Bucharest, Romania
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Tudor R.,Institute for Microtechnology | Tudor R.,University of Bucharest | Mihailescu M.,Polytechnic University of Bucharest | Kusko C.,Institute for Microtechnology | And 3 more authors.
Optics Communications | Year: 2016

We present a method for spatially separated detection of multiple orbital angular momentum (OAM) states, simultaneous. The starting point is the generation of axially superposed Laguerre-Gauss beams, carrying multiple OAM states using a single computer generated hologram. The information contained in the OAM superposition is transferred to the first diffraction order and is detected at the receiver with a reading mask, which contains two perpendicular superposed fork-like holograms, ensuring the spatial separation of the OAM states. The dynamic of the process is studied in terms of the number of generated OAM states and the constructive parameters values. The experimental investigations use an optical arrangement based on a spatial light modulator in the transmitter unit and an amplitude mask in the receiver unit. This proof of concept experiment demonstrates the possibility of simultaneously detection of multiple OAM states in points located at different coordinates, controlled through the design of the holograms and shows the capability of our proposed method to increase the capacity of free-space optical communication channels. © 2016 Published by Elsevier B.V.


Tudor R.,Institute for Microtechnology | Tudor R.,University of Bucharest | Mihailescu M.,Polytechnic University of Bucharest | Paun I.A.,Polytechnic University of Bucharest | And 3 more authors.
Proceedings of the Romanian Academy Series A - Mathematics Physics Technical Sciences Information Science | Year: 2016

We analyzed the intensity distribution resulted from the axial superposition of two Laguerre-Gauss beams. It is found that the intensity spatial distribution can be transformed from interference patterns with uniform maxima and round holes or radial petals, to one consisting of separated rings, by simply changing of the interrelations between constructive parameters. The propagation robustness of two Laguerre-Gauss beam superposition is investigated for different ranges of the constructive parameter values using experimental and simulation results. Combinations of different optical angular momentum states can be obtained, transmitted and read, with almost the same efficiency in the detection process.


Orthner M.P.,University of Utah | Buetefisch S.,Institute for Microtechnology | Magda J.,University of Utah | Rieth L.W.,University of Utah | Solzbacher F.,University of Utah
Sensors and Actuators, A: Physical | Year: 2010

Hydrogels have been demonstrated to swell in response to a number of external stimuli including pH, CO2, glucose, and ionic strength making them useful for detection of metabolic analytes. To measure hydrogel swelling pressure, we have fabricated and tested novel perforated diaphragm piezoresistive pressure sensor arrays that couple the pressure sensing diaphragm with a perforated semi-permeable membrane. The 2 × 2 arrays measure approximately 3 × 5 mm2 and consist of four square sensing diaphragms with widths of 1.0, 1.25, and 1.5 mm used to measure full scale pressures of 50, 25, and 5 kPa, respectively. An optimized geometry of micro pores was etched in silicon diaphragm to allow analyte diffusion into the sensor cavity where the hydrogel material is located. The 14-step front side wafer process was carried out by a commercial foundry service (MSF, Frankfurt (Oder), Germany) and diaphragm pores were created using combination of potassium hydroxide (KOH) etching and deep reactive ion etching (DRIE). Sensor characterization was performed (without the use of hydrogels) using a custom bulge testing apparatus that simultaneously measured deflection, pressure, and electrical output. Test results are used to quantify the sensor sensitivity and demonstrate proof-of-concept. Simulations showed that the sensitivity was slightly improved for the perforated diaphragm designs while empirical electrical characterization showed that the perforated diaphragm sensors were slightly less sensitive than solid diaphragm sensors. This discrepancy is believed to be due to the influence of compressive stress found within passivation layers and poor etching uniformity. The new perforated diaphragm sensors were fully functional with sensitivities ranging from 23 to 252 μV/V-kPa (FSO = 5-80 mV), and show a higher nonlinearity at elevated pressures than identical sensors with solid diaphragms. Sensors (1.5 × 1.5 mm2) with perforated diaphragms (pores = 40 μm) have a nonlinearity of approximately 10% while for the identical solid diaphragm sensor it was roughly 3% over the entire 200 kPa range. This is the first time piezoresistive pressure sensors with integrated diffusion pores for detection of hydrogel swelling pressure have been fabricated and tested. © 2010 Elsevier B.V.


Kilani M.I.,King Faisal University | Kilani M.I.,University of Jordan | Al Halhouli A.T.,Institute for Microtechnology | Buttgenbach S.,Institute for Microtechnology
Nanoscale and Microscale Thermophysical Engineering | Year: 2011

The article presents analytical and numerical computational fluid dynamics (CFD) simulations of the flow performance in a newly introduced ferrofluidic magnetic micropump, with the purpose of estimating the stress distribution in its flow field. Analytical expressions were developed for the shear stress generated at the upper and lower walls of the pump's channel in terms of dimensionless parameters by solving the Navier-Stokes equation in cylindrical coordinates. CFD simulations have demonstrated that the shear stress is small in the majority of the pump's channel and assume significant values only in narrow strips near the walls. The analytical predictions were compared with those obtained from CFD and were found to be in very good agreement for h/w → 0 . For larger aspect ratios, the CFD predictions were found to be lower than the analytical predications. The analytical estimates provide an upper limit on the shear stress and may be used reliably for a conservative estimate of the stress. Copyright © Taylor & Francis Group, LLC.


Al-Halhouli A.T.,Institute for Microtechnology
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2010

In this work, the concept of recently introduced electromagnetic pump has been presented. This pump has been proposed for pumping biomedical fluids carrying particles sensitive to shear stresses. Its working concept depends on controlling the rotation of two pistons placed in a circular channel in opposing polarity under the influence of a moving electromagnetic field. Analytical and numerical investigations on the effect of pump geometrical parameters on shear stresses at different boundary conditions are performed. The geometrical parameters include: channel aspect ratio (channel width to height) and channel radius ratio (inner to outer radius). Non-dimensional simple analytical shear stress expressions that are valid for a wide range of geometrical design parameters and variety of fluids are derived. CFD simulations have been used to verify the analytical expressions within the range of studied parameters. Obtained results showed that the analytical models predict the wall maximum shear stresses with an error less than 5% for w / h ≤1.0 at high radius ratios and with an error less than10% for Ri/Ro ≥ 0.3. These results help the designer in fabricating the micropump to be suitable for biomedical applications, where saving the particles carried in fluids from damage is of high importance. © 2010 SPIE.

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