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Mid-Infrared Laser Technique May Help Detect Atmospheric Chemicals in Open Air

An innovative method of using mid-infrared lasers to turn regions of molecules in the open air into glowing filaments of electrically charged gas, or plasma, was found a couple of years ago. This new method could make it possible to carry out remote environmental monitoring to detect a wide range of chemicals with high sensitivity. The development of a new system is a merit of researchers at the Massachusetts Institute of Technology (MIT) in collaboration with researchers in Binghamton, New York (US), and Hamburg, Germany. This laser system makes use of a mid-infrared ultrafast pulsed laser to generate the filaments, whose colors can reveal the chemical fingerprints of different molecules.
The mid-IR wavelengths, rather than the near-IR, offer the greatest promise for detecting a wide variety of biomedical compounds and air pollutants. There are three elements that were used in the innovative scientific laser system:
A mid-infrared region of the light
The broadband mid-infrared wavelength laser pulses are highly sensitive molecular vibrations and rotations. So most of the chemicals have well-defined absorption lines in the wavelength range of 2-10 micrometer. These absorption lines are called molecular fingerprints.
Laser filamentation
One key to the success of this mid-infrared laser system is the use of a high-power femtosecond laser with pulses just 30 femtoseconds, or millions of a billionth of a second, long. The femtosecond laser with what is known as a parametric amplifier provided the necessary power for the quality work of the laser system. The aforementioned device produces one of the highest peak-power levels in the world at these mid-IR wavelengths. Such 30 femtosecond strong mid-IR laser pulses can generate laser filaments in open air. The laser filamentation enables the self-guided propagation of the beam over up to kilometers of distance thanks to balancing between nonlinear self-focusing and plasma defocusing. In the linear propagation without filamentation, the laser beam is diffracted and loses the confinement.
White light generation
White light generation is the spectral broadening, which is an important property of femtosecond filamentation.
One critical application of new mid-infrared laser system is the ability to detect industrial pollutants in the atmosphere and to remotely measure the density of carbon dioxide and ozone in the atmosphere. Monitoring the atmospheric chemicals is crucial for evaluating the global warming issue as well as protecting people’s health.
The mid-infrared laser system based on parametric amplifiers with ytterbium lasers is already regarded as an excellent platform of the next-generation femtosecond laser technique. Scientists around the world will be working with similar fiber laser architecture over the next 10 years and there will be many commercial products emerging with markets growing fast.
Optromix is a fiber laser vendor, which develops and manufactures a broad variety of fiber lasers, СО₂ lasers, Ti: Sapphire lasers, dye lasers, and excimer lasers. We offer simple erbium laser and ytterbium laser products, as well as sophisticated laser systems with unique characteristics, based on the client’s inquiry.
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