Search for: optical-design
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    Design and fabrication of photonic crystal nano-beam resonator: transmission line model

    , Article Journal of Lightwave Technology ; Volume 32, Issue 1 , 14 November 2013 , Pages 91-98 Miri, M ; Sodagar, M ; Mehrany, K ; Eftekhar, A. A ; Adibi, A ; Rashidian, B ; Sharif University of Technology
    We present a new method for modeling and design of photonic crystal nano-beam resonators (PCNBRs) based on cascaded transmission lines. The proposed model provides an accurate estimate of the PCNBRs properties such as resonance wavelength and quality factor (Q) with much smaller computation cost as compared to the brute-force numerical methods. Furthermore, we have developed a straightforward technique for the design of high-Q PCNBRs based on resonance modes with Gaussian electromagnetic field profiles. The results obtained by using the proposed transmission line model are compared against numerical and experimental results and the accuracy of the model is verified. The proposed model... 

    X-ray powder diffraction beamline for iranian light source facility

    , Article IPAC 2013: Proceedings of the 4th International Particle Accelerator Conference, Shanghai ; May , 2013 , Pages 130-132 ; 9783954501229 (ISBN) Khosroabadi, H ; Azhir, A. G ; Amiri, S ; Ghasem, H ; Asian Committee for Future Accelerators (ACFA); American Physical Society Division of Physics of Beams (APS-DPB); Chinese Academy of Sciences (CAS); European Physical Society Accelerator Group (EPS-AG) ; Sharif University of Technology
    X-ray Powder Diffraction beamline is one of the first priorities of Iranian Light Source Facility day-onebeamlines. This beamline will cover the research requirements of scientific community in the fields of physics, material science, chemistry, etc and also have benefits for industries. This paper shortly reports the ray tracing calculations for the optical design of this beamline. The results show that bending magnet source would satisfy the nowadays users requirements, although insertion device should also be considered for covering the requirements of the future users. In this paper the effects of the optical elements on the users' requirements have been discussed to obtain the... 

    Diamond configuration for non-reciprocal transmission

    , Article IEEE Journal of Quantum Electronics ; Volume 53, Issue 4 , 2017 ; 00189197 (ISSN) Khorasani, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    A system scheme is presented, which allows non-reciprocal wave transmission or directional amplification of electromagnetic signals, using a boxed four-node method. Edges represent strong hopping interactions and diagonals stand for weak parametric interactions. Using careful optimization of values for design parameters, we are able to obtain non-reciprocity in excess of 12 and 130 dB for intrinsic and extrinsic configurations at identical input/output frequencies. For the directional amplification, an isolation as high as 40 dB is demonstrated with the forward/backward gains of ±20 dB. Cascading two such systems potentially can offer high isolations at high gains. © 1965-2012 IEEE  

    Resonant tunneling based filter design using legendre polynomial expansion

    , Article Photonics North 2006, Quebec City, QB, 5 June 2006 through 8 June 2006 ; Volume 6343 II , 2006 ; 0277786X (ISSN) ; 0819464287 (ISBN); 9780819464286 (ISBN) Chamanzar, M ; Mehrany, K ; Rashidian, B ; Akbari, M ; Sharif University of Technology
    In this paper optical filters based on photonic resonant tunneling effect are analyzed by using the polynomial expansion method. Amplitude and phase response together with their dependency on the physical parameters of the filters are also investigated. These steep-edge filters show low insertion loss amplitude response, and linear phase variation in their passband, a suitable feature for WDM and DWDM applications where constant time delay and dispersion free devices are needed. Two kinds of filters, namely discrete level and continuous profile filters are introduced. These structures can be analyzed and designed by using Transfer Matrix Method. However, this approach suffers from inaccuracy... 

    Operation of an opto-mechanical system using a double-cell design for liquid color recognition

    , Article Optics and Lasers in Engineering ; Volume 51, Issue 7 , July , 2013 , Pages 848-855 ; 01438166 (ISSN) Golnabi, H ; Sharif University of Technology
    Design and operation of an opto-mechanical system employing a double-cell is reported here for the color liquid reflection studies. The reported system consists of a double-fiber optical design and an electro-mechanical scanning system. In this arrangement one fiber transmits the source light to the object surface and the second one transmits the light reflected from the sample to a photodetector. By scanning the double-fiber assembly in one-direction reflection properties of different color liquids are investigated. Reflection signals depend on the cell surface structure and the cell filled material. Two sets of flat/cylindrical cells made of almost similar glass materials are used for this... 

    Using three different optical fiber designs to study humidity effect on the air refractive index

    , Article Optics and Lasers in Engineering ; Volume 50, Issue 11 , November , 2012 , Pages 1495-1500 ; 01438166 (ISSN) Golnabi, H ; Sharif University of Technology
    Design and operation of three different optical designs based on the light intensity modulation for investigation of the humidity effects on the air index of refraction are described. The measurement variable is the transmitted power, which depends on the refractive index of the medium in the path of a fiber-to-fiber optical design. Three different probes (probe #1, #2, and #3) are tested in which probe #1 and probe #2 can also check the presence of water or any other transparent liquid in the gap between the two axial fibers. Performances of the new systems are tested as a refractive index monitoring mean and experimental results are given. The variations of the modulated powers as... 

    Liquid color recognition by using an optical reflection system

    , Article Journal of Applied Sciences ; Volume 12, Issue 18 , 2012 , Pages 1917-1924 ; 18125654 (ISSN) Siadat, M ; Golnabi, H ; Sharif University of Technology
    ANSInet  2012
    Operation of an optomechanical system for color reflection study is reported. The reported system consists of a double-fiber optical design and an electro-mechanical scanning system. In the double-fiber arrangement one fiber transmits the source light to the target surface and the second one sends the reflected light off the sample target to a photodetector. By scanning the double-fiber probe in one-direction reflection properties of different color liquid samples are investigated in this study. A cubic cell made of glass material is used as the liquid container and reflection signals are compared for different filled color liquids. The maximum reflection signals are: for the yellow color... 

    Investigation of humidity effect on the air refractive index using an optical fiber design

    , Article Journal of Applied Sciences ; Volume 11, Issue 16 , 2011 , Pages 3022-3027 ; 18125654 (ISSN) Mehrabani, A ; Golnabi, H ; Sharif University of Technology
    In this study operation of an optical design based on the intensity modulation for the refractive index change has been described. The reported instrument measures the transmitted output power depending up on the medium refractive index in the light path of a fiber-to-fiber design. A liquid cell is located between the fibers in the light path and power variations for different cold and hot water levels in the cell are measured. By using a reference humidity meter the calibration curve representing the relative humidity (%RH) as a function of the transmitted output power is obtained. For the hot water with the final temperature of T = 32.7°C the output power range of 255.0 -313.OnW is... 

    Design and operation of a double-fiber scanning system for surface profiling

    , Article Optics and Lasers in Engineering ; Volume 49, Issue 8 , 2011 , Pages 1032-1039 ; 01438166 (ISSN) Golnabi, H ; Sharif University of Technology
    Design and operation of an opto-mechanical system for surface profiling are reported in this study. The reported system consists of a double-fiber optical design and an electro-mechanical scanning system. In this arrangement one fiber transmits the source light to the object surface and the second one transmits the light reflected off the surface to a photodetector. By scanning the double-fiber assembly in one-direction, reflection properties of different curved surfaces are investigated. Reflection signals for the cylindrical surfaces made with different curvatures and materials are reported. In order to see the effect of the surface material, for a fixed radius cylinder, the surface is... 

    Effects of temperature variations on the performance of a space imaging system baffle

    , Article Proceedings of SPIE - The International Society for Optical Engineering, 7 September 2015 through 10 September 2015 ; Volume 9626 , 2015 ; 0277786X (ISSN) ; 9781628418156 (ISBN) Haghshenas, J ; Mohasel Afshari, B ; Sharif University of Technology
    SPIE  2015
    All the star trackers must be composed of a baffle system to removes stray lights intensity. The baffle is designed to mount in front of the optical system. The performance of a star tracker is often limited by the stray light level on the detector. According to the space conditions, the baffle may deflect due to the temperature variation during the mission. Sun heat flux imposed to the baffle from one side and heat radiates from baffle to the space in all sides. In our case, the baffle is fixed to the satellite structure by four titanium screw. A finite element model has been used to modeling the baffle and temperature distribution and deflection is obtained in worst cold and hot... 

    NVH analysis and improvement of a vehicle body structure using DOE method

    , Article Journal of Mechanical Science and Technology ; Volume 23, Issue 11 , 2010 , Pages 2980-2989 ; 1738494X (ISSN) Azadi, S ; Azadi, M ; Zahedi, F ; Sharif University of Technology
    The improvement of a vehicle body structure under the constraint of noise, vibration and harshness (NVH) behavior is investigated by using design of experiments (DOE) method. First, car body geometry is modeled in CATIA and meshed in HYPERMESH software. Then, a modal analysis between 0-50 Hz is done by MSC NASTRAN. A frequency map of the body is extracted and compared with a reference map to identify shortcomings. By using factorial and response surface Methods (RSM), optimization of the NVH performance is accomplished. An algorithm is proposed to improve the car NVH behavior. At last, in order to verify the present algorithm, forced vibration is analyzed under real road inputs for the model... 

    Investigating the effect of design parameters on the response time of a highly sensitive microbial hydrogen sulfide biosensor based on oxygen consumption

    , Article Biosensors and Bioelectronics ; Volume 70 , 2015 , Pages 106-114 ; 09565663 (ISSN) Vosoughi, A ; Yazdian, F ; Amoabediny, G ; Hakim, M ; Sharif University of Technology
    Elsevier Ltd  2015
    A novel hydrogen sulfide microbial biosensor was developed based on investigating the influence of four design parameters: cell concentration, immobilization bed type, hydrogen sulfide concentration, and geometrical shape of the biosensor. Thiobacillus thioparus was used as the recognition element and it was immobilized on sodium alginate as well as agarose bed. The results were optimized by the application of statistical optimization software based on response time of the system. Oxygen reduction was considered as the detection sign. Sodium alginate solution with a concentration of 2.3% (w/v) and optical density of 10 at 605. nm was found as the optimum conditions for immobilization with... 

    Surface profiling using a double-fiber optical design

    , Article Optics and Lasers in Engineering ; Volume 48, Issue 4 , April , 2010 , Pages 421-426 ; 01438166 (ISSN) Golnabi, H ; Sharif University of Technology
    In this study surface profiling is performed by using a scanning system and an opto-pair fiber design. In this method one fiber transmits the laser light to the target and the second one transmits back the light reflected off the target to a photodetector. The monitoring of the reflected light signal from a surface is accomplished by converting the photon light into an electric signal and measuring by a digital multimeter. By scanning an object mounted on a XYZ-translational stage the reflection signal profiles are obtained for plane and curved surfaces. Output reflection signal variations in the X-, Y-, and Z-directions are measured for different plane and cylindrical surfaces and compared.... 

    Geometry control of the deposited layer in a nonplanar laser cladding process using a variable structure controller

    , Article Journal of Manufacturing Science and Engineering, Transactions of the ASME ; Volume 130, Issue 3 , 2008 , Pages 0310031-03100311 ; 10871357 (ISSN) Fathi, A ; Khajepour, A ; Durali, M ; Toyserkani, E ; Sharif University of Technology
    This paper presents a closed-loop laser cladding process used in nonplanar deposition of desired metallic materials. In the proposed system, the deposited layer geometry is continuously controlled via a sliding mode controller (SMC). The controller, which uses the scanning speed as the control input, is designed based on a parametric Hammerstein model. The model is a parametric dynamic model with several unknown parameters, which are identified experimentally using the recursive least squares method. The designed SMC is robust to all model parameters' uncertainties and disturbances. The results showed that the tracking accuracy improves and the chattering effect reduces if an integrator on... 

    Mechanical induced reaction in Al-CuO system for in-situ fabrication of Al based nanocomposites

    , Article Journal of Alloys and Compounds ; Volume 465, Issue 1-2 , 2008 , Pages 151-156 ; 09258388 (ISSN) Arami, H ; Simchi, A ; Seyed Reihani, S. M ; Sharif University of Technology
    Gradual chemical (displacement) reaction between CuO and Al powders during high-energy attrition milling under a high purity argon atmosphere was studied. Differential thermal analysis (DTA), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques were employed to study the solid-state reaction. It was shown that the solid-state reaction occurred during mechanical alloying (MA) and resulted in the dissolution of copper into the aluminum lattice and formation of nanometric alumina particles. The reinforcement particles were mostly distributed at the grain boundaries of Al matrix with an average crystallite size of about 50 nm. In DTA curve of the milled powders, a small... 

    Optimal design and characterization of superparamagnetic iron oxide nanoparticles coated with polyvinyl alcohol for targeted delivery and imaging

    , Article Journal of Physical Chemistry B ; Volume 112, Issue 46 , 2008 , Pages 14470-14481 ; 15206106 (ISSN) Mahmoudi, M ; Simchi, A ; Imani, M ; Milani, A. S ; Stroeve, P ; Sharif University of Technology
    American Chemical Society  2008
    Superparamagnetic iron oxide nanoparticles (SPION) with narrow size distribution and stabilized by polyvinyl alcohol (PVA) were synthesized. The particles were prepared by a coprecipitation technique using ferric and ferrous salts with a molar Fe3+/Fe2+ ratio of 2. Using a design of experiments (DOE) approach, the effect of different synthesis parameters (stirring rate and base molarity) on the structure, morphology, saturation magnetization, purity, size, and size distribution of the synthesized magnetite nanoparticles was studied by various analysis techniques including X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) with differential scanning calorimetry (DSC)...