Model Guides Precise Formation of Plasmonic Components

Using a real-time mathematical analysis model developed at ITMO University, scientists will now be able to manipulate the process of creating photonic and plasmonic components to produce the precise optical properties that are needed in a material. Based on the method developed by the ITMO scientists, they will be able to predict with high accuracy the optical properties of a plasmonic component during the treatment process.

Composite materials, such as glass enhanced with metal nanoparticles, show high potential for use in optical devices. Depending on which metal ions are added into glass, the resulting composite can be used to manipulate various parts of the spectrum. “Such materials can be used as optical filters,” researcher Pavel Varlamov said. “White light, as we know, consists of a large number of wavelengths and you might need to, for example, highlight or exclude a certain spectrum band. That’s what optical filters are for, and they can be used in lasers or refractors.”

(l) to (r): ITMO researchers Maksim M. Sergeev, Roman A. Zakoldaev, and Pavel V. Varlamov. Courtesy of ITMO.news.

The ITMO team conducted a stage-by-stage study of the changes in structure that occurred within composite materials. The team registered the changes in the sample’s transmission capacity depending on the duration of laser irradiation. It then performed an analysis of the optical constants of nanoparticles during the irradiation, and modeled the spectral properties of the resulting elements.

Spectral microanalysis of the irradiated region showed a multilayer plasmonic structure inside the glass composite. The researchers were able to connect the measured spectral data to the numerically estimated size, concentration, and chemical composition of the secondary phase across the initial sample and the fabricated structure.

Adding nanoparticles into regular glass is a complex process involving numerous chemical reactions. That’s why scientists prefer to use nanoporous glass for this purpose. Once nanoparticles have been fitted into the pores of the glass, the material is irradiated with a laser to give it new optical properties that will make it possible for the composite material to accurately control the light spectrum by transmitting or absorbing light beams of a specific band.

However, during the treatment process, the material changes the way it interacts with the laser radiation and begins to better absorb radiation within a specific band of the spectrum. The laser must be tuned to continuously adjust to the changes that occur within the material. To tune the laser’s performance throughout treatment, scientists need to calculate the changes that have already occurred during treatment and any changes that need to be made to the laser’s settings. For these calculations, they need a flexible algorithm.

The ITMO team designed a mathematical model that took into account the strength of the radiation and the changes it would cause in the material. This made it possible to monitor the optical properties of the material while it was subject to laser treatment.

“We were able to propose a calculation algorithm that presents the electronic structure, size, and concentration of nanoparticles with the optical properties of [the] material as one effective environment,” researcher Maksim Sergeev said. “Using the algorithm together with a model of diffusion-controlled growth of particles has made it possible for us to trace the optical changes in laser treatment in real time.” The researchers further proposed a contactless method of identifying the volume, concentration, and chemical composition of nanoparticles in any given part of a produced object.

“The method we’ve suggested makes it possible to create voluminous microscale elements with a plasmonic resonance peak that can be controlled in real time,” researcher Roman Zakoldaev said. “The method aims to optimize the parameters of laser altering via feedback.”

The method proposed by the ITMO team could make the creation of optical plasmonic components cheap and easy to handle, opening up new opportunities for integrating these components into industrial production.

The research was published in Nanomaterials (www.doi.org/10.3390/nano10061131).