Researcher:
Zakwan, Muhammad

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PhD Student

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Muhammad

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Zakwan

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Zakwan, Muhammad

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Now showing 1 - 8 of 8
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    Publication
    Mid-infrared elastic scattering from germanium microspheres
    (IEEE, 2016) N/A; N/A; N/A; N/A; Department of Physics; Department of Physics; Zakwan, Muhammad; Bayer, Mustafa Mert; Anwar, Muhammad Sohail; Gökay, Ulaş Sabahattin; Serpengüzel, Ali; PhD Student; Master Student; Master Student; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; N/A; 27855
    Because of their ultrahigh optical nonlinearities and extremely broad transparency window, germanium microsphere resonators offer the potential for optical processing devices, especially in the mid-infrared (mid-IR) wavelengths. As a semiconductor material for microphotonics applications [1], germanium is particularly attractive owing to its large nonlinearity, high optical damage threshold compared with traditional nonlinear glass materials, and above all, its broad transparency window, extending from the near-IR into the mid-IR. Germanium based optical components have found numerous applications in imaging systems operating in the mid-IR wavelengths, where the principal natural greenhouse gases do not exhibit strong absorption. These applications include rapid sensing and diagnosis [2,] [3], industrial process controls, environmental monitors to hazardous chemical detection [4]. Germanium also is a good electromagnetic shielding material, an attribute that has become increasingly important for modern military applications, where other signals (within the millimeter and centimeter wavelength range) can be strong enough to interfere with nearby IR systems. Elastic light scattering from a germanium microsphere has already been observed in the near-IR [5]. Here, elastic light scattering from a germanium microsphere in the mid-IR region is numerically analyzed using generalized Lorenz-Mie theory (GLMT) [6]. Light interaction with microspheres of various materials is of much interest because of their photonic properties [7]. Germanium has a refractive index of 4, which is even higher than the refractive index of silicon (3.5) in the mid-IR region. The higher refractive index results in higher quality factor morphology dependent resonances (MDRs). A higher value of Q indicates a longer lifetime of the photons trapped inside the cavity and a narrower MDR. Here, the MDRs are observed numerically in the transverse magnetically (TM) and transverse electrically (TE) polarized 90° elastic scattering and 0° transmission for a 40 µm radius germanium microsphere in the mid-IR wavelengths ranging from 5.4 µm to 5.6 µm [8]. The mode spacing of approximately 41 nm between the resonances with the same radial mode order and consecutive polar mode number shows good correlation with the optical size of the germanium microsphere. The germanium microsphere with its high quality factor MDRs can be suitable for optical monitoring and sensing applications in the mid-IR, which require a high spectral resolution [9].
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    Symmetric meandering distributed feedback structures for silicon photonic circuits
    (Ieee-Inst Electrical Electronics Engineers Inc, 2020) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Physics; Department of Electrical and Electronics Engineering; Department of Physics; Chaudhry, Muhammad Rehan; Zakwan, Muhammad; Onbaşlı, Mehmet Cengiz; Serpengüzel, Ali; PhD Student; PhD Student; Faculty Member; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; N/A; N/A; 258783; 27855
    Fano lineshapes and electro-magnetically induced transparency-like peaks in the transmittance of a transverse electric polarization silicon-on-insulator symmetric meandering distributed feedback photonic structure are demonstrated. The coupling constants at the five identical directional couplers are varied to obtain the desired spectral responses. The numerically simulated and experimentally measured transmittance spectra are in good agreement with each other. The numerically calculated and experimentally measured insertion loss for the symmetric meandering distributed feedback structure with directional coupler coupling length L-c = 10 mu m are respectively -5 dB and -17 dB, including the grating couplers. Fano lineshapes with mode splitting is observed at directional coupler coupling constant value C of 0.24. For coupling constant value of C similar to 0.78, electro-magnetically induced transparency-like peaks are observed, and spectrally adjusted by varying the directional coupler coupling length. Fano lineshapes show an extinction ratio of more than 26 dB and slope ratio of 368 dB/nm. Electro-magnetically induced transparency-like peaks show a quality-factor on the order of 5 x 10(4). The symmetric meandering distributed feedback structure shows promise for possible applications as an optical switch, and an optical filter in wavelength division multiplexing and data networks, as well as optical sensors in optical diagnostics, using silicon photonics.
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    Publication
    Optical fiber excitation of fano resonances in a silicon microsphere
    (Taylor & Francis Inc, 2016) Demir, Abdullah; N/A; N/A; Department of Physics; Department of Physics; Gökay, Ulaş Sabahattin; Zakwan, Muhammad; Serpengüzel, Ali; PhD Student; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; 27855
    In this article, Fano lineshape whispering gallery modes were observed in the light scattering spectrum of a silicon microsphere in near-infrared telecommunication wavelengths. A simple model is presented to explain the transition from Lorentzian lineshape to the Fano lineshape resonances with the coupled-mode theory of multiple whispering gallery modes. Polar mode spacing of 0.23 nm is observed in the spectra, which correlates well with the calculated value. The quality factor of the Lorentzian and Fano resonances are on the order of 10(5). By using an appropriate interface design for the microsphere coupling geometries, Fano lineshape optical resonances herald novel device applications for silicon volumetric lightwave circuits.
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    Spherical silicon optical resonators: possible applications to biosensing
    (Springer Heidelberg, 2014) N/A; N/A; Department of Physics; Department of Physics; Gökay, Ulaş Sabahattin; Zakwan, Muhammad; Serpengüzel, Ali; PhD Student; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; 27855
    We observed whispering gallery modes in the 90 degrees elastic light scattering and 0 degrees transmission spectra of a 500 mu m silicon microsphere in the near-infrared telecommunication wavelengths. The whispering gallery modes have quality factors on the order of 10(5). An autocorrelation function analysis of the 90 degrees elastic light scattering and 0 degrees transmission spectra is performed. The differential autocorrelation of the 90 degrees elastic light scattering and 0 degrees transmission spectra reveal a spectral mode spacing 0.23nm of the whispering gallery modes, which can be used for spectral calibration as well as the calibration of the microsphere size. The spectral shift of the whispering gallery modes can be measured for biosensing applications. An estimation analysis is performed for the adsorption of 30 DNA base pairs on the microsphere results in a wavelength shift of 0.57 nm, which is approximately 40 times the linewidth of the whispering gallery modes. This high sensitivity heralds silicon microspheres as possible candidates for biosensing applications.
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    Publication
    Optoelectronic applications of sapphire microspheres
    (Electromagnetics Academy, 2015) N/A; N/A; N/A; N/A; Department of Physics; Department of Physics; Zakwan, Muhammad; Anwar, Muhammad Sohail; Bukhari, Syed Sultan Shah; Gökay, Ulaş Sabahattin; Serpengüzel, Ali; PhD Student; Master Student; PhD Student; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; N/A; 27855
    The sphere with its highly symmetric geometrical shape enhances the efficiency of optical effects with its high quality factor morphology dependent resonances (MDRs). We report here on numerical studies of elastic light scattering in a sapphire microdisk coupled to slab waveguides, i.e., the 2D analog of a microsphere coupled to the 2D analog of an optical waveguide. The numerical electromagnetic simulations for the surface electric field strength are performed at 800 nm. The experimental elastic light scattering measurements are also proposed in the near-infrared from sapphire microspheres. 800 nm operation with sapphire microspheres is suitable for local area networks (LANs) applications such as channel dropping, filtering, switching, modulation, and monitoring.
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    Spatial intensity profiling of elastic and inelastic scattering in isotropic and anisotropic liquids by immersion of a spherical silicon photocell
    (Optical Soc Amer, 2017) Taira, Kenichi; Omura, Etsuji; Nakata, Josuke; N/A; N/A; N/A; N/A; N/A; Department of Physics; Department of Physics; Humayun, Muhammad Hamza; Bukhari, Syed Sultan Shah; Zakwan, Muhammad; Bayer, Mustafa Mert; Gökay, Ulaş Sabahattin; Serpengüzel, Ali; Master Student; PhD Student; PhD Student; Master Student; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; N/A; N/A; 27855
    The transverse spatial intensity distribution of elastic and inelastic light scattering in passive and active as well as weak and strong scattering liquid media has been studied by using Sphelar One p-n junction silicon spherical photocells. We immersed a Sphelar One in these scattering solutions and measured the photoconductive response in reverse biased photodiode (PD) configuration. The passive weak scattering medium was pure ethanol (EtOH), whereas the passive strong scattering medium was 5CB nematic liquid crystal (NLC). Solutions of 0.1 mM Rhodamine 640 perchlorate laser dye in EtOH and in 5CB NLC were used as active scattering media. The response of Sphelar One was strongly enhanced in 5CB NLC compared to EtOH, as well as in active solutions compared to passive solutions. The morphology of the Sphelar One is already advantageous over conventional one-sided planar PDs inside liquid solutions. This omnidirectional response of the Sphelar One can further be enhanced by optimizing the properties of the surrounding passive elastic and active inelastic scatterers.
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    Spectroscopy of a Nd:YVO4 diode pumped solid state laser
    (Wiley, 2017) N/A; Department of Physics; N/A; N/A; N/A; Department of Physics; Department of Physics; Öztürk, Oğuzhan Mete; Bayer, Mustafa Mert; Anwar, Muhammad Sohail; Zakwan, Muhammad; Serpengüzel, Ali; Undergraduate Student; Master Student; Master Student; PhD Student; Faculty Member; College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; N/A; 27855
    The 1064 nm lasing, and 1074 nm, and 1084 nm luminescence are observed in a Nd:YVO4 DPSSL along with their corresponding SHG. Fundamental transitions are analyzed in terms of Stark effect. The relative intensity of the 1064 nm laser line is an order of magnitude bigger than the luminescence lines.
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    PublicationOpen Access
    Silica glass-based fiber optic distributed meandering waveguides for integrated photonics
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2018) Dağ, Ceren B.; Department of Physics; Department of Physics; Serpengüzel, Ali; Zakwan, Muhammad; Faculty Member; PhD Student; Graduate School of Sciences and Engineering; 27855; N/A
    Distributed meandering waveguide based fiber optic components are introduced, categorized, and numerically analyzed in the near-infrared. The building block of all meandering waveguide components is the meandering loop mirror. The other components are the meandering resonator, meandering distributed feedback structure, symmetric and antisymmetric meandering resonator, symmetric and antisymmetric meandering distributed feedback structures giving rise to transmission spectra with Lorentzian, Rabi, Fano, coupled resonator induced transparency, and winged Lorentzian lineshapes. With this variety of spectral responses, distributed meandering waveguide fiber optic components are suitable as filters, and delay line elements in fiber optic communication, and as sensor elements in fiber optic diagnostics.