713 research outputs found
Novel Silicon Nanophotonic Structures for Ultra-compact Integrated Lab-on-a-chip Sensing
No full textProfesssor Ali Adibi from the School of Electrical and Computer Engineering presented a lecture at the Nano@Tech Meeting on March 11, 2008 at 12 noon in room 102 of the MiRC buildingRuntime: 60:36 minutesThe development of ultra-compact and sensitive sensing structures with minimal sample requirement for accurate sensing have been of great recent interest for multiple applications including bio and environmental sensing, chemical agent detection, and bio- threat detection. With recent advancement in the development of design and fabrication tools for photonic nanostructures, integrated photonic platforms are a strong candidate for the development of such sensing structures.
In this talk, Prof. Ali Adibi first presented the requirements for the development of photonic lab-on-a-chip sensing structures. Then he explained how these requirements are met by two recent developments in our group in the area of silicon photonics, i.e., ultra-high Q micro-resonators, and ultra-compact photonic crystal on-chip spectrometers with orders of magnitude smaller size compared to the other implementations with the same performance. These spectrometers are enabled by dispersion engineering in photonic crystal to simultaneously achieve the superprism effect, negative diffraction, and negative refraction. Details of the design of such structures along with their experimental demonstrations will be presented
Controlling group velocity in rectangular-lattice photonic crystal waveguides
No full textA method for controlling the dispersion and thus group velocity of guided modes in photonic crystal (PC) waveguides using bi- and quasi-periodic lattices is presented. Rectangular lattice photonic crystals are proposed as possible candidates for implementing such control. However, these structures, and generally all bi-periodic lattices, develop undesirable characteristics as the perfect square lattice is perturbed. Thus, quasi-periodic photonic crystals, which have been shown to be promising in selective mode engineering, were examined next. A possible scheme for engineering of a single mode PC waveguide with guiding through the entire bandgap is presented
Proceedings of SPIE: Wavelength-resolved Purcell enhancement of PbS/CdS quantum dots measured on a chip-based platform
No full textFuture quantum optical networks will require an integrated solution to multiplex suitable sources and detectors on a low-loss platform. Here we combined superconducting single-photon detectors with colloidal PbS/CdS quantum dots (QDs) and low-loss silicon nitride passive photonic components to show their combined operation at cryogenic temperatures. Using a planar concave grating spectrometer, we performed wavelength-resolved measurements of the photoluminescence decay of QDs, which were deterministically placed in the gap of plasmonic antennas, in order to improve their emission rate. We observed a Purcell enhancement matching the antenna simulations, with a concurrent increase of the count rate on the superconducting detectors.ImPhys/Optic
Hybrid Material and Device Platforms for Reconfigurable Integrated Nanophotonics
No full textPresented on November 27, 2018 at 12:00 p.m.-1:00 p.m. in the Marcus Nanotechnology Building, Room 1117-1118, Georgia Tech.Ali Adibi is the director of Bio and Environmental Sensing Technologies (BEST) and a professor and Joseph M. Pettit chair in the School of Electrical and Computer Engineering, Georgia Institute of Technology. His research group has pioneered several structures in the field of integrated nanophotonics for both information processing and sensing. He is the author of more than 150 journal papers and 400 conference papers. He is the editor-in-chief of the Journal of Nanophotonics, and the nanophotonic program track chair of the Photonics West meeting. He is the recipient of several awards including Presidential Early Career Award for Scientists and Engineers, Packard Fellowship, NSF CAREER Award, and the SPIE Technology Achievement Award. He is also a fellow of OSA, SPIE, and AAAS.Runtime: 51:02 minutesThe development of ultra-compact integrated nanophotonic structures for communications, sensing, and signal processing has been of great interest lately. Recent progress in the development of miniaturized high-Q microresonators has resulted in orders of magnitude reduction in the size of functional integrated photonic structures. The possibility of low-power tuning of the resonance features in these structures has made the formation of reconfigurable photonic structures possible. Among existing CMOS-compatible substrates, silicon (Si) and silicon nitride (SiN) have been used the most. Despite impressive progress in Si-based and SiN-based integrated photonics, neither substrate alone can be used for practical applications. Si (despite its good reconfigurability) suffers from strong nonlinear effects (especially at high light intensities) and relatively large free-carrier loss while SiN (with one order of magnitude lower loss and lower nonlinearity compared to Si) is very hard to tune. Thus, a reliable material system that combines ultra-loss-loss and high power handling with efficient and fast reconfigurability is of high demand in integrated nanophotonics. In this talk, the recent achievements in the development and optimization of hybrid multi-layer CMOS-compatible material systems (e.g., SiN/Si, multi-layer Si/SiO2, etc.) to address all the practical requirements of ultra-fast and ultra-compact integrated photonic structures will be discussed. Using these hybrid material systems, a series of ultra-compact and high-performance reconfigurable photonic devices and subsystems that are formed by using high Q resonators will be demonstrated. The use of these devices and subsystems for realization of densely-integrated reconfigurable photonic chips for signal processing and sensing applications will be discussed
Using an Explicit Teamwork Model and Learning in RoboCup: An Extended Abstract
No full textStacy Marsella, Jafar Adibi, Yaser Al-Onaizan, Ali Erdem, Randall Hill Gal A. Kaminka, Zhun Qiu, Milind Tambe Information Sciences Institute and Computer Science Department University of Southern California 4676 AdmiraltyWay, Marina del Rey, CA 90292, USA [email protected] 1 Introduction The RoboCup research initiative has established synthetic and robotic soccer as testbeds for pursuing researchchallenges in Arti#cial Intelligence and robotics. This extended abstract focuses on teamwork and learning, two of the multiagent researchchallenges highlighted in RoboCup. To address the challenge of teamwork, we discuss the use of a domain-independent explicit model of teamwork, and an explicit representation of team plans and goals. We also discuss the application of agent learning in RoboCup. The vehicle for our researchinvestigations in RoboCup is ISIS #ISI Synthetic#, a team of synthetic soccer-players that successfully participated in the simulation league of RoboCup'97, by..
Normal bladder wall thickness measurement in healthy Iranian children, a cross-sectional study
No full textBackground: Normal bladder function is necessary for micturition. Many causes such as urinary tract infection, bladder outlet obstruction, and neuropathic bladder can influence bladder wall thickness (BWT).This study was designed to determine normal BWT in Iranian children.
Materials and Methods: This was a cross-sectional study done in Isfahan in 2012 comprising 82 children aged 2-14 years without any urinary complaint. We measured thickness of posterior and lateral walls of the bladder in all children. Mean bladder wall thickness (MBWT) and mean bladder volume (BV) were also calculated.
Results: In this study, we included 82 children (40 boys and 42 girls). Patients′ mean age was 6.43 ± 2.89 years, mean weight was 21.32 ± 8.40 kg, mean height was 111.57 ± 20.51 cm, and mean Body Mass Index was 17.12 ± 4.93. Mean lateral bladder wall thickness (LBWT) was 1.75 ± 0.32 mm and mean posterior bladder wall thickness (PBWT) was 1.59 ± 0.34 mm. Mean BV was 111.65 ± 72.11 ml and MBWT was 1.67 ± 0.28 mm. BVW all Index (BVWI) was 1249.05 ± 701.67.
Conclusions: LBWT was1.75 ± 0.32 mm and PBWT was 1.59 ± 0.34 mm
Change in functional bowel symptoms after prostatectomy: A case-control study
No full textBackground: Irritable bowel syndrome (IBS) is a chronic functional bowel disorder that up to 20% of the population is suffering from it. Also benign prostatic hyperplasia (BPH) is a common problem that approximately 90 percent of men may be affected by this condition until the eighth decade of their life. Prostatectomy as a surgery and pelvic intervention can cause IBS.
Methods: It was a case-control study including 66 patients in 2 case groups and 66 patients in 2 control groups. Case groups were patients who underwent open prostatectomy and transurethral resection of the prostate (TURP) and control groups were patients who were candidate for prostatectomy.
Results: Ten patients in case groups and five patients in control groups had IBS. There was no significant difference in IBS between control and case groups (p = 0.117).
Conclusions: This is the first forward study regarding bowel symptom changes following prostatectomy. The main positive finding of this study is that open prostatectomy was followed by significant increase in diarrhea and bowel habit alternation associated with onset of abdominal pain. Specifically the change was found after open operation but not after TURP. Prostatectomy whether in form of open or transurethral may cause onset of abdominal discomfort and bowel habit change
Selective Growth of B- and C-doped SiGe Layers in Unprocessed and Recessed Si Openings for pMOSFET Application
No full textThis work presents pattern dependency of selective epitaxial growth of boron- or carbon-doped SiGe layers in recessed or unprocessed openings. The layer profile and quality of epi-layers were found to be dependent on chip layout and the growth parameters. Carbon- and boron-doping compensated the strain in SiGe layers and when both dopants are introduced the strain reduction was additive. The incorporation of boron and carbon in SiGe matrix showed to be a competitive action. The concentration of carbon decreased when the boron amount increased in SiGe layers with higher Ge content
Nanophotonic design for 2D and quantum materials
No full textDesign of the resonant optical response of ultrathin two-dimensional materials and heterostructures is enabling scientific exploration of new materials phenomena. As an example, demonstrate near-unity, broadband absorbing optoelectronic devices using sub-15 nm thick transition metal dichalcogenides (TMDCs) of molybdenum andtungsten as van der Waals semiconductor active layers. Specifically, we report that near-unity light absorption is possible in extremely thin (<15 nm) van der Waals semiconductor structures by coupling to strongly damped optical modes of semiconductor/metal heterostructures. We further fabricate Schottky junction devices using these highly absorbing heterostructures and characterize their optoelectronic performance. Our work addresses one of the key criteria to enable TMDCs as potential candidates to achieve high optoelectronic efficiency. We also report mid-infrared spectroscopy measurements of an electrostatically gated topological insulator, in which we observe several percent modulation of transmittance and reflectance of (Bi_(1-x)Sb_x)_2Te_3 films as gating shifts the Fermi level. Infrared transmittance measurements of gated (B_(i1-x)Sb_x)_2Te_3 films were enabled by use of an epitaxial lift-off method for large-area transfer of TI films from the infrared-absorbing SrTiO_3 growth substrates to thermal oxidized silicon substrates. We combine these optical experiments with transport measurements and angle-resolved photoemission spectroscopy to identify the observed spectral modulation as a gate-driven transfer of spectral weight between both bulk and topological surface channels and interband and intraband channels. We develop a model for the complex permittivity of gated (Bi_(1-x)Sb_x)_2Te_3, and find a good match to our experimental data. These results open the path for layered topological insulator materials as a new candidate for tunable infrared optics and highlight the possibility of switching topological optoelectronic phenomena between bulk and spin-polarized surface regimes
Transmission and reflection features of all-dielectrics metasurfaces with electric and magnetic resonances
No full textThe effective multipole decomposition approach is applied to study the optical features of the silicon metasurface in the near-infrared. The spectral regions of perfect transmission and reflection have been analyzed using the Cartesian multipole decomposition. It is shown that transmission peaks appear due to the mutual interaction of multipole moments up to the third order, while reflection peaks are due to the dominant contribution of one of the multipole moments. The results of this work can be broadly applied to design novel metasurfaces, sensors, and optical filters. © 2019 SPIE
- …
