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Optics Express

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https://www.readbyqxmd.com/read/29877498/mapping-bifurcation-structure-and-parameter-dependence-in-quantum-dot-spin-vcsels
#1
Nianqiang Li, H Susanto, B R Cemlyn, I D Henning, M J Adams
We consider a modified version of the spin-flip model (SFM) that describes optically pumped quantum dot (QD) spin-polarized vertical-cavity surface-emitting lasers (VCSELs). Maps showing different dynamical regions and those consisting of various key bifurcations are constructed by direct numerical simulations and a numerical path continuation technique, respectively. A comparison between them clarifies the physical mechanism that governs the underlying dynamics as well as routes to chaos in QD spin-VCSELs...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877497/sub-one-third-wavelength-focusing-of-surface-plasmon-polaritons-excited-by-linearly-polarized-light
#2
Jiayuan Wang, Jiasen Zhang
We report the generation of a subwavelength focal spot for surface plasmon polaritons (SPPs) by increasing the proportion of high-spatial-frequency components in the plasmonic focusing field. We have derived an analytical expression for the angular-dependent contribution of an arbitrary-shaped SPP line source to the focal field and have found that the proportion for high-spatial-frequency components can be significantly increased by launching SPPs from a horizontal line source. Accordingly, we propose a rectangular-groove plasmonic lens (PL) consisting of horizontally-arrayed central grooves and slantingly-arrayed flanking grooves on gold film...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877496/self-focusing-and-group-velocity-dispersion-of-pulsed-laser-beams-in-the-inhomogeneous-atmosphere
#3
Yuqiu Zhang, Xiaoling Ji, Hao Zhang, Xiaoqing Li, Tao Wang, Huan Wang, Yu Deng
We study self-focusing and group-velocity dispersion (GVD) effects in the inhomogeneous atmosphere on pulsed-laser space debris removal facilitated by a ground-based laser. It is found that changes of the pulse duration and the beam spot size with the propagation distance are noticeable due to the interplay of the GVD effect and the self-focusing effect, which is quite different from the behavior in the linear case. It is shown that the temporal pulse splitting may appear on the space debris, and the spatial side lobe usually appears together with the temporal pulse splitting...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877495/all-polymer-fiber-optic-ph-sensor
#4
X Cheng, J Bonefacino, B O Guan, H Y Tam
A novel all-polymer fiber-optic pH sensor using a UV-cured pH-sensitive hydrogel, poly(ethylene glycol) diacrylate (PEGDA), coated on a polymer fiber Bragg grating was developed. The PEGDA increased in volume according to the pH value of the surrounding fluid, which subsequently induced a lateral stress in the polymer fiber Bragg grating. The proposed pH sensor exhibits a pH sensitivity of up to -0.41 nm/pH and a fast response time of 30 s.
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877494/intra-pulse-laser-absorption-sensor-with-cavity-enhancement-for-oxidation-experiments-in-a-rapid-compression-machine
#5
Ehson F Nasir, Aamir Farooq
A sensor based on a mid-IR pulsed quantum cascade laser (QCL) and off-axis cavity enhanced absorption spectroscopy (OA-CEAS) has been developed for highly sensitive concentration measurements of carbon monoxide (CO) in a rapid compression machine. The duty cycle and the pulse repetition rate of the laser were optimized for increased tuning range, high chirp rate, and small line width to achieve effective laser-cavity coupling. This enabled spectrally resolved CO line-shape measurements at high pressures (P ~10 bar)...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877493/high-brightness-laser-based-on-yb-yag-mopa-chain-and-adaptive-optics-system-at-room-temperature
#6
Liu Xu, Yingchen Wu, Yinglei Du, Dan Wang, Xiangchao An, Mi Li, Tangjian Zhou, Jianli Shang, Juntao Wang, Zhangwen Liu, Long Ou, Na Zhao, Rujian Xiang, Lixin Tong, Honghuan Lin, Qingsong Gao, Yanhua Lu, Kai Zhang, Chun Tang
We demonstrate a master oscillator power amplifier (MOPA) architecture based on Yb:YAG amplifiers and adaptive optics (AO) systems with a high power and high beam quality laser output. With two conduction cooled, dual-end-pumped Yb:YAG zigzag-slab amplifiers at room temperature, the fiber laser of 300 W was scaled to 11.9 kW. Moreover, AO system positioned downstream was utilized to correct wavefront of amplified laser. The beam quality β at maximum output power was 2.8 times diffraction limited with closed-loop AO system...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877492/secured-single-pixel-broadcast-imaging
#7
Zibang Zhang, Shuming Jiao, Manhong Yao, Xiang Li, Jingang Zhong
Active single-pixel imaging (also known as illumination-modulated single-pixel imaging) employs a spatial light modulator to illuminate a scene with structured patterns. The scheme of active single-pixel imaging is similar to a wireless broadcast system, allowing that multiple receivers use a single-pixel detector to capture an image simultaneously from a different place. The use of basis patterns allows for high-quality reconstructions and an efficient sampling process, but the public knowledge of the basis patterns is not a favorable feature for security applications...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877491/topological-phases-and-the-bulk-edge-correspondence-in-2d-photonic-microring-resonator-lattices
#8
Shirin Afzal, Vien Van
We show that 2D photonic lattices consisting of coupled microring resonators can emulate quantum systems driven by periodic Hamiltonians and can thus be used to realize photonic Floquet topological insulators. By transforming a 2D microring lattice into an equivalent array of coupled waveguides with periodic boundary conditions, we explicitly derive the Floquet-Bloch Hamiltonian of the system and determine the winding numbers characterizing the band topology and bulk-edge correspondence of the lattice. By varying the coupling strengths between adjacent resonators, we show that a 2D microring lattice can support both anomalous Floquet insulator edge modes and Chern insulator edge modes over a wide range of coupling parameters...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877490/null-space-method-for-tap-value-initialization-in-constant-modulus-algorithm-for-mode-division-multiplexing-systems
#9
Junhe Zhou, Guozeng Zheng
In this paper, we propose a constant modulus algorithm (CMA) for mode division multiplexing (MDM) systems with improved convergence performance. In order to adapt to sparse channels with large differential mode group delay (DMGD) in MDM systems, the CMA adopts a variable step size similar to the improved proportionate normalized least-mean-square (IPNLMS) algorithm. In additional to that, when a singularity problem is encountered or the tap values fail to converge, it reinitializes the tap coefficients according to the tap vectors of the successfully de-multiplexed data tributaries...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877489/preliminary-measure-for-the-characterization-of-the-usefulness-of-light-sources
#10
Quang Trinh Vinh, Peter Bodrogi, Tran Quoc Khanh
A preliminary usefulness metric is defined. The metric is intended to characterize the energy efficiency of light sources in a more comprehensive way than the luminous efficacy of a source by taking selected spectral aspects of human centric lighting into consideration. The presented version of the metric is a combination of well-established measures of color quality, brightness and the circadian effect derived from the spectral power distribution of the light source. The metric includes a limited application dependence: it yields different values for interior and exterior applications, static and dynamic as well as relaxing and activating light source spectra...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877488/control-of-quasi-phase-matching-of-high-harmonics-in-a-spatially-structured-plasma
#11
Michael Wöstmann, Lukas Splitthoff, Helmut Zacharias
High-harmonic generation is widely used for providing extreme ultraviolet radiation in attosecond science. Such experiments include photoelectron spectroscopy, diffractive imaging, or the investigation of spin dynamics. Many applications are restricted by a low photon flux which originates from the low efficiency of the generation process. In this article an effective method based on the quasi-phase-matched generation of high harmonics in spatially structured, laser ablated plasma is demonstrated. Through a proper dimensioning of the plasma structure, the harmonic yield is optimized for a controllable range of harmonic orders...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877487/room-temperature-electrically-pumped-1-5-%C3%AE-m-ingaas-inalgaas-laser-monolithically-grown-on-on-axis-001-si
#12
Si Zhu, Bei Shi, Qiang Li, Kei May Lau
Hetero-epitaxial growth of high quality InP on a complementary metal-oxide-semiconductor (CMOS)-compatible Si platform is compelling for monolithic integration of optoelectronics. It will provide the combined strength of mainstream mature InP-based photonic integrated circuits (PIC) technologies and large-volume, low-cost silicon-based manufacturing foundries. Direct monolithic integration of InP-based laser diodes (LDs) on silicon helps fully exploit the potential of silicon photonics and benefits the application of dense wavelength division multiplexing (DWDM) for telecommunications...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877486/led-based-interference-reflection-microscopy-combined-with-optical-tweezers-for-quantitative-three-dimensional-microtubule-imaging
#13
Steve Simmert, Mohammad Kazem Abdosamadi, Gero Hermsdorf, Erik Schäffer
Optical tweezers combined with various microscopy techniques are a versatile tool for single-molecule force spectroscopy. However, some combinations may compromise measurements. Here, we combined optical tweezers with total-internal-reflection-fluorescence (TIRF) and interference-reflection microscopy (IRM). Using a light-emitting diode (LED) for IRM illumination, we show that single microtubules can be imaged with high contrast. Furthermore, we converted the IRM interference pattern of an upward bent microtubule to its three-dimensional (3D) profile calibrated against the optical tweezers and evanescent TIRF field...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877485/fast-optical-proximity-correction-method-based-on-nonlinear-compressive-sensing
#14
Xu Ma, Zhiqiang Wang, Yanqiu Li, Gonzalo R Arce, Lisong Dong, Javier Garcia-Frias
Optical proximity correction (OPC) is an extensively used resolution enhancement technique (RET) in optical lithography. To date, the computational efficiency has become a big issue for pixelated OPC techniques due to the increasing complexity of lithographic masks in modern integrated circuits. This paper is the first to apply nonlinear compressive sensing (CS) theory to break through the computational efficiency of gradient-based pixelated OPC methods. The proposed method reduces the dimensionality of the OPC problem by downsampling the layout pattern...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877484/high-power-generation-of-thz-from-1550-nm-photoconductive-emitters
#15
A Mingardi, W-D Zhang, E R Brown, A D Feldman, T E Harvey, R P Mirin
Two photoconductive emitters - one with a self-complementary square spiral antenna, and the other with a resonant slot antenna - were fabricated on a GaAs epilayer embedded with ErAs quantum dots. Driven with 1550 nm mode-locked lasers, ~117 μW broadband THz power was generated from the device with the spiral antenna, and ~1.2 μW from the device with resonant slot antenna. The optical-to-THz conversion is through extrinsic photoconductivity.
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877483/stimulated-emission-from-ladder-type-two-photon-coherent-atomic-ensemble
#16
Jiho Park, Han Seb Moon
We investigated the stimulated emission from a ladder-type two-photon coherent atomic ensemble, for the 5S1/2 - 5P3/2 - 5D5/2 transition of 87 Rb atoms. Under the ladder-type two-photon resonance condition obtained using pump and coupling lasers, we observed broad four-wave mixing (FWM) light stimulated from two-photon coherence induced by the seed laser coupled between the ground state of 5S1/2 and the first excited state of 5P3/2 . A dip in the FWM spectrum was obtained for three-photon resonance due to V-type two-photon coherence using the pump and seed lasers...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877482/lab-built-terrestrial-laser-scanner-self-calibration-using-mounting-angle-error-correction
#17
Xiaolu Li, Yunye Li, Xinhao Xie, Lijun Xu
Systematic errors generated from internal misalignments of a lab-built terrestrial laser scanner (TLS) need to be calibrated to improve the positional accuracy of point-cloud. Hence, an angle measurement error model was established by the ray-tracing method involving five types of mounting angle errors, which were estimated by two-face method and network method. Experimental results show that the two errors including mirror tilt error and vertical index offset error are regarded as main systematic errors for lab-built TLS, and consequently the positional accuracy of the point-cloud can be improved in horizontal and vertical directions...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877481/half-disk-laser-insight-into-the-internal-mode-structure-of-laser-resonators
#18
Prokhor A Alekseev, Mikhail S Dunaevskiy, Andrey M Monakhov, Vladislav V Dudelev, Grigorii S Sokolovskii, Richard Arinero, Roland Teissier, Alexei N Baranov
Usually electromagnetic modes inside a laser resonator are a matter of the theoretical studies. In a sense we manage "to have a look into a whispering gallery mode (WGM) resonator" and observe how the resonator modes arrange in reality. The picture occurs to be quite different from the commonly used Bessel modes in a disk resonator. A chance to explore optical modes inside a resonator appears in a WGM laser with a cleaved cavity. The flat laser facet gives an opportunity to study both far and near field patterns formed by different modes...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877480/2d-to-3d-convertible-terahertz-chiral-metamaterial-with-integrated-pneumatic-actuator
#19
Chuhuan Feng, Qi Li, Yangjian Zeng, Xin Su, Hongbin Yu
Aiming to achieve real 3D chiral metamaterial structure, a new strategy is proposed. During which a 2D to 3D conversion mechanism based on integrated pneumatic actuator is used to provide a relatively simple yet effective process solution. With this concept, only the lithography-based planar process is required, and a symmetric tuning capability over the shape of the 3D chiral metamaterial as well as its chirality both can be achieved through controlling the applied pressure. At the same time, the resultant optical activity and circular dichroism associated with this tunable 3D chiral metamaterial are also studied and exciting characteristics demonstrating enantiomeric symmetry have been successfully obtained as well...
May 28, 2018: Optics Express
https://www.readbyqxmd.com/read/29877479/adaptive-lens-free-computational-coherent-imaging-using-autofocusing-quantification-with-speckle-illumination
#20
Cheng Guo, Yixuan Zhao, Jiubin Tan, Shutian Liu, Zhengjun Liu
Multi-distance phase retrieval (MDPR) based lensfree imaging is promising for an aberration free and compact biological imaging system. In the MDPR processing, the measurement uncertainty of the sample-to-sensor distance undermines its imaging quality and imposes a heavy workload to achieve a perfect reconstruction. The optimal distance can be searched by using an image sharpness quantification function with a refocused data set, however, the scanning is sensitive to noise and aliasing artifact for MDPR. In this work, we propose an adaptive imaging scheme with the help of a diffuser inserted in the lensfree system...
May 28, 2018: Optics Express
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