Modern optical devices need to constantly change their characteristics of interacting with light. For this are various mechanical devices that move the lens, turn the reflecting surface, move the laser emitters. An international group of scientists, which included staff of the ITMO University and Exeter University, proposed a new metamaterial that can change its optical characteristics without any mechanical impact. This can significantly increase the reliability and reduce the cost of production of complex optical devices.
The rapid development of science in recent decades has given mankind a very wide range of new materials. Now the creators of the complex mechanisms less need to adapt to the limitations imposed by their imagination traditional materials. Great prospects open in this sense, the so-called metamaterials, to create a work specifically in the University ITMO. Due to the complex structure of the constituent elements and the functionality of such structures to a lesser extent, is limited by the properties of the materials from which they are made. Metamaterials can be large, and may be flat – in this case, they are called setpowermode.
“Setpowermode can achieve many interesting effects in the management of the light, – says senior researcher at the New Institute of the University ITMO Ivan Sinev. – However, they have a problem – all of their properties are laid at the time of production and continue to remain unchanged. For devices of practical application I would like these properties to control not only the moment of creation, but as you use”.
In search of material for this adaptive optics, researchers from the ITMO University, with extensive experience in working with silicon setpowermode, teamed up with colleagues from the English University of Exeter who have long been studying the materials with the phase memory. Such substances include, for example, compounds of germanium, antimony and tellurium (GeSbTe), which are often used in DVDs.
“We’ve done calculations of how should look the new composite material based on silicon, – says the engineer of the New physics Paul Trofimov – the insertion of GeSbTe we have presented in the form of a thin layer between two layers of silicon. Turns out this sandwich – first, on the source substrate silicon is deposited, then a layer of the material with phase memory, then re-silicon”.
Then, using electron beam lithography, scientists have obtained a microscopic arrays of hybrid CDs – metaphorist, which already worked in the lab, checking its properties for light control. As expected, the combination of the two materials gave PTS��n important effect – the level of transparency of the resulting surface can be varied during the experiment. The fact that the silicon disc is in the near infrared range two optical resonance, which allow particularly hard to reflect is directed towards the surface of the IR beam. The GeSbTe layer is allowed under certain conditions to “switch off” one of these resonances, making the disc is almost completely transparent to light in the near infrared spectrum. The results of the researchers ‘ work appeared on the cover of the journal Optica.
Materials with functional memory have two States – crystalline, with a rigid ordered structure of atoms, and amorphous. If located in the center of the metamaterial layer GeSbTe will remain in the crystalline state, the second resonance disappears, if amorphous, the disk will still reflect the IR rays.
“to switch netpowersoft between two States we used a pulsed laser with sufficiently high energy, – says Trofimov, a short laser pulse heats the GeSbTe layer to the melting point, after which he cools down quickly and amortized. If the drive to work with a series of short pulses, it cools more slowly, freezing in the crystal structure”.
The properties of the new setpowermode can be useful for a variety of applications. First of all, the creation of a lidar device scanning the space by radiation and reception of reflected objects of the IR pulses. Also potentially the principle of their creation can be used as a basis for the production of special ultra-fine lens for camera lenses, for example, installed in mobile phones.
