New mid-infrared Laser System could detect Atmospheric Chemicals


An increasing number of different laser technologies can be used to access the mid-infrared spectral region. Researchers at Massachusetts Institute of Technology (MIT) have invented a new technique of using mid-infrared lasers. In this new technique, mid-infrared lasers are used to change the area of molecules in the open air into glowing strand of electrically charged gas, or plasma. This new technique can enable different environmental controlling to identify a wide range of chemicals with high sensitivity.

The new system uses a mid-infrared ultra-fast pulsed laser system to produce the strains. Its colors can unveil the chemical fingerprints of different molecules.

Kyung-Han Hong, investigator of MIT’s Research Laboratory of Electronics explained, these strains are produced by lasers in the near-infrared part of the electromagnetic spectrum. A study has been already done it because of their hopeful uses like laser-based range finding and remote sensing. The phenomenon of this strain is produced by high-power lasers. It supplies to opposite emission effects that usually take place when a laser beam passes through the air. When the power level reaches a specific point and once the strains are produced, due to reaching the power level at a specific point, they give a type of self-guiding channel that keeps the laser beam tightly focused.

It is the mid-infrared (mid-IR) wavelengths, which offers lots of variety of biochemical compounds and air pollutants. Although, researchers who tried to produce mid-IR strains in open air had little success until now.

Hong said, “A previous research team was the only one who has successes in creating mid-IR laser strains in air. But it had a too slower rate of about 20 pulses per second. The new work uses 1,000 pulses per second is the first to be carried out at the high rates needed for practical detection tools.”

Hong said, “People want to use this kind of technology to detect chemicals in the far distance, several kilometers away. For that, we had very hard time to make such systems enable. We used a high power femtosecond laser with pulses just 30 femtoseconds, or millionths of a billionth of a second, long. The longer the wavelength, the more laser peak power is needed to produce the expended strains, due to stronger emission.”

“The team’s femtosecond laser was connected with a parametric amplifier for providing essential power for the task,” he then said.

Along with Franz X. Kaertner in Hamburg and other group members, this new laser system has been developed simultaneously. At the mid IR wavelengths, this device can generate 100 gigawatts (GW, or billion watts) of peak power. This is one of the highest peak power levels in the world.

It takes minimum 45 GW of power to produce the strains at these mid-infrared wavelengths. Thus, this device easily meets that requirement and proved that it did indeed work as expected. Now it increases the potential for checking a very wide range of compounds in the air, from a distance.

Hong said, “By using spectrally extended mid-IR laser strains, we can identify virtually any kind of molecule you want to detect broadened mid-IR laser filaments. We can detect virtually any kind of molecule you want to detect. For example, different biohazards and pollutants, by detecting the exact color of the filament. In the mid-IR range, the absorption spectrum of specific chemicals can be easily analyzed.”

“Although, the experiments have been limited to shorter distances inside the lab. But the team expecting, there is no reason the same system would not work, with further development, at much larger scales. This is just a proof-of-principle demonstration,” Hong says.

Pavel Polynkin, an associate research professor of optical sciences at the University of Arizona, said that “This technique is the first innovation of self-channelling of ultra-intense mid-IR laser pulses in the air. This will have new and exciting applications, time will show.”

“I think there is an agreement in the ultra fast laser community that the investigation of the mid-infrared spectral domain is going to be a new perimeter in ultra fast laser science. The extension of intense atmospheric propagation manages into the mid-IR spectral range. It certainly holds a lot of promise to overcome the limitations associated with the very well-explored near-IR spectral range, namely the very unstable propagation dynamics in the near-IR. The authors tapped into a new domain of intense nonlinear optics. Without a doubt there will be follow-up work”, he then said.