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C Li, N Krauß, G Schäfer, L Ebner, O Kliebisch, J Schmidt, S Winnerl, M Hettich, T Dekorsy
A low-cost scheme of high-speed asynchronous optical sampling based on Yb:KYW oscillators is reported. Two GHz diode-pumped oscillators with a slight pulse repetition rate offset serve as pump and probe source, respectively. The temporal resolution of this system is limited to 500 fs mainly by the pulse duration of the oscillators and also by relative timing jitter between the oscillators. A near-shot-noise noise floor around 10<sup>-6</sup> (∆R/R) is obtained within a data acquisition time of a few seconds...
April 17, 2017: Optics Express
Jingkun Guo, Richard A Norte, S Gröblacher
Mechanical oscillators are at the heart of many sensor applications. Recently several groups have developed oscillators that are probed optically, fabricated from high-stress silicon nitride films. They exhibit outstanding force sensitivities of a few aN/Hz<sup>1/2</sup> and can also be made highly reflective, for efficient detection. The optical read-out usually requires complex experimental setups, including positioning stages and bulky cavities, making them impractical for real applications. In this paper we propose a novel way of building fully integrated all-optical force sensors based on low-loss silicon nitride mechanical resonators with a photonic crystal reflector...
April 17, 2017: Optics Express
A Pospori, C A F Marques, O Bang, D J Webb, P André
We experimentally demonstrate the first polymer optical fiber Bragg grating inscribed with only one krypton fluoride laser pulse. The device has been recorded in a single-mode poly(methyl methacrylate) optical fiber, with a core doped with benzyl dimethyl ketal for photosensitivity enhancement. One laser pulse with a duration of 15 ns, which provide energy density of 974 mJ/cm<sup>2</sup>, is adequate to introduce a refractive index change of 0.74×10<sup>-4</sup> in the fiber core. After the exposure, the reflectivity of the grating increases for a few minutes following a second order exponential saturation...
April 17, 2017: Optics Express
Xiaomin Nie, Eva Ryckeboer, Gunther Roelkens, Roel Baets
We demonstrate a novel type of Fourier Transform Spectrometer (FTS) that can be realized with CMOS compatible fabrication techniques. This FTS contains no moving components and is based on the direct detection of the interferogram generated by the interference of the evanescent fields of two co-propagating waveguide modes. The theoretical analysis indicates that this type of FTS inherently has a large bandwidth (>100 nm). The first prototype that is integrated on a Si<sub>3</sub>N<sub>4</sub> waveguide platform is demonstrated and has an extremely small size (0...
April 17, 2017: Optics Express
Yuye Wang, Longhuang Tang, Degang Xu, Chao Yan, Yixin He, Jia Shi, Dexian Yan, Hongxiang Liu, Meitong Nie, Jiachen Feng, Jianquan Yao
A widely tunable, high-energy terahertz wave parametric oscillator based on 1 mol. % MgO-doped near-stoichiometric LiNbO<sub>3</sub> crystal has been demonstrated with 1064 nm nanosecond pulsed laser pumping. The tunable range of 1.16 to 4.64 THz was achieved. The maximum THz wave output energy of 17.49 μJ was obtained at 1.88 THz under the pump energy of 165 mJ/pulse, corresponding to the THz wave conversion efficiency of 1.06 × 10<sup>-4</sup> and the photon conversion efficiency of 1...
April 17, 2017: Optics Express
Yan Zhang, Yinsheng Xu, Chenyang You, Dong Xu, Junzhou Tang, Peiqing Zhang, Shixun Dai
Chemical stoichiometric Ge-As-S glasses were prepared, and their thermal properties, refractive index (n), optical bandgap, Raman gain, and femtosecond laser damage were examined. Results revealed that the n and density (ρ) of the glasses decreased as Ge concentration increased, whereas the bandgap and glass transition temperature (Tg) increased. The Raman gain coefficients (g<sub>R</sub>) of the samples were calculated on the basis of spontaneous Raman scattering spectra. g<sub>R</sub> decreased from 2...
April 17, 2017: Optics Express
Fei Xiao, Jianing Lu, Songnian Fu, Chenhui Xie, Ming Tang, Jinwen Tian, Deming Liu
Due to the non-rectangular distribution of the constellation points, traditional fast Fourier transform based frequency offset estimation (FFT-FOE) is no longer suitable for 32-QAM signal. Here, we report a modified FFT-FOE technique by selecting and digitally amplifying the inner QPSK ring of 32-QAM after the adaptive equalization, which is defined as QPSK-selection assisted FFT-FOE. Simulation results show that no FOE error occurs with a FFT size of only 512 symbols, when the signal-to-noise ratio (SNR) is above 17...
April 17, 2017: Optics Express
Chen Wei, Hongyu Luo, Hongxia Shi, YanJia Lyu, Han Zhang, Yong Liu
In this paper, we demonstrate a wavelength widely tunable gain-switched Er<sup>3+</sup>-doped ZBLAN fiber laser around 2.8 μm. The laser can be tuned over 170 nm (2699 nm~2869.9 nm) for various pump power levels, while maintaining stable μs-level single-pulse gain-switched operation with controllable output pulse duration at a selectable repetition rate. To the best of our knowledge, this is the first wavelength tunable gain-switched fiber laser in the 3 μm spectral region with the broadest tuning range (doubling the record tuning range) of the pulsed fiber lasers around 3 μm...
April 17, 2017: Optics Express
Xiaojing Huang, Weihe Xu, Evgeny Nazaretski, Nathalie Bouet, Juan Zhou, Yong S Chu, Hanfei Yan
We report scanning hard x-ray imaging with a monolithic focusing optic consisting of two multilayer Laue lenses (MLLs) bonded together. With optics pre-characterization and accurate control of the bonding process, we show that a common focal plane for both MLLs can be realized at 9.317 keV. Using bonded MLLs, we obtained a scanning transmission image of a star test pattern with a resolution of 50 × 50 nm<sup>2</sup>. By applying a ptychography algorithm, we obtained a probe size of 17 × 38 nm<sup>2</sup> and an object image with a resolution of 13 × 13 nm<sup>2</sup>...
April 17, 2017: Optics Express
Wen-Bao Sun, Xiao-Fei Yang, Zi-Bo Zhang, Wing-Han Wong, Dao-Yin Yu, Edwin Yue-Bun Pun, De-Long Zhang
Ti<sup>4+</sup>-diffused Zr<sup>4+</sup>/Er<sup>3+</sup>-codoped LiNbO<sub>3</sub> strip waveguide was fabricated on an X-cut LiNbO<sub>3</sub> substrate by thermal diffusion in sequence of Er<sup>3+</sup>, Zr<sup>4+</sup> and Ti<sup>4+</sup>. Secondary ion mass spectrometry study shows that the Ti<sup>4+</sup> ions follow a sum of two error functions in the width direction and a Gauss function in the depth direction of the waveguide...
April 17, 2017: Optics Express
Santosh Kumar, Haoquan Fan, Harald Kübler, Akbar J Jahangiri, James P Shaffer
Rydberg atom-based electrometry enables traceable electric field measurements with high sensitivity over a large frequency range, from gigahertz to terahertz. Such measurements are particularly useful for the calibration of radio frequency and terahertz devices, as well as other applications like near field imaging of electric fields. We utilize frequency modulated spectroscopy with active control of residual amplitude modulation to improve the signal to noise ratio of the optical readout of Rydberg atom-based radio frequency electrometry...
April 17, 2017: Optics Express
Borwen You, Ching-Yu Chen, Chin-Ping Yu, Tze-An Liu, Toshiaki Hattori, Ja-Yu Lu
A terahertz artificial material composed of metal rod array is experimentally investigated on its transmission spectral property and successfully incorporated into microfluidics as a miniaturized terahertz waveguide with an extended optical-path-length for label-free fluidic sensing. Theoretical and experimental characterizations of terahertz transmission spectra show that the wave guidance along the metal rod array originates from the resonance of transverse-electric-polarized waves within the metal rod slits...
April 17, 2017: Optics Express
Hidekazu Hachisu, Gérard Petit, Fumimaru Nakagawa, Yuko Hanado, Tetsuya Ido
SI-traceable measurements of optical frequencies using International Atomic Time (TAI) do not require a local primary frequency reference, but suffer from an uncertainty in tracing to the SI second. For the measurement of the <sup>87</sup>Sr lattice clock transition, we have reduced this uncertainty to the low 10<sup>-16</sup> level by averaging three sets of ten-day intermittent measurements, in which we operated the lattice clock for 10<sup>4</sup> s on each day. Moreover, a combined oscillator of two hydrogen masers was employed as a local flywheel oscillator (LFO) in order to mitigate the impact of sporadic excursion of LFO frequency...
April 17, 2017: Optics Express
Wei Quan, Kai Wei, Hairong Li
We demonstrate a novel method of measuring magnetic field based on the transient signal of the K-Rb-<sup>21</sup>Ne co-magnetometer operating in nuclear spin magnetization self-compensation magnetic field regime. The operation condition for self-compensation magnetic field by nuclear spin magnetization of <sup>21</sup>Ne in steady state is presented. We characterize the dynamics of the coupled spin ensembles by a set of Bloch equations, and formulate the expression of transient output signal...
April 17, 2017: Optics Express
Robin Vismara, Olindo Isabella, Miro Zeman
We present the optical investigation of a novel back-contacted architecture for solar cells based on a thin barium (di)silicide (BaSi<sub>2</sub>) absorber. First, through the analysis of absorption limits of different semiconducting materials, we show the potential of BaSi<sub>2</sub> for photovoltaic applications. Then, the proposed back contacted BaSi<sub>2</sub> solar cell design is investigated and optimized. An implied photocurrent density of 40.3 mA/cm<sup>2</sup> in a 1-μm thick absorber was achieved, paving the way for novel BaSi<sub>2</sub>-based thin-film solar cells...
April 17, 2017: Optics Express
Zaifa Yang, Denghui Xu, Jiayue Sun
A series of Ba<sub>3</sub>Lu(PO<sub>4</sub>)<sub>3</sub>:Sm<sup>3+</sup> phosphors were prepared by traditional high temperature solid-state reaction methods. The site-preferred occupancy of Sm<sup>3+</sup> in Ba<sub>3</sub>Lu(PO<sub>4</sub>)<sub>3</sub> and the luminescence properties of Ba<sub>3</sub>Lu(PO<sub>4</sub>)<sub>3</sub>:Sm<sup>3+</sup> were studied combined with X-ray diffraction, photoluminescence excitation (PLE) spectra, and emission (PL) spectra as well as temperature-dependent PL and decay curves...
April 17, 2017: Optics Express
Benjamin Crooke, Lachlan I W McKinna, Ivona Cetinić
Fowler's Sneaker Depth (FSD), analogous to the well known Secchi disk depth (Zsd), is a visually discerned citizen scientist metric used to assess water clarity in the Patuxent River estuary. In this study, a simple remote sensing algorithm was developed to derive FSD from space-borne spectroradiometric imagery. An empirical model was formed that estimates FSD from red-end remote sensing reflectances at 645 nm, Rrs(645). The model is based on a hyperbolic function relating water clarity to Rrs(645) that was established using radiative transfer modeling and fine tuned using in-water FSD measurements and coincident Rrs(645) data observed by NASA's Moderate Resolution Imaging Spectroradiometer aboard the Aqua spacecraft (MODISA)...
April 17, 2017: Optics Express
Yi Zhao, Ceji Fu
In this paper, we present a one-dimensional periodic microstructure for multiband selective absorbers of thermal radiation. The microstructure is made of Ag/SiO<sub>2</sub>/Ag core/shell coaxial cylinders horizontally lying on top of a SiO<sub>2</sub> dielectric spacer and an opaque silver substrate. The spectral-directional absorptivity of the proposed structure was numerically investigated with the finite element based Comsol Multiphysics software. Multiband selective absorption in the wavenumber range from 2500 to 20000 cm<sup>-1</sup> for TM-wave incidence was obtained...
April 17, 2017: Optics Express
Xiaofan Zhao, Zining Yang, Weihong Hua, Hongyan Wang, Xiaojun Xu
Although the diode pumped alkali laser (DPAL) works in a three-level scheme, higher energy-state excitation and ionization processes exist during operation, which may lead to deleterious effects on laser performance. In this paper, we report the ionization degree measurement in the gain medium of an operational hydrocarbon-free Rb DPAL by using the optogalvanic method. The results show that, at the pulsed mode with a duration of ~1 ms, a maximal ionization degree of ~0.06% is obtained at a pump power of 140 W...
April 17, 2017: Optics Express
J Ma, H H Yu, X Jiang, D S Jiang
A high-performance temperature sensor based on mode-coupling principle is proposed using a selectively filled, solid-core photonic crystal fiber with a central air-bore. The fibers are fabricated using the "stack-and-draw" method, with a micro scale central bore deliberately kept during the drawing procedure. The addition of the central air-bore enhances the mode-coupling efficiency between the fundamental core mode and modes in the high-index liquid-filled holes in the fiber cladding, therefore, the fiber can be used for a novel sensing architecture, when cladding holes are selectively filled with temperature sensitive liquids...
April 17, 2017: Optics Express
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