Ramazan Sahin

Akdeniz University · Department of Physics

Electro-optic control of quantum dots embedded in the plasmonic nanocavities enables active tuning of photonic devices for emerging applications in Quantum optics such as quantum information processing, entanglement and ultrafast optical switching. Here, we demonstrate the coherent control of plexcitonic states in (i) an off-resonant and (ii) a res...

Control of components in integrated photonic circuits is crucial in achieving programmable devices. Operation bandwidth of a plasmonic device cannot be generally tuned once it is manufactured, especially in the visible regime. Here, we demonstrate the electrical control of such a device for extraordinary optical transmission (EOT) in the visible re...

Quantum control of integrated photonic devices has emerged as a powerful tool to overcome signal losses and obtain dynamic control over photon energies, without complex device customization. Here, we demonstrate the coherent quantum control of extraordinary optical transmission (EOT) in the visible regime by coupling plasmon resonances with a two-l...

Understanding the ultrafast processes at their natural-time scale is crucial for controlling and manipulating nanoscale optoelectronic devices under light-matter interaction. Here, we demonstrate that ultrafast plasmon resonances, attributed to the phenomenon of Extraordinary Optical Transmission (EOT), can be significantly modified by tuning the s...

Understanding the ultrafast processes at their natural-time scale is crucial for controlling and manipulating nanoscale optoelectronic devices under light-matter interaction. Here, we demonstrate that ultrafast plasmon resonances, attributed to the phenomenon of Extraordinary Optical Transmission (EOT), can be significantly modified by tuning the s...

Raman scattering signal can be enhanced through localization of incident field into sub-wavelength hot-spots through plasmonic nanostructures (surface-enhanced raman scattering—SERS). Recently, further enhancement of SERS signal via quantum objects are proposed by Postaci (Nanophotonics 7:1687, 2018) without increasing the hot-spot intensity (silen...

In this study, we present the production of silver nanoparticles in aqueous Inula Viscosa extract by the green synthesis approach at room temperature. The structural, morphological properties as well as formation kinetics of the synthesized silver nanoparticles were characterized by UV-VIS, STEM, XRD, Raman and FTIR measurements. Mono-dispersed and...

We aimed to synthesize and characterize silver nanoparticles (AgNPs) in a Inula Viscosa extract at room temperature and under different reaction conditions by green synthesis method. The green synthesis method has been getting attention in recent years due to its low cost and relatively less release of toxic substances into the environment. Inula V...

Raman scattering signal can be enhanced through localization of incident field into sub-wavelength hot-spots through plasmonic nano-structures (Surface-enhanced Raman scattering-SERS). Recently, further enhancement of SERS signal via quantum objects are proposed by [1] without increasing the hot-spot intensity (\textit{silent-enhancement}) where th...

We develop a theoretical framework describing numerical approach to explore dynamic acoustic force sensitivity using micro-cantilever array in monomodal and bimodal operations. The excitation force at the second eigenmode frequency is supplied to the micro-cantilevers in monomodal operation. Since we focus on measurement sensitivity of acoustic for...

We develop a theoretical framework describing numerical approach to explore dynamic acoustic force sensitivity using micro-cantilever array in monomodal and bimodal operations. The excitation force at second eigenmode frequency is supplied to the micro-cantilevers in monomodal operation. Since we focus on measurement sensitivity of acoustic forces...

Surface plasmon-induced nonlinear optical resonances have shown immense potential in advanced optical imaging and nonlinear photonic devices. However, the ultrashort lifetime of these intense nonlinear fields inhibits their effective use in the vast applications of quantum plasmonics. Here, we propose enhancement in the lifetime of fast decaying se...

We present a detailed analysis on measurement sensitivity of dynamic acoustic forces via numerical simulation of the micro-cantilever responses. The rectangular micro-cantilever is regarded as a point mass in the dynamic model of forced and damped harmonic oscillator. We use single- and bimodal-frequency excitation schemes for actuation of the micr...

We propose a miniaturized photonic switch, which utilizes (recently discovered) plasmon analog of index enhancement. An index is tuned via a control (auxiliary) pulse. The operation principle of the proposed device, composed of a few layers of nanorod dimers, is different than the conventional photonic switches. In the proposed device, a stop band...

Spatio-temporal control of ultrafast plasmon resonances has gained research interest in recent years because of their tremendous implications in nonlinear optics and ultrafast quantum technology. In particular, the lifetime of ultrashort plasmon oscillations has become a debatable subject in recent experimental and theoretical studies in order to f...

We present here a numerical calculation for sensitivity comparison of single- and bimodal-excitation of micro-cantilever (owing rectangular shape) on the measurement of static acoustic force. We model the micro-cantilever as a point mass in our simulations similar to forced harmonic oscillator with damping. In bimodal operation, the micro-cantileve...

Metal nanostructures support plasmon oscillations on their surfaces, which normally decay very quickly. Nevertheless, the lifetime of these oscillations can be extended near a longer lifetime particle, e.g., a molecule. We utilize this phenomenon for ultrahigh (single-molecule) resolution ultrafast apertureless (scattering) applications. We demonst...

We developed a unique model for exciton in monolayer medium with an effective dielectric constant $\epsilon_{eff}$ (in which the monolayer material is placed on a substrate such as fused silica glass or $SiO_{2}$ in experiments). Our model was based on an exact solution of the corresponding fully-covariant two-body Dirac-Coulomb type equation. For...

A recent study shows that: when a long lifetime particle is positioned near a plasmonic metal nanoparticle, lifetime of plasmon oscillations extends, but, "only" near that long-life particle [PRB 101, 035416 (2020)]. Here, we show that this phenomenon can be utilized for ultrahigh (single-molecule) resolution ultrafast apertureless (scattering) SNO...

We present a novel method for active continuous-tuning of a band gap which has the great potential to revolutionalize current photonic technologies. We study a periodic structure of x and y-aligned nanorod dimers. Refractive index of an y-polarized probe pulse can be continuously-tuned by the intensity of an x-polarized auxiliary (pump) pulse. Orde...

We present a nanosecond laser ablation of Si(111) surfaces with diffraction-free (Bessel\(J_0\)) beams. Experimental results compared with theoretical predictions show that Bessel beams give possibility of straightforward micro-structuring of Si(111). Only central spot could damage the surface provided that the laser pulse energy is in the energy r...

We demonstrate the strong coupling of a quantum dot and a graphene spherical shell coating it. Our simulations are based on solutions of three-dimensional Maxwell equations, using a boundary element method approach. Interaction between the nanostructures produces sharp hybrid modes, even when the two are off-resonant. The coupling of the light to t...

Lasers in the nanosecond pulsed regimes are relatively cheaper than ultrafast regimes but yields the larger heat-affected and ablation zone around the focal diameter. Ablation mechanism of laser in ultra-fast regime is explained totally by non-thermal modal. On the other hand, pulse duration is much longer in nanosecond regime to transfer enough en...

We present here an ultra-intense field localization at both on-resonant and off-resonant wavelengths via path interference effect in nanoscale Au Bow-tie structure with single molecule coupling. First, the physics behind the Au Bow-tie with single molecule interaction is explained. Then, path-interference effect is obtained through analysis and som...

In this work, we explore extra-ordinary-transmission (EOT) behavior where localized and propagating surface plasmon fields due to the sub-wavelength periodical holes in a relatively thick metal film (opaque) are under an interaction with two-level quantum emitters. First, the transmission properties (plasmon modes, electrical field amplitudes etc.)...

We present exact solutions of an energy spectrum of 2-interacting particles in which they seem to be relativistic fermions in 2+1 space-time dimensions. The 2x2 spinor equations of 2-interacting fermions through general central potential were separated covariantly into the relative and center of mass coordinates. First of all, the coupled first ord...

We present exact solutions of an energy spectrum of 2-interacting particles in which they seem to be relativistic fermions in 2 + 1 space-time dimensions. The 2 × 2 spinor equations of 2-interacting fermions through general central potential were separated covariantly into the relative and center of mass coordinates. First of all, the coupled first...

We present here a nanosecond laser ablation of Si(111) wafer with diffraction-free (Bessel-$J_0$) beams. First, the Axicon a conical shaped optical element for beam shaping is characterized with a visible and infrared light sources. Then, ablation profiles are obtained with Bessel beams generated for $\alpha=1^{\circ}$ and $\alpha=20^{\circ}$ base...

We investigate the optical response of a graphene spherical shell which has a semi-conducting material core through their absorption spectrum. The semi-conducting material is described by a Lorenztian expression, which approximates the optical responce of a quantum emitter. We present the tunability of the localized plasmon resonance of the graphen...

Nanosecond laser ablation of p-type Si(111) wafer is presented under an ambient, a water and a glycerin conditions. Effects of pulse energy, number of pulses and type of environment are systematically analyzed with an Optical Profilometer, a Scanning Electron Microscope and an Atomic Force Microscope. Obtained results are compared with Zemax∘-EE si...

Nanosecond laser ablation of p-type Si(111) wafer is presented under an ambient, a water and a glycerin conditions. Effects of pulse energy, number of pulses and type of environment are systematically analyzed with an Optical Profilometer, a Scanning Electron Microscope and an Atomic Force Microscope. Obtained results are compared with Zemax-EE sim...

An atomic force microscope (AFM) tip, with a few nm-thick noble metal coating, gives rise to strong electric-field at the near-field of tip apex, i.e. hot spot, when illuminated with a beam of light linearly polarized in the axial direction. This strong near-field enables resolving molecular landscape or nano-scale defects on crystal surfaces in ap...

A theoretical prediction of the propagation characteristics of Laguerre-Gaussian beams after passing through a blunt-tip axicon is presented. An ideal axicon generates theoretically perfect diffraction-free and smooth-on-axis intensity Bessel beams, while experiments and calculations show that a zeroth-order Bessel beam deviates from its perfect be...

Femtosecond lasers can provide submicron ablation resolution, making them suitable and attractive for various micro/nanofabrication applications. Laser beam shaping lends further advantages and increases the versatility of these sources. In this work, we report on the use of femtosecond laser pulses with first-order Bessel function (Bessel vortex)...

Electromagnetic wave propagation through and reflection from grating-like structures is one of the very fundamental and most studied subjects both in electromagnetics and optics. Several theoretical models and numerical solvers have been developed in order to solve this problem as efficiently and accurately as possible for different applications. I...

We report nanometer-size patterning of various thin films by femtosecond pulsed Bessel beams. Nanoslit arrays fabricated on gold films exhibit excitation of surface plasmon polaritons. We extend the approach to single-atomic-layer systems such as graphene.

The influence of beam intensity on laser ablation quality and ablation size is experimentally studied on graphene-coated silicon/silicon dioxide substrates. With an amplified femtosecond-pulsed laser system, by systematically decreasing the average power, periodic stripes with decreasing widths are ablated. Histogram analyses of the untouched and a...

We report on nanometer-scale patterning of single layer graphene on SiO2/Si substrate through femtosecond laser ablation. The pulse fluence is adjusted around the single-pulse ablation threshold of graphene. It is shown that, even though both SiO2 and Si have more absorption in the linear regime compared to graphene, the substrate can be kept intac...

Nanoslit arrays are fabricated on thin metal film coated glass slides using femtosecond laser pulses with Bessel beam profiles. The optical properties of the fabricated structures with different periodicities are characterized with transmission spectroscopy. Experimental results reveal the existence of two separate surface plasmon resonance modes o...

Femtosecond laser ablation with Bessel beam profile can yield high quality structures on metal thin films at nanoscale [1]. By adjusting the laser fluence one can control size of ablated structures. Moreover, resolution can go beyond the diffraction limit when the laser energy is adjusted around the ablation threshold [2]. Advantages of using diffr...