Novel Laser Technology for Microchip-Size Chemical Sensors


The laser releases light with really unique spectral homes.

Many lasers have just one color. All the photons it releases have precisely the exact same wavelength. Nevertheless, there are likewise lasers whose light is more complex. If it includes several frequencies, with equivalent periods in between, much like the teeth of a comb, it is described as a“frequency comb” Frequency combs are ideal for discovering a range of chemical compounds.

Das Forschungsteam vom Institut für Festkörperelektronik: Benedikt Schwarz, Aaron Maxwell Andrews, Gottfried Strasser, Johannes Hillbrand, Hermann Detz (v.l.n.r) Benedikt Schwarz, Aaron Maxwell Andrews, Gottfried Strasser, Johannes Hillbrand, Hermann Detz (delegated right)

At TU Wien (Vienna), this unique kind of laser light is now utilized to allow chemical analysis on small areas– it is a millimeter-format chemistry laboratory. With this brand-new patent-pending technology, frequency combs can be produced on a single chip in an extremely easy and robust way. This work has actually now existed in the journal “Nature Photonics”.

A comb with a Nobel Reward
Frequency combs have actually been around for years. In 2005, the Nobel Reward for Physics was granted for this. “The exciting thing about them is that it is relatively easy to build a spectrometer with two frequency combs,” describes Benedikt Schwarz, who heads the research study task. “It is possible to make use of beats between different frequencies, similar to those that occur in acoustics, if you listen to two different tones with similar frequency. We use this new method, because it does not require any moving parts and allows us to develop a miniature chemistry lab on a millimetre scale.”

At the Vienna University of Technology, frequency combs are produced with quantum waterfall lasers. These unique lasers are semiconductor structures that include several layers. When electrical existing is sent out through the structure, the laser releases light in the infrared variety. The homes of the light can be managed by tuning the geometry of the layer structure.

“With the help of an electrical signal of a specific frequency, we can control our quantum cascade lasers and make them emit a series of light frequencies, which are all coupled together,” states Johannes Hillbrand, very first author of the publication. The phenomenon is similar to swings on a rocking frame– rather of pressing specific swings, one can make the scaffolding wobble at the best frequency, triggering all the swings to oscillate in specific paired patterns. “The big advantage of our technology is the robustness of the frequency comb,” states Benedikt Schwarz. Without this method, the lasers are incredibly conscious disruptions, which are inevitable outside the laboratory– such as temperature level changes, or reflections that send out a few of the light back into the laser. “Our technology can be realized with very little effort and is therefore perfect for practical applications even in difficult environments. Basically, the components we need can be found in every mobile phone”, states Schwarz.

The molecular finger print
The reality that the quantum waterfall laser creates a frequency comb in the infrared variety is important, since a lot of the most crucial particles can best be spotted by light in this frequency variety. “Various air pollutants, but also biomolecules, which play an important role in medical diagnostics, absorb very specific infrared light frequencies. This is often referred to as the optical fingerprint of the molecule, “explains Johannes Hillbrand. “So, when we measure, which infrared frequencies are absorbed by a gas sample, we can tell exactly which substances it contains.”

Measurements in the microchip
“Because of its robustness, our system has a decisive advantage over all other frequency comb technologies: it can be easily miniaturized,” states Benedikt Schwarz. “We do not need lens systems, no moving parts and no optical isolators, the necessary structures are tiny. The entire measuring system can be accommodated on a chip in millimeter format.”

This leads to incredible application concepts: one might put the chip on a drone and step air contaminants. Chips glued to the wall might browse for traces of explosive compounds in structures. The chips might be utilized in medical devices to identify illness by evaluating chemicals in the breathing air.

The brand-new technology has actually currently been patented. “Other research study groups are currently extremely thinking about our system. We hope that it will quickly be utilized not just in scholastic research study, however likewise in daily applications, “states Benedikt Schwarz.

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