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Pulses of light to encrypt and protect

Credit Vinh Diep and Alexa Hudnut

Researchers at the USC Viterbi School of Engineering have developed a frequency comb, in a hope to create an effective tool for data encryption.

According to experts, the current system, in which data travels through fibre optic cables, is at risk of being intercepted.

The comb has been designed to increase the potential applications of lasers by converting a single wavelength into multiple wavelengths, effectively creating tens to hundreds of lasers from a single laser.

The current state of the art relies on material systems traditionally used in microelectronics. The material in this device was replaced with carbon-based or organic molecules. Attaching only a single layer of a 25-atom organic molecule to the surface of a laser, the researchers said the frequency combs were demonstrated with 1000x reduction in power.

Professor Armani from the USC Viterbi School of Engineering, said: "Organic optical materials have already transformed the electronics industry, leading to lighter, lower power TVs and cellphone displays, but previous attempts to directly interface these materials with lasers stumbled.

"We solved the interface challenge. Because our approach can be applied to a wide range of organic materials and laser types, the future possibilities are very exciting."

The frequency comb also has prospects within quantum cryptography.

A current limitation of encryption is that when it has failed, it’s not possible to detect. With quantum encryption, complex keys be implemented and intrusions are said to be immediately apparent through changes in the transmitted data signal.

One strategy that is being investigated is photon entanglement. Entangled pairs of photons must be created at exactly the same time, with exactly the same properties.

The first step in forming the frequency comb occurs when the primary laser generates a secondary pair of wavelengths. However, because of energy conservation, one wavelength must have higher energy and one wavelength must have lower energy. Additionally, the energies must sum to be exactly equal to the primary laser, and the two new wavelengths must appear at exactly the same time. Thus, frequency comb generators can be viewed as entangled photon generators.

Prof Armani also indicated that that in addition to the important role that quantum encryption could play in securing our healthcare information in the future, frequency combs are also being used to improve the detection of cancer biomarkers.

Bethan Grylls

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