A. Karatutlu

UNAM-Institute of Materials Science and Nanotechnology · UNAM-Institute of Materials Science and Nanotechnology

Fabry-Perot (FP) optical fiber sensors are reported to be highly sensitive for detecting various physical, chemical, and biological objects. In this study, an FP-based Phase Shifted Bragg-Grating Lab-on-Fiber (PSBG-LOF) is presented to determine ultralow glucose concentrations in liquids by using a novel PSBG at the end facet of a single-mode fiber...

Optical tunability and repeatability are essential in fabricating optoelectronic devices from waveguides to Bragg gratings (BGs) for high-energy, high-power, mode-locking, and sensing applications. For this purpose, a controlled adjustment in the optical properties, including the refractive index of the deposited nanolayers, becomes critical. This...

Ytterbium (Yb)-doped optical fibers are mainly used in the fiber laser resonator and amplifier systems. These systems have been widely utilized for applications in air and space, the defense industry, and the medical field. Particularly for the applications yielding operation in harsh environments consisting of radiation, it is essential to determi...

Different applications, including interferometers, gyroscopes, and frequency combs, require a single polarized light transmission by maintaining this property against the environmental perturbation. As a new type of polarization-maintaining (PM) fiber, a biaxial PM fiber was fabricated over 30 dB of high polarization extinction ratio (PER) values a...

Fiber lasers are one of the most preferred of today's efficient coherent light sources in many application areas with their advantages such as stability, compactness, robustness, diffraction-limited beam quality, large available bandwidth, tuneability, and independence from alignment [1]. With the technological and material-based advances in fiber...

Yb-doped optical fibers are mainly used in the fiber laser resonator and amplifiers systems [1, 2]. Thus, these systems have widely usage area for applications of space environment, defense industry, laser defense systems, and medical applications, etc [3, 4]. In these applications, it is important to determine the radiation resistance of the Yb-do...

Abstract Reducing the distance between the fluorescence molecules and noble metal (resonant) nanostructures is known to advance the process of electromagnetic coupling and energy transfer, which in return yields fluorescence enhancement particularly exploited for improved biomedical applications. In this study, Au-capped Si nanowhiskers (NWs) at va...

Cladding light strippers are vital and one of the critical components for high-power fiber laser applications. In thisstudy, we show the first studies of the formation mechanisms and optimum conditions of a cladding light stripper(CLS) device using a buffered oxide etchant by a combined method of stain (wet) etching and vapor phase etching.This hig...

The first attempts of implanting Ge nanoparticles (Ge NPs) inside iron filled CNTs (IF‐CNTs) by a subsequent use of the bench top colloidal synthesis and chemical vapor deposition (CVD) approach is shown. Ge NPs are colloidally synthesized (with a 3.8 ± 0.6 nm in size) before the deposition. The hybrid Ge NPs/IF‐CNTs structure and morphology are ch...

We presented the potential of existing approaches and contributions of our group in preparation of cladding light strippers including chemical etching, polymer coatings, soft-metal coatings and laser processing.

Carbon is an essential element in human life and recently becoming technologically prominent due to the emerging field of “Carbononics”. We demonstrate organic carbon quantum dots (qdots) containing nitrile bonded (CN bond) d-glucoselike traces in various sizes obtained from wheat flour to be promising for imaging applications and to possess a rela...

In this study, the size selective deposition of SiGe nanoislands is demonstrated to be possible only in Si nanopits using a molecular beam epitaxy (MBE) system. The depth of the etched Si substrate prepared by Ar⁺ plasma etching just before the deposition seems to be playing a role in the selectivity of keeping the SiGe nanoislands only inside the...

Nanoparticles less than 100nm in size have attracted significant interest over the past 20 years due to their unique properties led by quantum size effect. This chapter evaluates the synthesis methods in liquid phase conducted under operation in high/room temperature and at vacuum/atmospheric environment for nanoparticles and nanostructured materia...

Nanoparticles (NPs) and nanostructured materials exhibit shape- and size-dependent properties that are desired for a wide variety of applications, such as catalysis, sensing, drug delivery, energy production, and storage. In view of this, it is essential to produce well-defined NPs and nanostructures with desired characteristics, to understand thei...

SiGe nanoislands were grown by Molecular Beam Epitaxy (MBE) method on Si (100) substrates with comparative growth parameters such as annealing temperature, top Ge content and layer-by-layer annealing (LBLA). XRD and Raman data suggest that annealing temperature, top Ge content and layer-by-layer annealing (LBLA) can overall give a control not only...

In this research paper, light emitting porous silicon (Lep-Si) samples were fabricated by a surfactant-mediated chemical stain etching solution in order to form homogenous luminescent nanostructures at room temperature. As an industrially important solvent, decalin (decahydronaphtalene) was used as a surfactant in the HF/HNO3 solutions in order to...

In single molecule localisation super-resolution microscopy the need for repeated image capture limits the imaging speed, while the size of fluorescence probes limits the possible theoretical localisation resolution. Here, we demonstrated a spectral imaging based super-resolution approach by separating the overlapping diffraction spots into several...

We examined sensitivity of the x-ray absorption near edge structure (XANES) to the local atomic arrangements in amorphous GaSb and nanoscale Ge. We demonstrate that XANES can be reliably used to obtain information about the local symmetry in these systems where lack of periodicity precludes the use of powerful diffraction methods. We used well-stud...

The sensitivity of X-ray absorption near-edge structure (XANES) to the local symmetry has been investigated in small (∼4 nm) matrix-free Ge quantum dots. The FDMNES package was used to calculate the theoretical XANES spectra that were compared with the experimental data of as-prepared and annealed nanoparticles. It was found that XANES data for an...

In this study, with the aid of Raman measurements, we have observed transformations in small (∼3 nm and ∼10 nm) free-standing Genanoparticles under laser light exposure. The nanoparticles were obtained by the chemical stain etching of a monocrystalline Ge wafer and of Gepowder and by colloidal synthesis route. We found that the transformation path...

In this paper, we show studies of Multitaper spectrum estimation techniques to obtain the Mel-frequency cepstral coefficients (MFCCs) for source microphone identification systems. In the previous works, MFCCs were computed commonly from a single windowed (Hamming) DFT spectrum for source microphone identification. Emphasis on Multitaper MFCC featur...

Over the last two decades it has been demonstrated that size effects have significant consequences for the atomic arrangements and phase behaviour of matter under extreme pressure. Furthermore, it has been shown that understanding of how size affects critical pressure-temperature conditions provides vital guidance in the search for materials with n...

We investigated the sensitivity of x-ray absorption near-edge structure (XANES) to the atomic structure of small (~ 4 nm) matrix-free Ge quantum dots. FDMNES package was used to calculate the theoretical XANES spectra that were compared to the experimental data of as-prepared and annealed nanoparticles. We found that XANES data for as-prepared samp...

Parkinson's disease (PD) is a neurological disorder which is diagnosed through clinical examinations and observations rated on Unified Parkinson's disease Rating Scale (UPDRS). However, in the earlier stages of the disease, this approach might be inconclusive and result in misdiagnosis. Therefore, expert systems are needed to increase the detection...

Free-standing Ge quantum dots around 3 nm in size were synthesized using a bench-top colloidal method and suspended in water and ethanol. In the ethanol solution, the photoluminescence of the Ge quantum dots was observed between 650 and 800 nm. Structural and optical properties of these colloidal Ge quantum dots were investigated by utilizing X-ray...

The structure of small (2-5 nm) Ge quantum dots prepared by the colloidal synthesis route is examined. Samples were synthesized using either GeO2 or GeCl4 as precursor. As-prepared samples were further annealed under Ar or H2/Ar atmosphere at different temperatures in order to understand the effect of annealing on their structure. It was found that...

TWe used a combination of optically-detected x-ray absorption spectroscopy with molecular dynamics simulations to explore the origins of light emission in small (5 nm to 9 nm) Ge nanoparticles. Two sets of nanoparticles were studied, with oxygen and hydrogen terminated surfaces. We show that optically-detected x-ray absorption spectroscopy shows su...

Nano-particles of different materials including II-VI (ZnS, ZnO, etc.), III-V (AlN, GaN, etc.) and IV (Si, Ge, etc.) have been applied widely because of their superb optical-electrical properties. More importantly, the size & structure-dependent character of their physical properties due to the quantum confinement effect attracted much research int...

The source of visible luminescence from Ge nanocrystalline materials has been attributed to various phenomena such as the quantum confinement effect, surface contributions, and so on. In order to understand the origin of this light emission we have performed extended x-ray absorption fine structure (EXAFS) and optically-detected x-ray absorption sp...