Nanolattices

2022: ITMO studied direct laser recording of nanosets

On May 6, 2022, researchers at the Faculty of Nanoelectronics at ITMO University reported that, together with colleagues from FIAN, RKhTU named after D. I. Mendeleev and NIU MEPhI, they conducted a study in which they found out that nanosets have high spectral selectivity. Their layers can be used as filters for specific wavelengths, and up to six layers can be recorded on one glass plate. Thanks to this technology, scientists have implemented dispersion birefringent filters, which can be used for various applications: for example, to create biochemical sensors for diagnosing the flow of bacteria or augmented and virtual reality displays with a color image.

ITMO studied direct laser recording of nanosets

It was reported that for two years, scientists have been modeling, developing and testing integral optical elements to build a waveguide holographic periscope - a key element of augmented and virtual reality glasses of the next generation. Virtual reality helmets usually limit users' visibility - and smart glasses complement visual space and output additional information about objects and the environment.

To create such a device, you need to solve several problems, for example, how to transfer an image to a person through the glass of glasses and make the picture color. For this, researchers at ITMO laser-plasma method of glass processing (LIMP). It allows you to create laser beam converters that are actively used in the project to apply structures with a submicron period. The direct laser recording method then produced volumetric periodic structures within the glass with a modified refractive index. The next step will be to create submicron diffraction gratings on one glass plate to solve the problems of augmented and virtual reality. They are responsible for the input and output of the image to the observer through diffraction orders.

Our project is aimed at developing the basics of laser recording of integral elements in optical materials. As of May 2022, in the laboratory, a set of optical components (mirror, light source, filters, transducers and much more) occupies the entire optical table. We want to implement compact integrated optical circuits that are placed on the palm of the user, they are also called chip-scale devices. For example, we record light-conducting and selectively reflecting elements on a single glass matrix at several levels in 3D format. Such a circuit will be compact and protected from external influences. commented on Roman Zakoldaev, researcher at the Faculty of Nanoelectronics, one of the authors of the work

Work on the study was carried out by several teams. The first was engaged in direct laser recording in optical materials. The second team was responsible for measuring the morphology and physical properties of the micro- and nanostructures created. The third worked on theoretical modeling of physical and optical processes.

At the first stage, direct laser recording studies were carried out in various optical materials (quartz, multicomponent glasses, nanoporous glasses, calcium fluoride). These include samples that are used to develop glasses or are considered promising for creating holographic elements of augmented reality. Among such materials are nanoporous matrices, which are at ITMO University. Researchers use them in laser recording to optimize the efficiency of phase raid in a periodic volume structure with a submicron period.

Alexey Rupasov, a researcher at the Faculty of Nanoelectronics, investigates the morphology of nanosets with a period of 390 nm for subsequent modeling

Further, scientists experimented with different modes of direct laser recording in the volume of quartz glass: the duration of femtosecond laser pulses, fluence and wavelength of laser radiation were changed. As a result, it turned out that structure parameters, such as phase raid and light scattering, affect the spectral range of the obtained filters. In other words, the researchers managed to select laser recording modes, during which structures are formed with the largest value of phase raid and minimal scattering of light.

As a result, the researchers determined the dependence of phase raid on laser recording modes in quartz glass. Phase raid is a change in the refractive index in the thickness of quartz glass due to the formation of a periodic structure in a volume with different refractive indices (glass-air). From a physical point of view, these zones show a relatively large phase run (up to 166 degrees) in one layer, which is already almost a half-wave plate. In perspective, the obtained laser recording modes will allow to realize any phase optical element inside the glass. Due to the values ​ ​ of the phase run, the created structures are painted in birefringent colors if they are placed between polarizers.

Multilayer recording allows you to create dispersion birefringent filters in a given spectral range. This is already significant for the development of compact sensors that comply with the principles of integral optics with the function of spectral analysis. There are dispersion birefringent filters on the market, but these are separate optical elements. We decided to consider the integration of such filters on a single glass plate. Our work is fundamental, so we conducted simulations, and the results showed that it is possible to record multilayer structures for operation in the visible spectral range. explained Alexey Rupasov, one of the authors of the study, researcher at the Faculty of Nanoelectronics

This study result can be used as an element base for processing radiation in augmented reality devices in which an image is formed using three RGB color coordinates. Diffraction gratings will help realize the input and output of radiation in the waveguide for different wavelengths. In perspective, it is possible to create three kinds of periodic structures in one glass plate that adjust the radiation along the wavelengths of RGB and make the image colored.

Scientists also proposed the idea and design of an integral biochemical sensor for diagnosing the flow of bacteria. As of May 2022, there are already dispersion birefringent filters on the market for each wavelength separately, but now research can be carried out using one device in a "laboratory on a chip" - a glass substrate that is illuminated with polarized light. In it or outside there is a microfluidic chip where certain liquids flow with a detectable substance, for example, in the form of bacteria. Each such substance responds to a particular spectral range and wavelength of radiation, and it can also absorb light or fluoresce. With the help of the reaction, you can find out what changes in the chip are happening.

See also

• Nanoparticles in Medicine
• Nanofibers in medicine
• Boron nitride nano films

• Nanotubes
• Nanosprings