown
because solid materials cannot easily be modified. Odom’s research team
has found a way to integrate liquid gain materials with gold
nanoparticle arrays to achieve nanoscale plasmon lasing that can be
tuned dynamical, reversibly and in real time.
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.
These nanoscale lasers can be mass-produced with emission wavelengths
over the entire gain bandwidth of the dye. Thus, the same fixed
nanocavity structure (the same gold nanoparticle array) can exhibit
lasing wavelengths that can be tuned over 50 nanometers, from 860 to 910
nanometers, simply by changing the solvent the dye is dissolved in.
The National Science Foundation supported the research.
The title of the paper is “Real-time Tunable Lasing from Plasmonic Nanocavity Arrays.”
Source: Northwestern University