Liquid crystals could help hijack laser pointer attacks on aircraft

Directing a laser beam on an aircraft is not a harmless joke: the sudden flash of bright light can render the pilot unsuitable, thus endangering the lives of passengers and crew. But since attacks can occur with different colors of lasers, such as red, green or even blue, scientists have struggled to develop a unique method to block all wavelengths of laser light . The researchers today report the presence of liquid crystals that can be incorporated one day into the windshield of an aircraft in order to block any intense and concentrated light color.

The researchers will present their findings today at the 2019 Spring National Meeting and Exposition of the American Chemical Society (ACS).

According to the Federal Aviation Administration, 6,754 laser strikes on aircraft were reported in 2017. "Staff at our university's aviation department told us about the growing problem at airports around the world. and landing, the critical phases of the flight, "says Jason Keleher, Ph.D., principal investigator of the project. Such attacks, which cause flashes of light in the cockpit, may distract pilots or cause temporary or permanent visual damage, depending on the wavelength and intensity of the laser.

"We wanted to come up with a solution that does not require us to completely rethink the windshield of an airplane, but rather add a layer to the glass that leverages the existing power system for windshield defrosting" says Daniel Maurer, undergraduate student. . Keleher and Maurer are at Lewis University.

Rather than being integrated into the windshield, previous approaches included windshields or goggles that pilots put on during take-off and landing. These can be troublesome, however, as they require the flight crew to take these precautions, whether or not they are targeted. An even more important problem is that these strategies only work for specific wavelengths of the laser light. "They do not block everything," says Maurer. "They are usually focused on green lasers because they are used for the majority of attacks."

To develop their new approach, researchers have taken advantage of liquid crystals, materials with properties comparable to those of liquids and solid crystals, which make them useful for electronic displays. The team placed a liquid crystal solution called NOT– (4-Methoxybenzylidene) -4-butylaniline (MBBA) between two 1-inch square glass panes. MBBA has a transparent liquid phase and an opaque crystalline phase that diffuses light. By applying a voltage to the device, the researchers made sure that the crystals aligned with the electric field and undergo a phase change to the crystalline state more solid.

The aligned crystals blocked up to 95% of the red, blue and green beams through a combination of light scattering, laser energy absorption and cross polarization. Liquid crystals could block lasers of different powers simulating different illumination distances, as well as light projecting the glass from different angles.

In addition, the system was fully automatic: a photoresistor detected the laser light and then activated the power system to apply the voltage. When the beam was removed, the system turned off the power and the liquid crystal returned to its liquid and transparent state. "We only want to block where the laser hits the windshield and get it back to normal once the laser is gone," says Keleher. The rest of the windshield, which has not been touched by the laser, will remain transparent at all times.

Now that researchers have proven that their approach is working well, they are planning to move from the size of an inch to the size of a full airplane windshield. Early results showed that a sensor grid pattern on 2-inch glass squares would only respond to the illuminated glass section. The team is also testing different types of liquid crystals to find even more effective and versatile crystals that return to the transparent state faster once the laser is removed.

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More information:
Molecular structure analysis of liquid crystals to develop wavelength-independent films to mitigate laser attacks on aircraft, National Spring-2019 Exposition of the American Chemical Society (ACS) )