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Scientists at Northwestern University have created the first-ever liquid nanoscale laser that can be tuned in real time to generate multiple colors easily and rapidly. This unique and convenient feature of this laser technology could pave the way for several practical applications including a new “lab on a chip” for medical purposes.
To explain this concept, consider a laser pointer, the color of which can be altered by changing the liquid present in it, instead of requiring different pointers for preferred colors.
The other benefits of the liquid nanolaser over conventional nanolasers include cost-effectiveness, easy manufacturing process and operation at room temperature.
The nanoscopic lasers were first introduced in 2009, and they are now available only at research labs. However, these lasers are in great demand for military applications and other technological advancements.
Our study allows us to think about new laser designs and what could be possible if they could actually be made. 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.
Teri W. Odom, Board of Lady Managers of the Columbian Exposition Professor of Chemistry in the Weinberg College of Arts and Sciences
Odom explained that the liquid nanolaser is not a laser pointer but actually a laser device on a chip. The change of laser color is real time is accomplished by changing the liquid dye present in the microfluidic channel on top of the laser’s cavity.
The laser’s cavity constitutes a reflective gold nanoparticle array where each nanoparticle is illuminated with the light and amplified. Unlike conventional laser cavities, these cavities do not require mirrors for back and forth light radiation. While tuning the laser color, the nanoparticle cavity remains constant without any change. It is only the liquid gain that changes around the nanoparticle.
The small lasers have a number of advantages as follows:
- Metallic design enables faster operation than conventional lasers
- Reliable operation at single wavelength
- Applications in optical data storage and lithography
- Serves as on-chip light sources for optoelectronic integrated circuits
Plasmon lasers hold great promise in nanoscale coherent sources used in optical applications owing to their ultra-fast dynamics and ability to support ultra-small sizes. These lasers have been used at spectral ranges varying from ultraviolet to near-infrared. However, a systematic method for a real-time manipulation of the lasing emission wavelength has not been identified.
One of the main limitations in previous work carried out on plasmon nanolasers is the use of only solid gain materials. As a result, fixed wavelengths were displayed as modification of solid materials is not easily possible. Odom’s research team has however identified a new method of achieving nanoscale plasmon lasing by incorporating liquid gain materials into gold nanoparticle arrays. This laser can be reversibly and dynamically tuned in real time.
The following are the two major benefits of using liquid gain materials:
- The liquid gain materials facilitate manipulation of the fluid in a microfluidic channel thereby enabling dynamic tuning of the lasing emission using liquid with different refractive indices. In addition, the lasing-on-chip devices exhibit long-term stability due to continuous refreshment of the gain molecules.
- The dissolution of organic dye molecules in solvents having varying refractive indices allows tuning of the dielectric environment around the nanoparticle arrays, which in turn tunes the wavelength of laser.
Using emission wavelengths over the gain bandwidth of the dye, mass-production of these nanoscale lasers can be performed. The lasing wavelengths of the same fixed nanocavity structure can be tuned in the range of 860 to 910nm by changing the solvent in which the dye is dissolved.
The research published in the journal Nature Communications was supported by the National Science Foundation.
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