Browsing by Subject "Infrared devices"

Now showing 1 - 19 of 19

Open Access
Bulanıklık tespiti birikimli olasılığına dayalı kızılötesi kamera otomatik odaklanması
(IEEE, 2014-04) Çakır, Serdar; Çetin, A. Enis
Nesne iz ölçümü ve analizinde kızılötesi (KÖ) kameralar önemli bir rol oynamaktadır. Özellikle araştırma ve askeri amaçlı kullanılan bilimsel KÖ kameralarda odaklama el ile yapılmakta ve bu durum alınan ölçümün hassasiyet ve güvenilirliğini azaltmaktadır. Otomatik kamera odaklama algoritmaları imgeden çeşitli öznitelikler çıkararak en iyi odak noktası için bir ölçüt belirlemeye çalışmaktadır. Bu çalışmada, imge kalite değerlendirilmesinde kullanılan dayanaksız (referanssız) bir bulanıklık ölçütü bir takım uyarlamalardan geçirilmekte ve uyarlanan bu ölçüt KÖ kamera otomatik odaklanması problemi için önerilmektedir. Gerçekştirilen deneysel çalışmalar önerilen yöntemin KÖ kamera otomatik odaklanması probleminde başarıyla kullanılabileceğini göstermiştir.
Open Access
Differentiation and localization of target primitives using infrared sensors
(IEEE, 2002-09-10) Aytaç, Tayfun; Barshan, Billur
This study investigates the use of low-cost infrared sensors in the differentiation and localization of commonly encountered target primitives in indoor environments, such as planes, corners, edges, and cylinders. The intensity readings from such sensors are highly dependent on target location and properties in a way which cannot be represented in a simple manner, making the differentiation and localization process difficult. In this paper, we propose the use of angular intensity scans and present an algorithm to process them. This approach can determine the target type independent of its position. Once the target type is identified, its position can also be estimated. The method is verified experimentally. An average correct classification rate of 97% over all target types is achieved and targets are localized within absolute range and azimuth errors of 0.8 cm and 1.6°, respectively. The proposed method should facilitate the use of infrared sensors in mobile robot applications for differentiation and localization beyond their common usage as simple proximity sensors for object detection and collision avoidance.
Open Access
Ensemble pruning for text categorization based on data partitioning
(Springer, Berlin, Heidelberg, 2011) Toraman, Çağrı; Can, Fazlı
Ensemble methods can improve the effectiveness in text categorization. Due to computation cost of ensemble approaches there is a need for pruning ensembles. In this work we study ensemble pruning based on data partitioning. We use a ranked-based pruning approach. For this purpose base classifiers are ranked and pruned according to their accuracies in a separate validation set. We employ four data partitioning methods with four machine learning categorization algorithms. We mainly aim to examine ensemble pruning in text categorization. We conduct experiments on two text collections: Reuters-21578 and BilCat-TRT. We show that we can prune 90% of ensemble members with almost no decrease in accuracy. We demonstrate that it is possible to increase accuracy of traditional ensembling with ensemble pruning. © 2011 Springer-Verlag Berlin Heidelberg.
Open Access
High performance infrared photodetectors up to 2.8 μm wavelength based on lead selenide colloidal quantum dots
(OSA - The Optical Society, 2017) Thambidurai, M.; Jang, Y.; Shapiro, A.; Yuan, G.; Xiaonan, H.; Xuechao, Y.; Wang, Q. J.; Lifshitz, E.; Demir, Hilmi Volkan; Dang C.
The strong quantum confinement effect in lead selenide (PbSe) colloidal quantum dots (CQDs) allows to tune the bandgap of the material, covering a large spectral range from mid- to near infrared (NIR). Together with the advantages of low-cost solution processability, flexibility and easy scale-up production in comparison to conventional semiconductors especially in the mid- to near infrared range, PbSe CQDs have been a promising material for infrared optoelectronic applications. In this study, we synthesized monodisperse and high purity PbSe CQDs and then demonstrated the photodetectors working at different wavelengths up to 2.8 μm. Our high quality PbSe CQDs show clear multiple excitonic absorption peaks. PbSe CQD films of different thicknesses were deposited on interdigitated platinum electrodes by a simple drop casting technique to make the infrared photodetectors. At room temperature, the high performances of our PbSe CQD photodetectors were achieved with maximum responsivity, detectivity and external quantum efficiency of 0.96 A/W, 8.13 × 109 Jones and 78% at 5V bias. Furthermore, a series of infrared LEDs with a broad wavelength range from 1.5 μm to 3.4 μm was utilized to demonstrate the performance of our fabricated photodetectors with various PbSe CQD film thicknesses.
Open Access
Idler-efficiency-enhanced long-wave infrared beam generation using aperiodic orientation-patterned GaAs gratings
(Optical Society of America, 2016) Figen, Z. G.; Aytür, O.; Arıkan, Orhan
In this paper, we design aperiodic gratings based on orientation-patterned gallium arsenide (OP-GaAs) for converting 2.1 μm pump laser radiation into long-wave infrared (8-12 μm) in an idler-efficiency-enhanced scheme. These single OP-GaAs gratings placed in an optical parametric oscillator (OPO) or an optical parametric generator (OPG) can simultaneously phase match two optical parametric amplification (OPA) processes, OPA 1 and OPA 2. We use two design methods that allow simultaneous phase matching of two arbitrary Ï‡ 2 processes and also free adjustment of their relative strength. The first aperiodic grating design method (Method 1) relies on generating a grating structure that has domain walls located at the zeros of the summation of two cosine functions, each of which has a spatial frequency that equals one of the phase-mismatch terms of the two processes. Some of the domain walls are discarded considering the minimum domain length that is achievable in the production process. In this paper, we propose a second design method (Method 2) that relies on discretizing the crystal length with sample lengths that are much smaller than the minimum domain length and testing each sample's contribution in such a way that the sign of the nonlinearity maximizes the magnitude sum of the real and imaginary parts of the Fourier transform of the grating function at the relevant phase mismatches. Method 2 produces a similar performance as Method 1 in terms of the maximization of the height of either Fourier peak located at the relevant phase mismatch while allowing an adjustable relative height for the two peaks. To our knowledge, this is the first time that aperiodic OP-GaAs gratings have been proposed for efficient long-wave infrared beam generation based on simultaneous phase matching.
Open Access
Large area compatible broadband superabsorber surfaces in the VIS-NIR spectrum utilizing metal-insulator-metal stack and plasmonic nanoparticles
(OSA - The Optical Society, 2016) Dereshgi, S. A.; Okyay, Ali Kemal
Plasmonically enhanced absorbing structures have been emerging as strong candidates for photovoltaic (PV) devices. We investigate metal-insulator-metal (MIM) structures that are suitable for tuning spectral absorption properties by modifying layer thicknesses. We have utilized gold and silver nanoparticles to form the top metal (M) region, obtained by dewetting process compatible with large area processes. For the middle (I) and bottom (M) layers, different dielectric materials and metals are investigated. Optimum MIM designs are discussed. We experimentally demonstrate less than 10 percent reflection for most of the visible (VIS) and near infrared (NIR) spectrum. In such stacks, computational analysis shows that the bottom metal is responsible for large portion of absorption with a peak of 80 percent at 1000 nm wavelength for chromium case.
Open Access
MIMIM photodetectors using plasmonically enhanced MIM absorbers
(SPIE, 2017) Dereshgi, S. Abedini; Okyay, Ali Kemal
We demonstrate super absorbing metal-insulator-metal (MIM) stacks and MIMIM photosensitive devices operating at visible and near-infrared (VIS-NIR) spectrum, where absorbing (top) MIM and photocollecting (bottom) MIM can be optimized separately. We investigate different bottom metals in absorbing MIM with nanoparticles realized by dewetting of silver thin film on top. While gold and silver have conventionally been considered the most appropriate plasmonic absorbers, we demonstrate different absorbing metals like aluminum and specifically chromium, with its plasma frequency happening at 850 nm, as more efficient layers for absorption. Absorption in chromium hits 82 percent around 1000 nm. We provide convincing evidences by doing reflection experiment and computational simulations for absorbing MIM part. We also suggest for the first time investigating electric loss tangent of metal or coherently, surface plasmon quality factor of absorbing metals which are reliable tools for engineering different metal layers. They reveal that despite the fact that gold and silver are good plasmonic scatterers in VIS-NIR and reliable absorbers in VIS region, they are not proper choices as absorbers for NIR applications. Once the most optimum absorbing design is pointed out, we integrate it on top of another metal-insulator to form an MIMIM photodetector with tunneling photocurrent path. The final optimized sample consisting of silver - hafnium oxide - chromium - aluminum oxide - silver nanoparticles (from bottom to top) has a dark current of 7nA and a photoresponsivity peak of 0.962 mA/W at 1000 nm and a full width at half maximum of 300 nm, while applied bias is 50 mV and device areas are 300 μm x 600 μm. This photoresponse shows 70 times enhancement compared to former reported spin coated rare nanoparticle MIMIMs.
Open Access
A near-infrared range photodetector based on indium nitride nanocrystals obtained through laser ablation
(IEEE, 2014) Tekcan, B.; Alkis, S.; Alevli, M.; Dietz, N.; Ortac, B.; Bıyıklı, Necmi; Okyay, Ali Kemal
We present a proof-of-concept photodetector that is sensitive in the near-infrared (NIR) range based on InN nanocrystals. Indium nitride nanocrystals (InN-NCs) are obtained through laser ablation of a high pressure chemical vapor deposition grown indium nitride thin film and are used as optically active absorption region. InN-NCs are sandwiched between thin insulating films to reduce the electrical leakage current. Under-1 V applied bias, the recorded photoresponsivity values within 600-1100-nm wavelength range are as high as (3.05 × 10-2) mA/W. An ultrathin layer of nanocrystalline InN thin film is, therefore, a promising candidate for NIR detection in large area schemes. © 2014 IEEE.
Open Access
A new approach to search result clustering and labeling
(Springer, Berlin, Heidelberg, 2011) Türel, Anıl; Can, Fazlı
Search engines present query results as a long ordered list of web snippets divided into several pages. Post-processing of retrieval results for easier access of desired information is an important research problem. In this paper, we present a novel search result clustering approach to split the long list of documents returned by search engines into meaningfully grouped and labeled clusters. Our method emphasizes clustering quality by using cover coefficient-based and sequential k-means clustering algorithms. A cluster labeling method based on term weighting is also introduced for reflecting cluster contents. In addition, we present a new metric that employs precision and recall to assess the success of cluster labeling. We adopt a comparative strategy to derive the relative performance of the proposed method with respect to two prominent search result clustering methods: Suffix Tree Clustering and Lingo. Experimental results in the publicly available AMBIENT and ODP-239 datasets show that our method can successfully achieve both clustering and labeling tasks. © 2011 Springer-Verlag Berlin Heidelberg.
Open Access
Novel optical antenna designs of comb shaped split ring architecture for NIR and MIR enhanced field localization
(IEEE, 2014) Kılıç, Veli Tayfun; Ertürk, Vakur B.; Demir, Hilmi Volkan
We demonstrated NIR/MIR resonance behavior in optical antennas of comb-shaped split-ring resonators enabling substantially larger field enhancements than single/array of dipoles with the same side length, despite their simple architecture.
Open Access
Optically thin composite resonant absorber at the near-infrared band: A polarization independent and spectrally broadband configuration
(Optical Society of American (OSA), 2011) Boratay Alici, K.; Burak Turhan, A.; Soukoulis, C.M.; Özbay, Ekmel
We designed, fabricated, and experimentally characterized thin absorbers utilizing both electrical and magnetic impedance matching at the near-infrared regime. The absorbers consist of four main layers: a metal back plate, dielectric spacer, and two artificial layers. One of the artificial layers provides electrical resonance and the other one provides magnetic resonance yielding a polarization independent broadband perfect absorption. The structure response remains similar for the wide angle of incidence due to the sub-wavelength unit cell size of the constituting artificial layers. The design is useful for applications such as thermal photovoltaics, sensors, and camouflage. ©2011 Optical Society of America.
Open Access
Passive polarization filtering in negative curvature hollow-core fibers
(SPIE - International Society for Optical Engineering, 2023-10-05) Siddiqui, Muhammad Zain; Akosman, A. E.; Ordu, Mustafa; Yin, Shizhuo; Guo, Ruyon
A novel negative curvature hollow-core fiber (NCF) design is proposed capable of spectral and polarization filtering in the near-infrared region. The designed six-tube silica-based NCF contains nest elements in the form of suspended tubes radially anchored with a pole to the outer cladding in the vertical direction. In contrast, standard nested cladding elements without any suspension are used through the horizontal axis. This fiber configuration introduces an asymmetry in the core, which helps maintain the orthogonal X and Y polarization states in the fiber core. Pole anchors in vertically positioned tubes only give rise to the spectral filtering confinement loss profile for a vertically polarized state. Based on the geometrical optimization of the fiber, we achieved an improved birefringence on the order of 10-5 with filtered wavelength losses below 0.01 dB/km in the wavelength range of 1.4 µm to 1.7 µm. The operational bandwidth, polarization extinction ratio, filtered wavelengths, birefringence, and modulation depth loss can be tuned by optimizing the fiber parameters, including outer tube thickness, nest tube diameter, and pole dimensions. This proposed fiber design with selective transmission spectrums has untapped potential sensing capabilities in hollow-core negative curvature fibers. © 2023 SPIE. All rights reserved.
Open Access
Plasmonic gratings for enhanced near infrared sensitivity of Silicon based Schottky photodetectors
(IEEE, 2011) Polat, Kazım Gürkan; Aygun, Levent Erdal; Okyay, Ali Kemal
Schottky photodetectors have been intensively investigated due to their high speeds, low device capacitances, and sensitivity in telecommunication standard bands, in the 0.8μm to 1.5μm wavelength range. Due to extreme cost advantage of Silicon over compound semiconductors, and seamless integration with VLSI circuits, metal-Silicon Schottky photodetectors are attractive low cost alternatives to InGaAs technology. However, efficiencies of Schottky type photodetectors are limited due to thin absorption region. Previous efforts such as resonant cavities increase the sensitivity using optical techniques, however their integration with VLSI circuits is difficult. Therefore, there is a need for increasing Schottky detector sensitivity, in a VLSI compatible fashion. To address this problem, we design plasmonic grating structures to increase light absorption at the metal-Silicon Schottky interface. There are earlier reports of plasmonic structures to increase Schottky photodetector sensitivity, with a renowned interest in the utilization of plasmonic effects to improve the absorption characteristics of metal-semiconductor interfaces. In this work, we report the design, fabrication and characterization of Gold-Silicon Schottky photodetectors with enhanced absorption in the near infrared region. © 2011 IEEE.
Open Access
Postdeposition annealing on RF-sputtered SrTiO3 thin films
(AVS Science and Technology Society, 2017) Bayrak, T.; Kizir,S.; Kahveci, E.; Bıyıklı, N.; Goldenberg, E.
Understanding of structural, optical, and electrical properties of thin films are very important for a reliable device performance. In the present work, the effect of postdeposition annealing on stoichiometric SrTiO3 (STO) thin films grown by radio frequency magnetron sputtering at room temperature on p-type Si (100) and quartz substrates were studied. Highly transparent and well adhered thin films were obtained in visible and near infrared regions. As-deposited films were amorphous, while nanocrystalline and polycrystalline phases of the STO thin films formed as a function of annealing temperature. Films annealed at 300 ï¿½C showed nanocrystallinity with some amorphous phase. Crystallization started after 15 min annealing at 700 ï¿½C, and further improved for films annealed at 800 ï¿½C. However, crystallinity reduced for films which were annealed at 900 ï¿½C. The optical and electrical properties of STO thin films affected by postdeposition annealing at 800 ï¿½C: Eg values decreased from 4.50 to 4.18 eV, n(λ) values (at 550 nm) increased from 1.81 to 2.16. The surface roughness increased with the annealing temperature due to the increased crystallite size, densification and following void formation which can be seen from the scanning electron microscopy images. The highest dielectric constants (46 at 100 kHz) observed for films annealed at 800 ï¿½C; however, it was lower for 300 ï¿½C annealed (25 at 100 kHz) and as-deposited (7 at 100 kHz) STO films having ∼80 nm thickness.
Open Access
Range estimation using simple infrared sensors without prior knowledge of surface parameters
(IEEE, 2004) Yüzbaşıoğlu, Çağrı; Barshan, Billur
This paper describes a new method for range estimation using low-cost infrared sensors. The intensity data obtained with infrared sensors depends highly on the surface properties and the configuration of the sensors and the surface. Therefore, in many of the related studies, either the properties of the surface are determined first or certain assumptions about the surface are made in order to calculate the distance and the orientation of the surface relative to the sensors. In this paper, we propose a novel method for position estimation of surfaces with infrared sensors without the need to determine the surface properties first. The method is verified experimentally with planar surfaces covered with white paper, wooden block, bubbled packing material, white styrofoam, blue and brown cardboard. The overall absolute mean error in the range estimates has been calculated as 0.21 cm in the range from 12.5 to 45 cm. The results obtained demonstrate that infrared sensors can be easily used for localization to an unexpectedly high accuracy without prior knowledge of the surface parameters.
Open Access
Remote-controlled release of singlet oxygen by the plasmonic heating of endoperoxide-modified gold nanorods: towards a paradigm change in photodynamic therapy
(Wiley-VCH Verlag, 2016) Kolemen, S.; Ozdemir, T.; Lee, D.; Kim, G. M.; Karatas, T.; Yoon, J.; Akkaya, E. U.
The photodynamic therapy of cancer is contingent upon the sustained generation of singlet oxygen in the tumor region. However, tumors of the most metastatic cancer types develop a region of severe hypoxia, which puts them beyond the reach of most therapeutic protocols. More troublesome, photodynamic action generates acute hypoxia as the process itself diminishes cellular oxygen reserves, which makes it a self-limiting method. Herein, we describe a new concept that could eventually lead to a change in the 100 year old paradigm of photodynamic therapy and potentially offer solutions to some of the lingering problems. When gold nanorods with tethered endoperoxides are irradiated at 808 nm, the endoperoxides undergo thermal cycloreversion, resulting in the generation of singlet oxygen. We demonstrate that the amount of singlet oxygen produced in this way is sufficient for triggering apoptosis in cell cultures. EPT sees the light: When gold nanorods with tethered endoperoxides are irradiated with near-infrared light, the endoperoxides undergo thermal cycloreversion, resulting in the generation of singlet oxygen. The amount of singlet oxygen generated by these nanocomposites is sufficient for triggering apoptosis in cell cultures.
Open Access
A robust system for counting people using an infrared sensor and a camera
(Elsevier BV, 2015) Erden, F.; Alkar, A. Z.; Çetin, A. Enis
In this paper, a multi-modal solution to the people counting problem in a given area is described. The multi-modal system consists of a differential pyro-electric infrared (PIR) sensor and a camera. Faces in the surveillance area are detected by the camera with the aim of counting people using cascaded AdaBoost classifiers. Due to the imprecise results produced by the camera-only system, an additional differential PIR sensor is integrated to the camera. Two types of human motion: (i) entry to and exit from the surveillance area and (ii) ordinary activities in that area are distinguished by the PIR sensor using a Markovian decision algorithm. The wavelet transform of the continuous-time real-valued signal received from the PIR sensor circuit is used for feature extraction from the sensor signal. Wavelet parameters are then fed to a set of Markov models representing the two motion classes. The affiliation of a test signal is decided as the class of the model yielding higher probability. People counting results produced by the camera are then corrected by utilizing the additional information obtained from the PIR sensor signal analysis. With the proof of concept built, it is shown that the multi-modal system can reduce false alarms of the camera-only system and determines the number of people watching a TV set in a more robust manner.
Open Access
Thermally switchable, bifunctional, scalable, mid-infrared metasurfaces with VO2 grids capable of versatile polarization manipulation and asymmetric transmission
(Optica Publishing Group (formerly OSA), 2022-12-01) Serebryannikov, Andriy E.; Lakhtakia, Akhlesh; Özbay, Ekmel
We conceptualized three-array scalable bifunctional metasurfaces comprising only three thin strip grids and numerically determined their characteristics in the mid-infrared spectral regime for switchable operation scenarios involving polarization manipulation and related diodelike asymmetric transmission (AT) as one of two functionalities. A few or all of the grids were taken to be made of VO2, a bifunctionality-enabling phase-change material; there are no layers and/or meta-atoms comprising simultaneously both metal and VO2. For each proposed metasurface, two effective structures and, therefore, two different functionalities exist, corresponding to the metallic and insulating phases of VO2. The achieved scenarios of functionality switching significantly depend on the way in which VO2 is incorporated into the metasurface. Switchable bands of polarization manipulation are up to 40 THz wide. The AT band can be modulated when Fabry-Perot (anti-) resonances come into play. Besides, transmission regimes with the cross-polarized component insensitive to VO2 phase change are possible, as well as the ones with all co- and cross-polarized components having the same magnitude for both linear polarizations of the incident wave. © 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
Open Access
Ultra-low-cost near-infrared photodetectors on silicon
(SPIE, 2015-02) Nazirzadeh, M. Amin; Atar, Fatih B.; Turgut, B. Berkan; Okyay, Ali Kemal
We demonstrate Silicon-only near-infrared (NIR) photodetectors (sensitive up to 2000 nm) that meet large-scale ultralow-cost fabrication requirements. For the detection of infrared photons, we use metal nanoislands that form Schottky contact with Silicon. NIR photons excite plasmon resonances at metal nanoislands and plasmons decay into highly energetic charge carriers (hot electrons). These hot electrons get injected into Silicon (internal photoemission), resulting in photocurrent. Several groups have studied plasmonic nanoantennas using high resolution lithography techniques. In this work, we make use of randomly formed nanoislands for broad-band photoresponse at NIR wavelengths. We observe photoresponse up to 2000 nm wavelength with low dark current density about 50 pA/μm2. The devices exhibit photoresponsivity values as high as 2 mA/W and 600 μA/W at 1.3 μm and 1.55 μm wavelengths, respectively. Thin metal layer was deposited on low-doped n-type Silicon wafer. Rapid thermal annealing results in surface reconstruction of the metal layer into nanoislands. Annealing conditions control the average size of the nanoislands and photoresponse of the devices. An Al-doped Zinc Oxide (AZO) layer was deposited on the nanoislands using thermal atomic layer deposition (ALD) technique to acts as a transparent conductive oxide (TCO) and patterned using photolithography. AZO film creates electrical connection between the nanoislands and also makes a heterojunction to Silicon. Simple and scalable fabrication on Si substrates without the need for any sub-micron lithography or high temperature epitaxy process make these devices good candidates for ultra-low-cost broad-band NIR imaging and spectroscopy applications. © 2015 SPIE.