Publications with Fulltext

Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6

Browse

Filters

2004 - 200932010 - 20174

Advanced Search

Filter by

Settings

Department: search.filters.department.Department of PhysicsQuartile: search.filters.quartile.Q4

Search Results

Now showing 1 - 7 of 7
  • Thumbnail Image
    PublicationOpen Access
    Collective excitations of a laser driven atomic condensate in an optical cavity
    (Maik Nauka/Interperiodica Publishing, 2013) Öztop, B.; Türeci, H. E.; Department of Physics; Müstecaplıoğlu, Özgür Esat; Faculty Member; Department of Physics; College of Sciences; 1674
    We theoretically examine collective excitations of an optically driven atomic Bose-Einstein condensate, coupled to a high-finesse optical cavity. This open system has been recently used for the experimental demonstration of the Dicke superradiance of cavity photons, which is simultaneously and mutually triggered by spontaneous breaking of translational symmetry of the condensate into a crystalline order. We first develop a Hartree-Fock mean field dynamical model of the physical system. Using this model, we compute the dynamics of the cavity photons, the condensate density profile and the Dicke phase transition diagram. Both the imaginary-time and real-time evolution methods are used in the calculations. Collective excitations are determined by the solving Bogoliubov-de Gennes equations. The spectrum, softening of the modes and energetic hierarchy of excitations are determined.
  • Thumbnail Image
    PublicationOpen Access
    Morphology-dependent resonances of optical microsphere resonators for the realization of passive wavelength-division multiplexing components
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2004) Department of Physics; Department of Electrical and Electronics Engineering; İşçi, Şenol; Bilici, Temel; Serpengüzel, Ali; Kurt, Adnan; Faculty Member; Teaching Faculty; Department of Physics; Department of Electrical and Electronics Engineering; College of Sciences; N/A; N/A; 27855; 194455
    Morphology-dependent resonances of microspheres can provide the necessary optical feedback for applications in spectroscopy, laser science, and optical communications. The elastic scattering of focused light from dielectric microspheres is understood by the localization principle and the generalized Lorenz-Mie theory. We excited the morphology-dependent resonances of glass microspheres by a tunable distributed-feedback laser and detected the elastically scattered signal. Efficient coupling to morphology-dependent resonances is achieved using an optical fiber half coupler. Resonance peaks in the elastic scattering spectra and associated dips in the transmission spectra are observed experimentally. Simulation results of elastic scattering spectra of glass microspheres in the C-band are presented. (C) 2004 Society of Photo-Optical Instrumentation Engineers.
  • Thumbnail Image
    PublicationOpen Access
    Whispering-gallery modes observed in elastic scattering from submerged high-refractive-index silica microspheres
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2017) Tamer, M. S.; Gurlu, O.; Department of Physics; Yılmaz, Hasan; Yılmaz, Huzeyfe; Murib, Mohammed Sharif; Serpengüzel, Ali; Master Student; Master Student; Faculty Member; Department of Physics; College of Sciences; N/A; N/A; N/A; 27855
    The effect of the discrete values of the refractive index of the surrounding medium on the spectral behavior of the whispering-gallery modes (WGMs) in the elastic scattering spectra of high-refractive-index silica microspheres submerged in fluids, such as air, water, and glycerol, is studied. The elastic scattering spectral measurements, as well as the spectral autocorrelation analysis of these elastic scattering spectra show that the spectral-mode spacing, the spectral-mode density, and the spectral-mode definition of the WGMs decrease as the refractive index of the surrounding fluid increases. We believe that this work opens up the way for optofluidic applications of high-refractive-index silica microsphere-based guided wave optics.
  • Thumbnail Image
    PublicationOpen Access
    Analysis and optimization of diode end-pumped solid-state lasers: applicationto Nd3+ : YVO4 lasers at 1064 and 1342 nm
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2005) Buhours, S.; Department of Physics; Department of Electrical and Electronics Engineering; Sennaroğlu, Alphan; Kurt, Adnan; Faculty Member; Teaching Faculty; Department of Physics; Department of Electrical and Electronics Engineering; College of Sciences; 23851; 194455
    We describe a systematic procedure that uses experimental and numerical methods to analyze the continuous-wave power performance of diode end-pumped solid-state lasers. For the general case, saturation, excited-state absorption, and thermal lensing effects are considered and integral equations are derived to study the evolution of the pump and laser beams in the gain medium. As an application of the method, we consider two different diode end-pumped Nd3+:YVO4 lasers operating at 1064 and 1342 nm. Experimental efficiency data were first analyzed to determine the stimulated emission cross sections and the resonator losses. The best-fit laser parameters were then used to calculate the optimum crystal length that maximizes the output power of the laser. The described method should prove useful in the design of a wide range of efficient diode-pumped solid-state lasers.
  • Thumbnail Image
    PublicationOpen Access
    Decoupling of multifrequency dipole antenna arrays for microwave imaging applications
    (Hindawi, 2010) Saenz, E.; Özbay, E.; Ederra, I.; Gonzalo, R.; Department of Physics; Güven, Kaan; Faculty Member; Department of Physics; College of Sciences; 52290
    The mutual coupling between elements of a multifrequency dipole antenna array is experimentally investigated by S-parameter measurements and planar near-field scanning of the radiated field. A multifrequency array with six dipoles is analyzed. In order to reduce the coupling between dipoles, a planar metasurface is placed atop the array acting as superstrate. The mutual coupling of the antenna elements in the absence and presence of the superstrate is presented comparatively. Between 3 and 20 dB mutual coupling reduction is achieved when the superstrate is used. By scanning the field radiated by the antennas and far-field measurements of the radiation pattern, it is observed that the superstrate confines the radiated power, increases the boresight radiation, and reduces the endfire radiation.
  • Thumbnail Image
    PublicationOpen Access
    Bistable behavior of a two-mode Bose-Einstein condensate in an optical cavity
    (Maik Nauka/Interperiodica Publishing, 2013) Safaei, S.; Tanatar, B.; Department of Physics; Müstecaplıoğlu, Özgür Esat; Faculty Member; Department of Physics; College of Sciences; 1674
    We consider a two-component Bose-Einstein condensate in a one-dimensional optical cavity. Specifically, the condensate atoms are taken to be in two degenerate modes due to their internal hyperfine spin degrees of freedom and they are coupled to the cavity field and an external transverse laser field in a Raman scheme. A parallel laser also excites the cavity mode. When the pump laser is far detuned from its resonance atomic transition frequency, an effective nonlinear optical model of the cavity-condensate system is developed under the discrete mode approximation (DMA), while matter-field coupling has been considered beyond the rotating wave approximation. By analytical and numerical solutions of the nonlinear dynamical equations, we examine the mean cavity field and population difference (magnetization) of the condensate modes. The stationary solutions of both the mean cavity field and normalized magnetization demonstrate bistable behavior under certain conditions for the laser pump intensity and matter-field coupling strength.
  • Thumbnail Image
    PublicationOpen Access
    Repetition rate control in continuous-wave-pumped, passively Q-switched solid-state lasers
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2007) Department of Physics; Department of Electrical and Electronics Engineering; Sennaroğlu, Alphan; Çankaya, Hüseyin; Kurt, Adnan; Faculty Member; Researcher; Teaching Faculty; Department of Physics; Department of Electrical and Electronics Engineering; College of Sciences; 23851; N/A; 194455
    We describe a technique for the adjustment and control of repetition rates in continuous-wave-pumped, passively Q-switched solid-state lasers. The method uses a movable intracavity lens to modify the mode matching and hence the gain of the laser beam per pass. The technique was applied to a diode-pumped Nd3+: YVO4 laser passively Q-switched with a Cr4+: YAG saturable absorber at 1064 nm. At a fixed pump power of 5.4 W, we were able to continuously adjust the repetition rate between 13.8 and 25 kHz by translating an intracavity converging lens. We also demonstrate that by adjusting the lens position, the repetition rate can be kept at a desired value as the pump power varies. In particular, as the pump power was increased from 3.95 to 5.9 W, the lens position was varied by 0.91 cm to keep the repetition rate constant at 13.8 kHz. Rate-equation formalism was used to investigate the variation of the repetition rate as a function of lens position, and very good agreement was obtained between experiment and theory. (c) 2007 Society of Photo-Optical Instrumentation Engineers.