Mirbek Turduev

Bio: Mirbek Turduev is an academic researcher from Ankara University. The author has contributed to research in topics: Photonic crystal & Photonics. The author has an hindex of 16, co-authored 88 publications receiving 711 citations. Previous affiliations of Mirbek Turduev include TOBB University of Economics and Technology.

Experimental studies on chemical concentration map building by a multi-robot system using bio-inspired algorithms

Abstract: In this article we describe implementations of various bio-inspired algorithms for obtaining the chemical gas concentration map of an environment filled with a contaminant. The experiments are performed using Khepera III and miniQ miniature mobile robots equipped with chemical gas sensors in an environment with ethanol gas. We implement and investigate the performance of decentralized and asynchronous particle swarm optimization (DAPSO), bacterial foraging optimization (BFO), and ant colony optimization (ACO) algorithms. Moreover, we implement sweeping (sequential search algorithm) as a base case for comparison with the implemented algorithms. During the experiments at each step the robots send their sensor readings and position data to a remote computer where the data is combined, filtered, and interpolated to form the chemical concentration map of the environment. The robots also exchange this information among each other and cooperate in the DAPSO and ACO algorithms. The performance of the implemented algorithms is compared in terms of the quality of the maps obtained and success of locating the target gas sources.

Mid-infrared T-shaped photonic crystal waveguide for optical refractive index sensing

Abstract: In this paper, we propose and design a new type of an integrated optical sensor that performs sensing in a wide wavelength range corresponding to mid-infrared (mid-IR) spectrum. By engineering the structural parameters of square-lattice photonic crystal (PC) slab incorporated with a T-shaped air-slot, strong light confinement and interaction with the analytes are assured. Numerical analyses in the time and frequency domain are conducted to determine the structural parameters of the design. The direct interaction between the slot waveguide mode and the analyte infiltrated into the slot gives rise to highly sensitive refractive index sensors. The highest sensitivity of the proposed T-slotted PC sensor is 1040 nm/RIU within the range of analytes’ refractive indices n = 1.05-1.10, and the overall sensitivity corresponding to the higher refractive index range of n = 1.10-1.30 is around 500 nm/RIU. Moreover, for a realistic PC slab structure, we determined an average refractive index sensitivity of 530 nm/RIU within the range of n = 1.10-1.25 and an average sensitivity of 390 nm/RIU within the range of n = 1.00-1.30. Furthermore, we speculate on the possible approach for the fabrication and the optical characterization of the device. The assets of the device include being compact, having a feasible measurement and fabrication technique, and possessing label-free sensing characteristic. We expect that the presented work may lead to the further development of the mid-IR label-free biochemical sensor devices for detection of various materials and gases in the near future.

Ultracompact Photonic Structure Design for Strong Light Confinement and Coupling Into Nanowaveguide

Abstract: Different optimization algorithms have recently been utilized to design and improve the performance of many nanophotonic structures. We present the design of a compact photonic structure by an approach based on machine learning. Three-dimensional finite-difference time-domain method is integrated with a machine learning algorithm in order to design a photonic structure. In particular, a subwavelength focusing lens structure that operates at telecom wavelengths is designed to have desired beam properties such as subwavelength full-width at half-maximum value of 0.155 λ and suppressed side-lobe levels at focal point, where λ denotes the wavelength of incident light and equals to 1550 nm. The designed compact lens structure has the footprint of ${\text{2}}\times {\text{1}}\,{\mu} {\text{m}}^{\text{2}}$ with a slab thickness of 280 nm, which is the smallest photonic lens for subwavelength focusing of light to date comparing to its conventional ones. The focusing mechanism of designed lens structure is explained with the help of applying discrete Fourier transform to the two-dimensional dielectric distribution of the structure. It is also shown that, due to its strong light confinement property, the designed lens structure can be used as a waveguide-to-waveguide optical coupling device with a beamwidth compression ratio of 10:1 by integrating a nanowaveguide with the width of 200 nm to the output surface of lens structure. Normalized transmission efficiency of the optical coupling device is calculated as high as 0.62 at the wavelength of 1550 nm. The outcomes of the presented study show that machine learning can be beneficial for designing efficient compact photonic structures.

Two-dimensional complex parity-time-symmetric photonic structures

Abstract: We propose a simple realistic two-dimensional complex parity-time-symmetric photonic structure that is described by a non-Hermitian potential but possesses real-valued eigenvalues. The concept is developed from basic physical considerations to provide asymmetric coupling between harmonic wave components of the electromagnetic field. The structure results in a nonreciprocal chirality and asymmetric transmission between in- and out-coupling channels into the structure. The analytical results are supported by a numerical study of the Bloch-like mode formations and calculations of a realistic planar semiconductor structure.

Differential evolution algorithm based photonic structure design: numerical and experimental verification of subwavelength λ/5 focusing of light.

Abstract: Photonic structure designs based on optimization algorithms provide superior properties compared to those using intuition-based approaches. In the present study, we numerically and experimentally demonstrate subwavelength focusing of light using wavelength scale absorption-free dielectric scattering objects embedded in an air background. An optimization algorithm based on differential evolution integrated into the finite-difference time-domain method was applied to determine the locations of each circular dielectric object with a constant radius and refractive index. The multiobjective cost function defined inside the algorithm ensures strong focusing of light with low intensity side lobes. The temporal and spectral responses of the designed compact photonic structure provided a beam spot size in air with a full width at half maximum value of 0.19λ, where λ is the wavelength of light. The experiments were carried out in the microwave region to verify numerical findings, and very good agreement between the two approaches was found. The subwavelength light focusing is associated with a strong interference effect due to nonuniformly arranged scatterers and an irregular index gradient. Improving the focusing capability of optical elements by surpassing the diffraction limit of light is of paramount importance in optical imaging, lithography, data storage, and strong light-matter interaction.

Photonic crystals

Abstract: The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

Refractive index less than two: photonic nanojets yesterday, today and tomorrow [Invited]

Abstract: Materials with relatively small refractive indices (n<2), such as glass, quartz, polymers, some ceramics, etc., are the basic materials in most optical components (lenses, optical fibres, etc.). In this review, we present some of the phenomena and possible applications arising from the interaction of light with particles with a refractive index less than 2. The vast majority of the physics involved can be described with the help of the exact, analytical solution of Maxwell’s equations for spherical particles (so called Mie theory). We also discuss some other particle geometries (spheroidal, cubic, etc.) and different particle configurations (isolated or interacting) and draw an overview of the possible applications of such materials, in connection with field enhancement and super resolution nanoscopy.