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APPLICATIONS-CENTERED RESEARCH IN OPTICS

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Early Posting

Accepted papers to appear in an upcoming issue

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Articles 1 to 20 of 122 Next Page >>

September


(LITH2014) Transport of Intensity phase imaging in the presence of curl effects induced by strongly absorbing photomasks

  • Aamod Shanker, Lei Tian, Martin Sczyrba, Brid Connolly, Andrew Neureuther, and Laura Waller
  • received 07/09/2014; accepted 09/19/2014; posted 09/19/2014; Doc. ID 216606
  • [full text: PDF (1805) KB)]
  • Abstract: Traditional Transport of Intensity Equation (TIE) solvers recover phase from through-focus intensity images under the assumption that the underlying in-plane power flow is curl-free. Motivated by the study of polarization-dependent electromagnetic phase edges in lithography masks, we describe a practical situation in which this assumption breaks down. Strong absorption gradients interacting with phase edges contribute a curl to the in-plane Poynting vector, causing severe artifacts in the recovered phase. We derive how curl effects are coupled into intensity measurements and propose an iterative algorithm which both corrects the artifacts and recovers missing curl components.

Keywords (OCIS):

  • (100.5070) Image processing : Phase retrieval
  • (110.3960) Imaging systems : Microlithography
  • (080.4865) Geometric optics : Optical vortices

Procedure for measuring solar and visible properties simultaneously of glazing with complex internal or external structures

  • A. G. and G. Smith
  • received 07/11/2014; accepted 09/19/2014; posted 09/19/2014; Doc. ID 216830
  • [full text: PDF (1377) KB)]
  • Abstract: Accurate solar and visual transmittance of materials in which surfaces or internal structures are complex are often not easily amenable to standard procedures with laboratory based spectrophotometers and integrating spheres. Localized “hot spots” of intensity are common in such materials, so data on small samples is unreliable. A novel device and simple protocols have been developed and undergone validation testing. Simultaneous solar and visible transmittance and reflectance data has been acquired for skylight components and multilayer polycarbonate roof panels. The pyranometer and lux sensor set-ups also directly yield “light coolness” in Lumens/Watt. Sample areas must be large and though mainly in sheet form some testing has been done on curved panels. The instrument, its operation, and the simple calculations used are described. Results on a sub-set of diffuse and partially diffuse materials with no hot-spots have been cross-checked using 150 mm integrating spheres with spectrophotometer and the Air Mass 1.5 spectrum. Indications are that results are as good or better than with such spheres for transmittance but reflectance techniques need refinement for some sample types.

Keywords (OCIS):

  • (120.4800) Instrumentation, measurement, and metrology : Optical standards and testing
  • (160.5470) Materials : Polymers
  • (290.5880) Scattering : Scattering, rough surfaces
  • (350.6050) Other areas of optics : Solar energy
  • (150.2945) Machine vision : Illumination design

Vibrationally excited hydroxyl tagging velocimetry

  • Nathan Grady and Robert Pitz
  • received 07/16/2014; accepted 09/19/2014; posted 09/19/2014; Doc. ID 217115
  • [full text: PDF (1582) KB)]
  • Abstract: A new molecular-based velocity method is developed for high temperature flame gases based on the Hydroxyl Tagging Velocimetry (HTV) technique. In Vibrationally-Excited HTV (VE-HTV), two photons from a KrF laser (248 nm) dissociate H2O into a tag line of vibrationally excited OH (v=1). The excited state OH tag is selectively detected in a background of naturally occurring ground state OH (v=0). In atmospheric pressure laboratory burners, the OH (v=1) tag persists for 5-10 μs allowing single-shot velocity measurements along a 2 cm line under lean, stoichiometric, and rich flame conditions with temperatures reaching 2300 K. Mean velocity measurements are demonstrated in a lean (φ = 0.78) premixed H2/air turbulent flame (Re = 26,550) laboratory flame. The VE-HTV method is best suited to measure high-speed velocities in hot combustion environments in the presence of background OH.

Keywords (OCIS):

  • (120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
  • (120.1740) Instrumentation, measurement, and metrology : Combustion diagnostics
  • (120.7250) Instrumentation, measurement, and metrology : Velocimetry

One-Shot Depth Acquisition with Random Binary Pattern

  • Qin Li, Fu Li, Guangming Shi, Shan Gao, Ruodai Li, Lili Yang, and Xuemei Xie
  • received 06/19/2014; accepted 09/17/2014; posted 09/17/2014; Doc. ID 214340
  • [full text: PDF (1332) KB)]
  • Abstract: In this paper, we propose a new spatial encoding method which integrates the random binary pattern and the improved phase difference matching method to acquire a dense and precise depth map. The adopted binary pattern can simplify the pattern projecting devices compared with the colorful pattern. The density of speckles in the pattern is periodical and the positions of them are random. Based on thes two properties, we propose an improved phase-difference corresponding method which is divided into two steps: the coarse matching step to estimate the approximate coordinates of pixels in the pattern via analyzing the phase values of the image, and the fine matching step to compensate errors of the coarse matching results and to achieve sub-pixel accuracy. This matching method does not require an extra optimization method with a high computation complexity. In the experiment, we show the effectiveness of the proposed method. We also evaluate this method in actual experiments. The results show the advantages of this method compared with the TOF camera and Kinect.

Keywords (OCIS):

  • (110.6880) Imaging systems : Three-dimensional image acquisition
  • (150.5670) Machine vision : Range finding
  • (150.6910) Machine vision : Three-dimensional sensing

X-ray optics of gold nanoparticles

  • Renat Letfullin, Colin Rice, and Thomas George
  • received 07/01/2014; accepted 09/17/2014; posted 09/18/2014; Doc. ID 215102
  • [full text: PDF (489) KB)]
  • Abstract: Gold nanoparticles have been investigated as contrast agents for traditional X-ray medical procedures, utilizing the strong absorption characteristics of the nanoparticles to enhance the contrast of the detected X-ray image. Here we use the Kramers-Kronig relation for complex atomic scattering factors to find the real and imaginary parts of the index of refraction for the medium composed of single-element materials or compounds in the X-ray range of the spectrum. These complex index of refraction values are then plugged into a Lorenz-Mie theory to calculate the absorption efficiency of various size gold nanoparticles for photon energies in the 1-100 keV range. Since the output from most medical diagnostic X-ray devices follow a wide and filtered spectrum of photon energies, we introduce and compute the effective intensity-absorption-efficiency values for gold nanoparticles of radii varying from 5 to 50 nm, where we use the tungsten anode spectral model interpolating polynomials (TASMIP) model to integrate over all spectral energies generated by typical tungsten anode X-ray tubes with kilovolt potentials ranging from 50 to 150 kVp.

Keywords (OCIS):

  • (160.4760) Materials : Optical properties
  • (170.5180) Medical optics and biotechnology : Photodynamic therapy
  • (340.0340) X-ray optics : X-ray optics
  • (350.4990) Other areas of optics : Particles
  • (160.4236) Materials : Nanomaterials

Inverse Analysis of Light Scattered at a Small Angle for Characterization of a Transparent Dielectric Fiber

  • Grzegorz Swirniak, Grzegorz Glomb, and Janusz Mroczka
  • received 07/08/2014; accepted 09/17/2014; posted 09/18/2014; Doc. ID 216550
  • [full text: PDF (1232) KB)]
  • Abstract: The objective of this paper is to discuss the possibility of non-invasive, optical characterization of a transparent (glass) fiber by means of low-coherent light scattering. It will be shown, that by adjusting the coherence properties of incident light, it is possible to select these specific orders of scattering which are related to diffraction. Discussion will be devoted to both the direct scattering and the inverse problem, where an inference about diameter of a multilayered and transparent fiber is accomplished.

Keywords (OCIS):

  • (060.2270) Fiber optics and optical communications : Fiber characterization
  • (290.3200) Scattering : Inverse scattering
  • (290.5850) Scattering : Scattering, particles
  • (290.2558) Scattering : Forward scattering

Common-path and compact wavefront diagnosis system based on cross grating lateral shearing interferometer

  • Tong Ling, Yongying Yang, Xiumei Yue, Dong Liu, and Yifang Ma
  • received 08/07/2014; accepted 09/17/2014; posted 09/18/2014; Doc. ID 220528
  • [full text: PDF (1118) KB)]
  • Abstract: A common-path and compact wavefront diagnosis system for both continuous and transient wavefronts measurement is proposed based on cross grating lateral shearing interferometer (CGLSI). Derived from the basic CGLSI configuration, this system employs an aplanatic lens to convert the wavefront under test into a convergent beam, which makes it possible for CGLSI to test the wavefront of collimated beams. A geometrical optics model for grating pitch determination and a Fresnel diffraction model for order selection mask design are presented. Then a detailed analysis about the influence of the grating pitch, the distance from the cross grating to the order selection mask and the numerical aperture of the aplanatic lens on the system error is made, and a calibration method is proposed to eliminate the system error. In addition, the differential Zernike polynomials fitting method is introduced for wavefront retrieval. Before our experiment, we have designed several grating pitches and their corresponding order selection mask parameters. In the final comparative experiment with ZYGO interferometer, the wavefront diagnosis system exhibits both high precision and repeatability.

Keywords (OCIS):

  • (050.1950) Diffraction and gratings : Diffraction gratings
  • (120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
  • (120.3180) Instrumentation, measurement, and metrology : Interferometry
  • (120.5050) Instrumentation, measurement, and metrology : Phase measurement

Research on object-plane constraints and hologram expansion in phase retrieval algorithms for CW terahertz inline digital holography reconstruction

  • Jiaqi Hu, Qi Li, and Shanshan Cui
  • received 07/22/2014; accepted 09/16/2014; posted 09/17/2014; Doc. ID 217516
  • [full text: PDF (1503) KB)]
  • Abstract: In terahertz inline digital holography, the zero-order diffraction light and conjugate image cause reconstructed image misty. In this paper, three phase retrieval algorithms with different object-plane constrain are applied to conduct reconstruction under the same near-field diffraction propagation conditions and image-plane constraint. The impacts of different object-plane constraints on terahertz inline digital holographic reconstruction are studied. The results show that it is not suitable for phase retrieval algorithm to impose restriction on the phase when the object is a little complicated in the terahertz inline digital holography. In addition, the effects of zero-padding expansion, boundary replication expansion and apodization operation on reconstructed images are studied. The results indicate that the conjugate image can be eliminated and a better reconstructed image can be obtained by adopting appropriate phase retrieval algorithm after the normalized hologram extending to the minimum area which meets the applicable range of angular spectrum reconstruction algorithm by means of boundary replication.

Keywords (OCIS):

  • (090.1995) Holography : Digital holography
  • (110.6795) Imaging systems : Terahertz imaging

Luminescence enhancement in nanocomposite consisting of polyvinyl alcohol incorporated gold nanoparticles and nile blue 690 perchlorate

  • Ketevan Chubinidze, Besarion Partsvania, Tamaz Sulaberidze, Aleksandre Khuskivadze, Elene Davitashvili, and Nana Koshoridze
  • received 04/21/2014; accepted 09/15/2014; posted 09/19/2014; Doc. ID 210132
  • [full text: PDF (662) KB)]
  • Abstract: We demonstrate that the emission of visible light from the polymer matrix doped with luminescence dye and gold nanoparticles (GNPs) can be enhanced with the use of surface plasmon coupling. GNPs can enhance the luminescence of nearby luminescent dye because the interactions between the dipole moments of the dye and the surface plasmon field of the GNPs. By matching the plasmon frequency of GNPs to the frequency of pumping light source we have observed a luminescent enhancement of the nanopomposite consisting of GNPs coupled luminescent dye nile blue 690 perchlorate. Besides this enhancement depends on the distance between GNP and luminescent dye.

Keywords (OCIS):

  • (160.2540) Materials : Fluorescent and luminescent materials
  • (160.5470) Materials : Polymers
  • (160.4236) Materials : Nanomaterials

Arrange & Average algorithm for the retrieval of aerosol parameters from multiwavelength HSRL/Raman lidar data

  • Eduard Chemyakin, Detlef Muller, Sharon Burton, Alexei Kolgotin, Chris Hostetler, and Richard Ferrare
  • received 07/18/2014; accepted 09/15/2014; posted 09/16/2014; Doc. ID 213875
  • [full text: PDF (913) KB)]
  • Abstract: We present the results of a feasibility study in which a new, simple, automated and unsupervised algorithm, which we call the Arrange & Average algorithm, is used to infer microphysical parameters (complex refractive index, effective radius, total number, surface-area and volume concentrations) of atmospheric aerosol particles. The algorithm uses backscatter coefficients at 355, 532, and 1064 nm, and extinction coefficients at 355 and 532 nm as input information. Testing of the algorithm is based on synthetic optical data that are computed from prescribed monomodal particle size distributions and complex refractive indices which describe spherical, fine mode pollution particles. We tested the performance of the algorithm for the “3 backscatter (fiβ) + 2 extinction (α)” configuration of a multiwavelength aerosol HSRL or Raman lidar. We investigated the degree to which the microphysical results retrieved by this algorithm depend on the number of input backscatter and extinction coefficients. For example, we tested “3β + 1α”, “2β + 1α”, and “3βfi” lidar configurations. This Arrange & Average algorithm can be used in two ways. First, it can be applied for quick data processing of experimental data acquired with lidar. Fast automated retrievals of microphysical particle properties are needed in view of the enormous amount of data that can be acquired by the NASA Langley Research Center’s airborne “3β + 2α” high-spectral-resolution lidar (HSRL-2). It would prove useful for the growing number of ground-based multiwavelength lidar networks, and it would provide an option for analyzing the vast amount of optical data acquired with a future spaceborne multiwavelength lidar. The second potential application is to improve the microphysical particle characterization with our existing inversion algorithm that uses Tikhonov’s inversion with regularization. This advanced algorithm has recently undergone development to allow automated and unsupervised processing; the Arrange & Average can be used as a pre-classifier to further improve its speed and precision. First tests of the performance of Arrange & Average algorithm are encouraging. We used a set of 48 different monomodal particle size distributions, 4 real parts and 15 imaginary parts of the complex refractive index. All in all we tested 2880 different optical data sets for 0%, 10%, and 20% Gaussian measurement noise (one-standard deviation). In the case of the “3β + 2α” configuration with 10% measurement noise, we retrieve the particle effective radius to within 27% for 1964 (68.2%) of the test optical data sets. Number concentration is obtained to 76%, the surface-area concentration to 16%, and the volume concentration to 30% precision. The “3fiβ” configuration performs significantly poorer. The performance of the “3fiβ + 1α” and “2β + 1α” configurations is intermediate between the “3β + 2α” and the “3βfi”.

Keywords (OCIS):

  • (000.3860) General : Mathematical methods in physics
  • (010.1100) Atmospheric and oceanic optics : Aerosol detection
  • (010.1110) Atmospheric and oceanic optics : Aerosols
  • (010.3640) Atmospheric and oceanic optics : Lidar

Multi-band localized spoof plasmons in closed textured cavities

  • Bingzheng Xu, Zhuo Li, Changqing Gu, Pingping Ning, Liangliang Liu, Zhenyi Niu, and Yongjiu Zhao
  • received 07/14/2014; accepted 09/15/2014; posted 09/16/2014; Doc. ID 216983
  • [full text: PDF (867) KB)]
  • Abstract: In this work, we explore the existence of multi-band localized spoof plasmons (LSPs) in closed textured cavities with multiple groove depths. It is interesting to note that the spoof LSPs in each band resemble those generated by the textured two-dimensional (2D) cavities of the same periodicity with the corresponding single groove depth. And the field distributions and confinement characteristics of the plasmon-like modes in such a corrugated cavity are different with the conventional cavity. Hence, this multiple resonance band structures can find potential applications in the microwave and terahertz frequencies.

Keywords (OCIS):

  • (140.4780) Lasers and laser optics : Optical resonators
  • (240.6680) Optics at surfaces : Surface plasmons
  • (070.5753) Fourier optics and signal processing : Resonators

Application of Sub-Doppler DAVLL to the laser frequency stabilization in atomic cesium

  • Dian-Qiang Su, Teng-Fei Meng, Zhong-Hua Ji, Jin-Peng Yuan, Yan-Ting Zhao, Lian-Tuan Xiao, and Suo-Tang Jia
  • received 07/09/2014; accepted 09/14/2014; posted 09/15/2014; Doc. ID 216461
  • [full text: PDF (864) KB)]
  • Abstract: We achieve laser frequency stabilization by a simple technique based on Sub-Doppler dichroic atomic vapor laser lock (DAVLL) in atomic cesium. The technique that combines saturated absorption spectroscopy (SAS) and Zeeman splitting of hyperfine structure allows us to obtain a modulation-free dispersion-like error signal for frequency stabilization. For the error signal, the dependence of peak-to-peak amplitude and the slope at zero-crossing point on magnetic field is studied by simulation and experiment. Base on the result, we obtain an available Sub-Doppler DAVLL error signal with a high sensitivity to the frequency drift by selecting an appropriate strength of magnetic field. Ultimately, the fluctuation of locked laser frequency is confined below 0.5 MHz in a long term exhibiting an efficient suppression of frequency noise.

Keywords (OCIS):

  • (140.0140) Lasers and laser optics : Lasers and laser optics
  • (300.6260) Spectroscopy : Spectroscopy, diode lasers
  • (140.3425) Lasers and laser optics : Laser stabilization

Calculation of the finesse of an ideal Fabry-Pérot resonator

  • Martin Suter and Peter Dietiker
  • received 08/06/2014; accepted 09/14/2014; posted 09/15/2014; Doc. ID 220398
  • [full text: PDF (474) KB)]
  • Abstract: A new derivation of an exact finesse F for the description of an optical resonator is reported. The finesse is derived using the superposition principle of plane waves in an ideal Fabry-Pérot resonator in combination with the standard definition of the quality factor Q which relates the energy loss of a resonator cycle to the energy stored in the resonator. The derived exact expression of the finesse is compared to equations found in the literature and show that they are based on approximations. The exact finesse is then used to convert an infinite series of Lorentz-functions into the well-known Airy-equation in the case of neglected absorption. The derived expression provides a framework for the discussion of the finesse in terms of decay times, free spectral ranges and resonator line widths. The provided expression for the finesse is valid for any value of the intensity relfectivity and gives insight into the underlying physical principles of resonators.

Keywords (OCIS):

  • (230.5750) Optical devices : Resonators
  • (260.5740) Physical optics : Resonance
  • (300.6360) Spectroscopy : Spectroscopy, laser

Scalable pumping approach for extracting the maximum TEM00 solar laser power

  • Dawei Liang, Joana Almeida, and Cláudia Vistas
  • received 06/12/2014; accepted 09/14/2014; posted 09/15/2014; Doc. ID 214013
  • [full text: PDF (1106) KB)]
  • Abstract: A scalable TEM00 solar laser pumping approach is composed of four pairs of first-stage Fresnel lens-folding mirror collectors, four fused silica secondary concentrators with light guides of rectangular cross-section for radiation homogenization, four hollow two-dimensional compound parabolic concentrators (2D-CPC) for further concentration of uniform radiations from the light guides to a 3 mm diameter, 76 mm length Nd:YAG rod within four V-shaped pumping cavities. An asymmetric resonator ensures an efficient large-mode matching between pump light and oscillating laser light, 59.1W TEM00 laser power is calculated by ZEMAX© and LASCAD© numerical analysis, revealing 20 times improvement in brightness figure of merit.

Keywords (OCIS):

  • (140.0140) Lasers and laser optics : Lasers and laser optics
  • (140.3410) Lasers and laser optics : Laser resonators
  • (140.3530) Lasers and laser optics : Lasers, neodymium
  • (140.5560) Lasers and laser optics : Pumping
  • (350.6050) Other areas of optics : Solar energy
  • (350.6830) Other areas of optics : Thermal lensing

Frequency response and bandwidth in low-NA step-index plastic optical fibers

  • Svetislav Savovic, Branko Drljaca, Milan Kovacevic, Alexandar Djordjevich, Jovan Bajic, Dragan Stupar, and Grzegorz Stepniak
  • received 08/06/2014; accepted 09/12/2014; posted 09/15/2014; Doc. ID 220428
  • [full text: PDF (448) KB)]
  • Abstract: By experimental measurement and from a numerical solution to the time-dependent power flow equation, the frequency response, bandwidth, mode coupling, and mode-dependent attenuation are determined for a low-NA plastic optical fiber. Frequency response and bandwidth are specified as a function of fiber length. Numerical results are verified against experimental measurements. Mode coupling and modal attenuation are found to differ substantially between two fiber varieties of the same type (both low-NA, step-index, plastic), implying their preferential suitability that is application-specific.

Keywords (OCIS):

  • (060.2270) Fiber optics and optical communications : Fiber characterization
  • (060.2300) Fiber optics and optical communications : Fiber measurements
  • (060.2310) Fiber optics and optical communications : Fiber optics

Simplified phase recovery method in temporal speckle pattern interferometry

  • Pablo Etchepareborda, Arturo Bianchetti, Ana Laura Vadnjal, Alejandro Federico, and Guillermo Kaufmann
  • received 08/06/2014; accepted 09/11/2014; posted 09/17/2014; Doc. ID 220496
  • [full text: PDF (768) KB)]
  • Abstract: A simplified method for object phase recovering is implemented in temporal speckle pattern interferometry when the employed interferometer admits the introduction of a temporal carrier and the well known two-beam interferometry equation is verified. The spatio-temporal evolution of the object phase is isolated by modulating the acquired interferometric intensity signals with a known temporal carrier in order to carry out its analysis by using a bivariate empirical mode decomposition framework that avoids the usual application of the Hilbert transform. The advantages and limitations of this technique are analyzed and discussed by comparing with well known phase retrieval methods by means of numerical simulations and experimental data.

Keywords (OCIS):

  • (100.2000) Image processing : Digital image processing
  • (100.3010) Image processing : Image reconstruction techniques
  • (100.5070) Image processing : Phase retrieval
  • (120.6150) Instrumentation, measurement, and metrology : Speckle imaging
  • (120.5475) Instrumentation, measurement, and metrology : Pressure measurement

Development of a UV laser-induced fluorescence lidar for monitoring blue-green algae in Lake Suwa

  • Yasunori Saito, Kengo Takano, Fumitoshi Kobayashi, Kazuki Kobayashi, and Ho-Dong Park
  • received 06/05/2014; accepted 09/11/2014; posted 09/12/2014; Doc. ID 213453
  • [full text: PDF (1111) KB)]
  • Abstract: We developed a UV (355-nm) laser-induced fluorescence lidar for monitoring the real-time status of blue-green algae. Since fluorescence spectrum of blue-green algae excited by 355-nm showed the specific fluorescence at 650 nm, the lidar was designed to be able to detect the 650 nm fluorescence as a surveillance method for the algae. The usefulness was confirmed by observation at Lake Suwa over 4 years (2005 to 2008). The detection limit of the LIF lidar was 16.65 mg/L for the blue-green algae, which is the range of concentrations of the safe level set by the WHO.

Keywords (OCIS):

  • (010.3640) Atmospheric and oceanic optics : Lidar
  • (280.0280) Remote sensing and sensors : Remote sensing and sensors
  • (280.3640) Remote sensing and sensors : Lidar
  • (300.2530) Spectroscopy : Fluorescence, laser-induced
  • (010.0280) Atmospheric and oceanic optics : Remote sensing and sensors

Effects of spatio-temporal average processes on the estimation of spectral reflectance in color digital holography using speckle illuminations

  • Hideki Funamizu, Shohei Shimoma, Tomonori Yuasa, and Yoshihisa Aizu
  • received 07/09/2014; accepted 09/11/2014; posted 09/12/2014; Doc. ID 216560
  • [full text: PDF (2794) KB)]
  • Abstract: We present the effects of spatio-temporal average processes on an estimation of spectral reflectance in color digital holography using speckle illuminations. In this technique, speckle fields emitted from a multi-mode fiber are used as both a reference wave and a wavefront illuminating an object. The interference patterns of two coherent waves for three wavelengths are recorded as digital holograms on a CCD camera. Speckle fields are changed by vibrating the multi-mode fiber using a vibrator, and a number of holograms are acquired to average reconstructed images. After performing an average process, which we refer to as a temporal average process in this study, using images reconstructed from multiple holograms, a spatial average process is applied using a smoothing window function. For the estimation of spectral reflectance in reconstructed images, we use the Wiener estimation method. The effects of the average processes on color reproducibility are evaluated by a chromaticity diagram, the root-mean-square error (RMSE), and color differences.

Keywords (OCIS):

  • (100.2000) Image processing : Digital image processing
  • (300.6170) Spectroscopy : Spectra
  • (330.1690) Vision, color, and visual optics : Color
  • (330.1730) Vision, color, and visual optics : Colorimetry
  • (090.1995) Holography : Digital holography

Surface evaluation and evolution during hydrodynamic effect polishing for quartz glass

  • Wenqiang Peng, Chaoliang Guan, and Shengyi Li
  • received 06/23/2014; accepted 09/11/2014; posted 09/11/2014; Doc. ID 214314
  • [full text: PDF (4505) KB)]
  • Abstract: Hydrodynamic effect polishing (HEP), a non-contact machining process, can realize the processed surface roughness as small as atomic level. To investigate the subsurface structure, the HEP processed quartz glass surface was etched by the hydrofluoric (HF) acid solution. It has been proved that HEP is a polishing method with the ability to process the surface with atomic-level flatness and damage-free surface/subsurface. It has been found the micro plastic scratches on the lap prepolished glass have been obviously exposed when the thin redeposition layer was removed. Then the scratches were gradually removed and surface roughness decreased quickly as the removal depth increased. The surface becomes very smooth and the surface roughness maintains at an atomic level when the subsurface damage has been removed clearly. The experimental results demonstrated that the defects such as the scratches parallel to the rotational axis of the wheel were prior to be removed during the polishing process and then were the defects vertical to the wheel rotational axis.

Keywords (OCIS):

  • (160.2750) Materials : Glass and other amorphous materials
  • (220.0220) Optical design and fabrication : Optical design and fabrication
  • (220.4610) Optical design and fabrication : Optical fabrication
  • (220.5450) Optical design and fabrication : Polishing

Multiwall Carbon Nanotube-Polyvinyl Alcohol based Saturable Absorber In Passively Q-Switched Fiber Laser

  • H. Ahmad, M. F. Ismail, S. N. M. Hassan, F. Ahmad, M. Zulkifli, and S. W. Harun
  • received 07/21/2014; accepted 09/10/2014; posted 09/11/2014; Doc. ID 217211
  • [full text: PDF (802) KB)]
  • Abstract: In this work, we demonstrated compact Q-switched erbium doped fiber laser capable of generating high energy pulses using a newly developed multi-wall carbon nanotube polyvinyl alcohol (PVA) thin film based saturable absorber. Q-switched pulse operation is obtained by sandwiching the thin film between two fiber ferrules forming a saturable absorber. Saturable absorber with 1.25 wt. % of PVA concentration shows a consistency in generating pulsed laser with a good range of tunable repetition rate, shortest pulse width and produce a high pulse energy and peak power. The pulse train generated has a maximum repetition rate of 29.9 kHz with a corresponding pulse width of 3.49 μs as a function of maximum pump power of 32.15 mW. The maximum average output power of the Q-switched fiber laser system is 1.49 mW, which translates to pulse energy of 49.8 nJ. The proposed method of multiwall CNT/PVA thin film fabrication is low in cost and involves uncomplicated processes.

Keywords (OCIS):

  • (060.2410) Fiber optics and optical communications : Fibers, erbium
  • (140.3540) Lasers and laser optics : Lasers, Q-switched
  • (140.3560) Lasers and laser optics : Lasers, ring
  • (140.3538) Lasers and laser optics : Lasers, pulsed
  • (060.3510) Fiber optics and optical communications : Lasers, fiber

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