Making the Internet Move at the Speed of Light with New Optical Diodes
Edis Osmanbasic posted on June 25, 2019 |
(Image courtesy of Power Photonic.)
(Image courtesy of Power Photonic.)

Intense growth of internet traffic means that we’ll need even more advanced optical telecommunication systems that can process high-speed traffic. Using photons as data carriers,which are much faster than electrons, increases the speed and bandwidth of telecommunication systems. Unlike electrons,charged and controlled by external electric or magnetic fields, photons aren’t charged and are instead controlled by tuning media parameters. For this reason, researchers have been creating new materials, photonic crystals (PCs), with tunable parameters.

Optical diodes,or optical isolators,are widely used in computers and electronic devices for electrical signal processing. They enable light transmission in one direction,while blocking it in the opposite direction. The main task of such a device is to avoid unwanted optical reflections in optical systems.

Recently, researchers from Yerevan State University in Armenia and Far Eastern Federal University in Russia published a study in which they present the a model for new PCs made of materials with parameters easily tuned by external magnetic fields. The team analyzed the specifics of transmission and angular non-reciprocity in magneto-photonic crystals (MPCs) to find that a magnetic field interacts with a crystal inside an optical diode in such a way that the polarization of the light waves (which pass through the material) is rotated.

MPCs are created as a combination of plasmonic systems with magneto-optically active materials. The main idea is to control light propagation (transmission, reflection, refraction) by using an external magnetic field to modify plasmon properties. High values of magneto-optical activity can be obtained by exciting the plasmon. The researchers said, “MPCs are interesting because they provide mechanisms to miniaturize nonreciprocal components and to strongly enhance magneto-optical effects.”

Commercially available optical insulators based on linear polarizers and Faraday rotators are bulky and consume a lot of energy. Available optical diodes are based on solid PCs,in which the parameters aren’t controllable and usually have narrow bandwidths. Telecommunication systems require wide-bandwidth optical diodes.

Earlier MPCs haven’t been promising due to the fact a magnetic field can only provide minor modulations in light intensity and polarization.In this case, the researchers introduced ferroelectric and ferromagnetic nanoparticles with large gyrotropic parameters into the PCs to make them tunable, potentially a very promising method for enhancing the Faraday effect considerably.

Magneto-photonic crystal-magneto-optical spatial light modulator.(Image courtesy of the Journal of Nature Research.)
Magneto-photonic crystal-magneto-optical spatial light modulator.(Image courtesy of the Journal of Nature Research.)

In this case, the researchers have created photonic devices with adjustable properties, which will ensure a wide range of applications. The team’s wide/narrow-band MPC optical diode demonstrates high magneto-optical activity and modulation depth. The researchers have shown that changes in the direction of the external magnetic field are within the limits accepted for MPCs, without changing the nature of the of photonic band gap and its frequency location and width.

Improvements in optical isolator design are important form any applications, including any use in which stable laser diode operation is essential. They will also enahnce high-speed optical fiber transmittance amplifiers and routes, high speed photonic integrated circuits and switching applications, faster telecommunication systems and internet speeds.

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