Advances in Optics http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Delocalized Photomechanical Effects of UV ns Laser Ablation on Polymer Substrates Captured by Optical Holography Workstation: An Overview on Experimental Result Wed, 15 Oct 2014 00:00:00 +0000 http://www.hindawi.com/journals/ao/2014/105482/ A brief overview of results from an experimental investigation performed on polymer materials to examine delocalized photomechanical effects generated due to UV laser ablation is provided. Delocalized structural modifications were observed in PMMA, PS by means of optical holographic interferometry. The integrity of samples was examined before and after irradiation in 193 and 248 nm (15 ns) above and below ablation threshold, F = 0.1–1.0 J/cm2. A value of structural continuity was initially determined for each sample by generation of a reference holographic image before irradiation. Microscopic discontinuities were intentionally induced to act as preexistent defects. Sequential holographic recording monitored the growth of morphological alterations according to the number of pulses in the neighbor as well as far from the preexistent discontinuities. The imposed alterations are visually observable at the whole extent of the irradiated sample in distances far off the ablation spot as local cracks and voids. The induced flaws cannot be classified as transient or instantly generated. Fracture follows a long-term emergence and deterioration pattern. Extensively fluctuated long-term effects were also observed in laser-assisted varnish removal of multilayered technical samples simulating Byzantine icons with decrease of effect duration and fluctuation being according to increase in sample homogeneity. Vivi Tornari Copyright © 2014 Vivi Tornari. All rights reserved. Rare Earth Doped Silica Optical Fibre Sensors for Dosimetry in Medical and Technical Applications Tue, 14 Oct 2014 12:53:40 +0000 http://www.hindawi.com/journals/ao/2014/974584/ Radioluminescence optical fibre sensors are gaining importance since these devices are promising in several applications like high energy physics, particle tracking, real-time monitoring of radiation beams, and radioactive waste. Silica optical fibres play an important role thanks to their high radiation hardness. Moreover, rare earths may be incorporated to optimise the scintillation properties (emission spectrum, decay time) according to the particular application. This makes doped silica optical fibres a very versatile tool for the detection of ionizing radiation in many contexts. Among the fields of application of optical fibre sensors, radiation therapy represents a driving force for the research and development of new devices. In this review the recent progresses in the development of rare earth doped silica fibres for dosimetry in the medical field are described. After a general description of advantages and challenges for the use of optical fibre based dosimeter during radiation therapy treatment and diagnostic irradiations, the features of the incorporation of rare earths in the silica matrix in order to prepare radioluminescent optical fibre sensors are presented and discussed. In the last part of this paper, recent results obtained by using cerium, europium, and ytterbium doped silica optical fibres in radiation therapy applications are reviewed. N. Chiodini, A. Vedda, and I. Veronese Copyright © 2014 N. Chiodini et al. All rights reserved. A Theoretical Study of Bulk Tungsten (W) Based on Momentum Transfer (-Dependent) Wed, 08 Oct 2014 12:39:26 +0000 http://www.hindawi.com/journals/ao/2014/814909/ The ground state electronic properties of bulk (W) were studied within the density functional theory (DFT). We have also analyzed the momentum- (q-) dependent loss function, dielectric constant, and optical conductivity (OC) within TD-DFT random-phase approximation (RPA). The loss function is plotted in the energy range 0–55 eV. The energy loss function spectrum shows four prominent peaks, two lower peaks below along with two sharp peaks above 30 eV. The different nature of peaks depends on the momentum transfer q. The peak caused by interband transition showed a less pronounced dispersion. From the dielectric function curve we have predicted the plasmon excitation at around 1.75 eV and calculated the corresponding plasma frequency  s−1. D. P. Rai and R. K. Thapa Copyright © 2014 D. P. Rai and R. K. Thapa. All rights reserved. From Single Atoms to Engineered “Super-Atoms”: Interfacing Photons and Atoms in Free Space Wed, 08 Oct 2014 11:14:24 +0000 http://www.hindawi.com/journals/ao/2014/572084/ During the last decades the development of laser cooling and trapping has revolutionized the field of quantum optics. Now we master techniques to control the quantum properties of atoms and light, even at a single atom and single photon level. Understanding and controlling interactions of atoms and light both on the microscopic single particle and on the macroscopic collective levels, are two of the very active directions of the current research in this field. The goal is to engineer quantum systems with tailored properties designed for specific applications. One of the ambitious applications on this way is interfacing quantum information for quantum communication and quantum computing. We summarize here theoretical ideas and experimental methods for interfacing atom-based quantum memories with single flying photons. Yevhen Miroshnychenko Copyright © 2014 Yevhen Miroshnychenko. All rights reserved. Preparation and Optical Investigations of [()TiO3]-[2SiO2B2O3]-[CeO2] Glasses Tue, 30 Sep 2014 13:06:21 +0000 http://www.hindawi.com/journals/ao/2014/687207/ We are reporting synthesis and structural and optical investigation of strontium bismuth titanate borosilicate glasses with addition of one mole percent cerium oxide (CeO2). Glasses were synthesized by conventional rapid melt quench method. XRD studies of the glass samples confirm the amorphous nature. Infrared absorption spectra various strontium bismuth titanate borosilicate glass samples having glass system 60[()TiO3]-39[2SiO2B2O3]-1[CeO2] () were recorded over a continuous spectral range from 400 to 4000 cm−1. IR spectra were analyzed to determine and differentiate of various vibrational modes in the structural change. Raman spectroscopy of all glass samples was also carried out in the wave number range from 200 to 2000 cm−1. Chandkiram Gautam, Anod Kumar Singh, and Abhishek Madheshiya Copyright © 2014 Chandkiram Gautam et al. All rights reserved. Self-Focusing of Hermite-Cosh-Gaussian Laser Beams in Plasma under Density Transition Mon, 29 Sep 2014 10:16:41 +0000 http://www.hindawi.com/journals/ao/2014/942750/ Self-focusing of Hermite-Cosh-Gaussian (HChG) laser beam in plasma under density transition has been discussed here. The field distribution in the medium is expressed in terms of beam-width parameters and decentered parameter. The differential equations for the beam-width parameters are established by a parabolic wave equation approach under paraxial approximation. To overcome the defocusing, localized upward plasma density ramp is considered, so that the laser beam is focused on a small spot size. Plasma density ramp plays an important role in reducing the defocusing effect and maintaining the focal spot size up to several Rayleigh lengths. To discuss the nature of self-focusing, the behaviour of beam-width parameters with dimensionless distance of propagation for various values of decentered parameters is examined by numerical estimates. The results are presented graphically and the effect of plasma density ramp and decentered parameter on self-focusing of the beams has been discussed. Manzoor Ahmad Wani and Niti Kant Copyright © 2014 Manzoor Ahmad Wani and Niti Kant. All rights reserved. Self-Similarity in Transverse Intensity Distributions in the Farfield Diffraction Pattern of Radial Walsh Filters Wed, 17 Sep 2014 09:24:57 +0000 http://www.hindawi.com/journals/ao/2014/352316/ In a recent communication we reported the self-similarity in radial Walsh filters. The set of radial Walsh filters have been classified into distinct self-similar groups, where members of each group possess self-similar structures or phase sequences. It has been observed that, the axial intensity distributions in the farfield diffraction pattern of these self-similar radial Walsh filters are also self-similar. In this paper we report the self-similarity in the intensity distributions on a transverse plane in the farfield diffraction patterns of the self-similar radial Walsh filters. P. Mukherjee and L. N. Hazra Copyright © 2014 P. Mukherjee and L. N. Hazra. All rights reserved. Reduction in Edge-Ringing in Aberrated Images of Coherent Edge Objects by Multishaded Aperture Wed, 20 Aug 2014 00:00:00 +0000 http://www.hindawi.com/journals/ao/2014/963980/ The images of a straight edge in coherent illumination produced by an optical system with circular aperture and apodized with multiple filters have been studied. The most common problem encountered in the coherent-imaging techniques is the edge-ringing. To minimize the edge-ringing, multishaded aperture method has been proposed. Image intensity distribution curves are drawn and edge-ringing values are evaluated. The results are compared to that of the airy case with the use of single, double and triple filtering. Venkanna Mekala and Karuna Sagar Dasari Copyright © 2014 Venkanna Mekala and Karuna Sagar Dasari. All rights reserved. The Spectral Analysis of Dynamic Laser Speckle Patterns Generated by Brownian Particle Suspensions: A Stroboscopic Effect Based Filtering Technique Tue, 05 Aug 2014 06:07:38 +0000 http://www.hindawi.com/journals/ao/2014/813602/ The power spectrum of the time-varying intensity in the dynamic laser speckle patterns is determined by passing the shifted power spectrum through a low-pass filter which is implemented via the signal integration. The light intensity is modulated sinusoidally to induce the stroboscopic effect which shifts the resonant frequency component of the spectrum to 0 Hz. The homodyne dynamic laser speckles generated by the quasi-inelastic scattering of the Brownian motions in colloidal suspensions are investigated. Within the frequency range from 10 Hz to 10 kHz used in this work, the bandwidth of the Lorenztian power spectrums is shown to be inversely proportional to the particle size, which is in agreement with the prediction of the dynamic light scattering theory of diffusing particle. The spatial variation observed in the full-field power spectrum maps is caused by the nonuniform distribution of average speckle intensity and varies with the modulation frequency. However, the bandwidths measured at different locations are found to be intensity independent. Dake Wang, James Ranger, and Adam Moyer Copyright © 2014 Dake Wang et al. All rights reserved. Effects of Li+ Codoping on the Optical Properties of SrAl2O4 Long Afterglow Ceramic Phosphors Mon, 04 Aug 2014 08:38:16 +0000 http://www.hindawi.com/journals/ao/2014/459065/ Rare-earths codoped long afterglow strontium aluminate phosphors with high brightness were synthesized via a facile combustion synthesis method using urea as a fuel. The resulted phosphor particles were analyzed by using X-ray diffraction and field emission scanning electron microscope, whereas their optical properties were monitored by photoluminescence spectroscopy. The prepared SrAl2O4:Eu2+, Dy3+, Li+ samples showed a broad green-yellowish emission, peaking at 512 nm when excited by 348 nm. Compared to traditional SrAl2O4:Eu2+, Dy3+ phosphor, the initial luminescence brightness of SrAl2O4:Eu2+, Dy3+, codoped with Li+ improved from 1.89 cd/m2 to 2.71 cd/m2 and the afterglow decay time was prolonged from 103 to 121 min. The possible mechanism of SrAl2O4:Eu2+, Dy3+, Li+ phosphorescence enhancement has been discussed. Timur Sh. Atabaev, Hong Ha Thi Vu, Mac Kim, Yong Suk Yang, Hyung-Kook Kim, and Yoon-Hwae Hwang Copyright © 2014 Timur Sh. Atabaev et al. All rights reserved. Analyzing Density Operator in Thermal State for Complicated Time-Dependent Optical Systems Thu, 24 Jul 2014 14:05:03 +0000 http://www.hindawi.com/journals/ao/2014/141076/ Density operator of oscillatory optical systems with time-dependent parameters is analyzed. In this case, a system is described by a time-dependent Hamiltonian. Invariant operator theory is introduced in order to describe time-varying behavior of the system. Due to the time dependence of parameters, the frequency of oscillation, so-called a modified frequency of the system, is somewhat different from the natural frequency. In general, density operator of a time-dependent optical system is represented in terms of the modified frequency. We showed how to determine density operator of complicated time-dependent optical systems in thermal state. Usually, density operator description of quantum states is more general than the one described in terms of the state vector. Jeong Ryeol Choi, Ji Nny Song, and Yeontaek Choi Copyright © 2014 Jeong Ryeol Choi et al. All rights reserved. Submicron Surface Vibration Profiling Using Doppler Self-Mixing Techniques Wed, 23 Jul 2014 00:00:00 +0000 http://www.hindawi.com/journals/ao/2014/576380/ Doppler self-mixing laser probing techniques are often used for vibration measurement with very high accuracy. A novel optoelectronic probe solution is proposed, based on off-the-shelf components, with a direct reflection optical scheme for contactless characterization of the target’s movement. This probe was tested with two test bench apparatus that enhance its precision performance, with a linear actuator at low frequency (35 µm, 5–60 Hz), and its dynamics, with disc shaped transducers for small amplitude and high frequency (0.6 µm, 100–2500 Hz). The results, obtained from well-established signal processing methods for self-mixing Doppler signals, allowed the evaluation of vibration velocity and amplitudes with an average error of less than 10%. The impedance spectrum of piezoelectric (PZ) disc target revealed a maximum of impedance (around 1 kHz) for minimal Doppler shift. A bidimensional scan over the PZ disc surface allowed the categorization of the vibration mode (0, 1) and explained its deflection directions. The feasibility of a laser vibrometer based on self-mixing principles and supported by tailored electronics able to accurately measure submicron displacements was, thus, successfully demonstrated. Tânia Pereira, Mariana Sequeira, Pedro Vaz, Ana Tomé, Helena C. Pereira, Carlos Correia, and João Cardoso Copyright © 2014 Tânia Pereira et al. All rights reserved. Field Squeezing in a Quantum-Dot Molecule Jaynes-Cummings Model Thu, 03 Jul 2014 07:54:24 +0000 http://www.hindawi.com/journals/ao/2014/395836/ We investigate the field squeezing in a system composed of an initial coherent field interacting with two quantum dots coupled by electron tunneling. An approximate quantum-dot molecule Jaynes-Cummings model describing the system is given, and the effects of physical quantities, such as the temperature, phonon-electron interaction, mean photon number, field detuning, and tunneling-level detuning, are discussed in detail. Xu Chu, Xiaodong Ma, Ying Wang, Qingchun Zhou, and Yu Zhou Copyright © 2014 Xu Chu et al. All rights reserved. Hybrid Materials for Integrated Photonics Thu, 26 Jun 2014 10:53:35 +0000 http://www.hindawi.com/journals/ao/2014/891395/ In this review materials and technologies of the hybrid approach to integrated photonics (IP) are addressed. IP is nowadays a mature technology and is the most promising candidate to overcome the main limitations that electronics is facing due to the extreme level of integration it has achieved. IP will be based on silicon photonics in order to exploit the CMOS compatibility and the large infrastructures already available for the fabrication of devices. But silicon has severe limits especially concerning the development of active photonics: its low efficiency in photons emission and the limited capability to be used as modulator require finding suitable materials able to fulfill these fundamental tasks. Furthermore there is the need to define standardized processes to render these materials compatible with the CMOS process and to fully exploit their capabilities. This review describes the most promising materials and technological approaches that are either currently implemented or may be used in the coming future to develop next generations of hybrid IP devices. Paolo Bettotti Copyright © 2014 Paolo Bettotti. All rights reserved. Fiber-Wireless (FiWi) Broadband Access Networks in an Age of Convergence: Past, Present, and Future Sun, 22 Jun 2014 10:41:18 +0000 http://www.hindawi.com/journals/ao/2014/945364/ After describing the beginnings and state of the art of integrated fiber-wireless (FiWi) broadband access networks in great detail, we briefly review recent progress and point to various ongoing research activities, including the design of energy-efficient “green” FiWi access networks, advanced survivability techniques, and integration of wireless and fiber optic sensors, towards realizing adaptable, dependable, and ecoconscious future-proof broadband access networks based on both wireless and shared passive fiber media. Furthermore, we discuss service, application, business, and operation related aspects, which motivate access technology to move into a substantially different direction in the long run than continued capacity provisioning. Given that most 4G cellular mobile network researches so far have been focusing on the achievable performance gains in the wireless front-end only without looking into the details of backhaul implementations and possible backhaul bottlenecks, we identify open key research challenges for FiWi broadband access networks. We explore ways of how they can be deployed across relevant economic sectors other than telecommunications per se, taking major paradigm shifts such as the Third Industrial Revolution, Energy Internet, smart grid, and explosion of mobile data traffic in today’s cellular networks into account. Martin Maier Copyright © 2014 Martin Maier. All rights reserved.