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Optics Letters

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https://www.readbyqxmd.com/read/28198892/stimulated-raman-scattering-microscopy-and-spectroscopy-with-a-rapid-scanning-optical-delay-line
#1
Ruoyu He, Zhiping Liu, Yongkui Xu, Wei Huang, Hong Ma, Minbiao Ji
Stimulated Raman scattering (SRS) microscopy that is capable of both high-speed imaging and rapid spectroscopy will be advantageous for detailed chemical analysis of heterogeneous biological specimens. We have developed a system based on spectral focusing SRS technology with the integration of a rapid scanning optical delay line, which allows continuous tuning of SRS spectra by scanning a galvo mirror. We demonstrate SRS spectral measurements of dimethyl sulfoxide solution at low concentrations and multi-color imaging of rice pollens and HeLa cells with line-by-line delay tuning to reduce motion artifacts, as well as fast acquisition of SRS spectra at specific regions of interest...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198891/photoacoustic-resonance-by-spatial-filtering-of-focused-ultrasound-transducers
#2
Dongyel Kang, Bahman Lashkari, Andreas Mandelis
The effect of a spherically focused ultrasound (US) transducer (TD) on photoacoustic (PA) measurements is analytically investigated using the concept of a virtual point detector. The derived analytical results indicate that the limited numerical aperture (NA) of the PA detector takes on the role of spatial filtering of the induced PA waves, which leads to the occurrence of a peak frequency in the PA spectrum. The mathematical description of this phenomenon is similar to the result of resonance peaks of light propagation in dielectrics...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198890/exact-dissipation-model-for-arbitrary-photonic-fock-state-transport-in-waveguide-qed-systems
#3
Zihao Chen, Yao Zhou, Jung-Tsung Shen
We present an exact dissipation model for correlated photon transport in waveguide QED systems. This model rigorously incorporates the infinitely many degrees of freedom of the full three-dimensional photonic scattering channels in the non-excitable ambient environment. We show that the photon leakages to the scattering channels can be accounted for by a reduced Hamiltonian and a restricted eigen-state, with a resultant atomic dissipation. This model is valid for arbitrary photonic Fock and coherent states.
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198889/single-lane-180%C3%A2-%C3%A2-gb-s-db-pam-4-signal-transmission-over-an-80%C3%A2-%C3%A2-km-dcf-free-ssmf-link
#4
Qiang Zhang, Nebojsa Stojanovic, Jinlong Wei, Changsong Xie
We experimentally demonstrate the generation and successful transmission of a single-lane 180 Gb/s (90 GBd) duo-binary four-level pulse-amplitude modulation (DB-PAM-4) signal over an 80 km standard single-mode fiber with a net data-rate of 150 Gb/s, enabled by a dual-drive Mach-Zehnder modulator-aided dispersion pre-compensation. A net data rate of 168 Gb/s is also achievable, for ranges up to 40 km. To mitigate bandwidth limitations and error spreading, pre-coded DB-PAM-4 is used; the pre-coding provides a gain of approximately 1 dB...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198888/mitigating-nonlinear-propagation-impairments-of-ultrashort-pulses-by-fractional-temporal-self-imaging
#5
Mohamed Seghilani, Reza Maram, José Azaña
We present a new approach to mitigate nonlinear impairments-mainly induced by self-phase modulation (SPM)-of high-repetition-rate optical pulses propagating through fiber-optic devices (amplifiers, propagation lines, etc.). The proposed approach is based on pulse division before nonlinear propagation, followed by pulse recombination using fractional temporal self-imaging (also known as the Talbot effect) in a dispersive medium. This approach directly addresses practical limitations of previous mitigation methods when applied to a train of pulses with a high repetition rate, in the gigahertz range and above...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198887/femtosecond-two-photon-planar-laser-induced-fluorescence-of-carbon-monoxide-in-flames
#6
Daniel R Richardson, Sukesh Roy, James R Gord
Two-photon, planar laser-induced fluorescence (TP-PLIF) of carbon monoxide was performed in steady and driven flames using femtosecond (fs) laser pulses at 1 kHz. Excitation radiation at 230.1 nm (full-width at half-maximum bandwidth of 270  cm<sup>-1</sup>) was used to pump many rovibrational two-photon transitions in the B<sup>1</sup>∑<sup>+</sup>←X<sup>1</sup>∑<sup>+</sup> system. Visible fluorescence in the range 362-516 nm was captured using an image intensifier and high-speed camera...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198886/high-performance-of-a-passively-q-switched-mid-infrared-laser-with-bi-sub-2-sub-te-sub-3-sub-graphene-composite-sa
#7
Zhenyu You, Yijian Sun, Dunlu Sun, Zaojie Zhu, Yan Wang, Jianfu Li, Chaoyang Tu, Jinlong Xu
We report passively Q-switched ∼2 and ∼3  μm mid-infrared (MIR) solid-state lasers with a self-assembly solvothermal-synthesized Bi<sub>2</sub>Te<sub>3</sub>/graphene heterostructure saturable absorber (SA) for the first time. Based on the oxidation resistance and high thermal conductivity of graphene, and large modulation depth of Bi<sub>2</sub>Te<sub>3</sub> nanosheets, two high-performance Q-switching lasers were realized. One is a Tm:YAP laser with a maximum average output power of 2...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198885/flexible-high-resolution-micro-optical-coherence-tomography-endobronchial-probe-toward-in-vivo-imaging-of-cilia
#8
Dongyao Cui, Kengyeh K Chu, Biwei Yin, Timothy N Ford, Chulho Hyun, Hui Min Leung, Joseph A Gardecki, George M Solomon, Susan E Birket, Linbo Liu, Steven M Rowe, Guillermo J Tearney
We report the design and fabrication of a flexible, longitudinally scanning high-resolution micro-optical coherence tomography (μOCT) endobronchial probe, optimized for micro-anatomical imaging in airways. The 2.4 mm diameter and flexibility of the probe allows it to be inserted into the instrument channel of a standard bronchoscope, enabling real-time video guidance of probe placement. To generate a depth-of-focus enhancing annular beam, we utilized a new fabrication method, whereby a hollow glass ferrule was angle-polished and gold-coated to produce an elongated annular reflector...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198884/characterization-of-a-liquid-filled-nodeless-anti-resonant-fiber-for-biochemical-sensing
#9
Xiao-Lu Liu, Wei Ding, Ying-Ying Wang, Shou-Fei Gao, Ling Cao, Xian Feng, Pu Wang
We theoretically and experimentally characterize a liquid-filled nodeless anti-resonant fiber (LARF) that could find versatile applications in biochemical sensing. When a hollow-core nodeless anti-resonant fiber (HARF) is filled with a low refractive index liquid such as water or aqueous solutions in the whole hollow area, it preserves its anti-resonant reflection waveguiding mechanism with attributes encompassing the broad transmission bandwidth in UV, visible, and near IR; the neglectable confinement loss; and the acceptable single-mode quality...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198883/angle-resolved-coherent-wave-mixing-using-a-4%C3%A2-%C3%A2-fs-ultra-broad-bandwidth-laser
#10
I P Mercer, T Witting, T Driver, R J Cogdell, J P Marangos, J W G Tisch
We demonstrate angle-resolved coherent (ARC) wave mixing using 4 fs light pulses derived from a laser source that spans 550-1000 nm. We believe this to be the shortest pulse duration used to date in coherent multi-dimensional spectroscopy. The marriage of this ultra-broad band, few-cycle coherent source with the ARC technique will permit new investigations of the interplay between energy transfers and quantum superposition states spanning 8200  cm<sup>-1</sup>. We applied this configuration to measurements on the photosynthetic low light (LL) complex from Rhodopseudomonas palustris in solution at ambient temperature...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198882/integrated-photonic-power-divider-with-arbitrary-power-ratios
#11
Ke Xu, Lu Liu, Xiang Wen, Wenzhao Sun, Nan Zhang, Ningbo Yi, Shang Sun, Shumin Xiao, Qinghai Song
Integrated optical power splitters are one of the fundamental building blocks in photonic integrated circuits. Conventional multimode interferometer-based power splitters are widely used as they have reasonable footprints and are easy to fabricate. However, it is challenging to realize arbitrary split ratios, especially for multi-outputs. In this Letter, an ultra-compact power splitter with a QR code-like nanostructure is designed by a nonlinear fast search method. The highly functional structure is composed of a number of freely designed square pixels with the size of 120×120  nm which could be either dielectric or air...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198881/mode-evolution-based-coupler-for-high-saturation-power-ge-on-si-photodetectors
#12
Matthew J Byrd, Erman Timurdogan, Zhan Su, Christopher V Poulton, Nicholas M Fahrenkopf, Gerald Leake, Douglas D Coolbaugh, Michael R Watts
We propose a mode-evolution-based coupler for high saturation power germanium-on-silicon photodetectors. This coupler uniformly illuminates the intrinsic germanium region of the detector, decreasing saturation effects, such as carrier screening, observed at high input powers. We demonstrate 70% more photocurrent generation (9.1-15.5 mA) and more than 40 times higher opto-electrical bandwidth (0.7-31 GHz) than conventional butt-coupled detectors under high-power illumination. The high-power and high-speed performance of the device, combined with the compactness of the coupling method, will enable new applications for integrated silicon photonics systems...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198880/proton-therapy-dosimetry-using-the-scintillation-of-the-silica-fibers
#13
Arash Darafsheh, Reza Taleei, Alireza Kassaee, Jarod C Finlay
We investigate the feasibility of proton therapy dose measurement by using scintillation of a bare silica glass fiber. The emission spectra of the optical fiber at various depths in tissue-mimicking phantoms, irradiated with proton beams of energies 100-225 MeV show two distinct peaks at 460 and 650 nm whose nature is connected with the silica point defects. Our experimental results and Monte Carlo simulation showed that the Čerenkov radiation cannot be responsible for such a phenomenon. We showed that the intensity of the peak at 650 nm correlates with the proton dose with a minimal effect of ionization quenching, while the intensity peak at 460 nm under-reports the radiation dose...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198879/picosecond-pulse-generated-supercontinuum-as-a-stable-seed-for-opcpa
#14
Lukáš Indra, František Batysta, Petr Hříbek, Jakub Novák, Zbyněk Hubka, Jonathan T Green, Roman Antipenkov, Robert Boge, Jack A Naylon, Pavel Bakule, Bedřich Rus
We present a stable supercontinuum (SC) generated in a bulk YAG crystal, pumped by 3 ps chirped pulses at 1030 nm. The SC is generated in a loose focus geometry in a 13 cm long YAG crystal, allowing for stable and robust single-filament generation. The SC energy stability exceeds that of the pump laser by almost a factor of 3. Additionally, we show that the SC spectrum has long-term stability and that the SC is coherent and compressible by compressing the portions of SC spectra close to the corresponding Fourier limit...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198878/diode-pumped-mode-locked-tm-luag-laser-at-2%C3%A2-%C3%A2-%C3%AE-m-based-on-gasb-sesam
#15
C Luan, K Yang, J Zhao, S Zhao, T Li, H Zhang, J He, L Song, T Dekorsy, M Guina, L Zheng
Mode-locking of a directly diode-pumped Tm:LuAG laser is demonstrated using GaSb-based semiconductor saturable absorber mirrors (SESAMs). Stable and self-starting mode-locked operation was realized, generating pulses as short as 13.6 ps at 2024 nm with a maximum output power of 98 mW. Two GaInAs-based SESAMs were used for comparison with the operation based upon the use of the GaSb SESAM; in this case, longer pulses with durations of 27 ps and 34 ps were obtained under the same experimental conditions. Our work sets a new record in pulse duration for mode-locked Tm:LuAG lasers and confirms that lattice-matched GaSb-based SESAMs are beneficial for mode-locked solid-state lasers in the 2 μm range...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198877/resonant-forward-scattering-of-light-by-high-refractive-index-dielectric-nanoparticles-with-toroidal-dipole-contribution
#16
Pavel D Terekhov, Kseniia V Baryshnikova, Alexander S Shalin, Alina Karabchevsky, Andrey B Evlyukhin
In this Letter, we demonstrate and investigate the Kerker-type effect in high-index dielectric nanoparticles for which the third-order multipoles give a considerable contribution to the light scattering process. It is shown that the Kerker-type effect (strong suppression of the backward light scattering and, simultaneously, resonant forward light scattering) can be associated with the resonant excitation of a toroidal dipole moment in the system. This effect is realized due to the interference of the scattered waves generated by electric, magnetic, and toroidal dipole moments of high-index nanoparticles...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198876/precise-background-subtraction-in-stimulated-emission-double-depletion-nanoscopy
#17
Peng Gao, G Ulrich Nienhaus
Low-resolution background in stimulated emission depletion (STED) nanoscopy can arise from incomplete depletion or re-excitation by the STED beam. We have recently introduced stimulated emission double depletion (STEDD), a technique to efficiently suppress this background. In STEDD, the conventional, doughnut-shaped STED pulse, which depletes excited fluorophores outside the center of the focal region, is followed by a second Gaussian STED pulse, which specifically depletes the central region. The background is removed by calculating a weighted difference of photon events collected before and after the second STED pulse...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198875/dynamic-particle-enhancement-in-limited-view-optoacoustic-tomography
#18
X Luís Deán-Ben, Lu Ding, Daniel Razansky
Limited-view artifacts are commonly present in optoacoustic tomography images, mainly due to practical geometrical and physical constraints imposed by the imaging systems. Herein, a new approach called dynamic particle-enhanced optoacoustic tomography (DPOT) is proposed for improving image contrast and visibility of optoacoustic images under limited-view scenarios. The method is based on a nonlinear combination of a temporal sequence of tomographic reconstructions representing sparsely distributed moving particles...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198874/mems-tunable-vcsels-using-2d-high-contrast-gratings
#19
Pengfei Qiao, Kun Li, Kevin T Cook, Connie J Chang-Hasnain
We demonstrate the room-temperature operation of a two-dimensional (2D) high-contrast grating (HCG) vertical-cavity surface-emitting laser (VCSEL) at 1080 nm. To the best of our knowledge, this is the first tunable electrically pumped surface-emitting laser using a 2D HCG. Our theory successfully explains the mechanism of broadband ultrahigh reflection of 2D HCGs. Our monolithic integrated laser exhibits single-mode output power above 0.68 mW under continuous-wave operation. Wavelength tunability is demonstrated via microelectromechanical system-controlled voltage...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28198873/simulating-the-space-charge-field-formation-in-thermally-poled-optical-fibers-a-new-two-rate-model-for-hydrogenated-cations
#20
Lin Huang, Honglin An, Guobin Ren, Simon Fleming
In thermally poled optical fibers, the second-order nonlinearity has been observed to be distributed in a narrow layer more than 10 μm beneath the anode surface, a result that cannot be explained by current models. In this Letter, we propose a new model based on slow migration of H<sub>3</sub>O<sup>+</sup> and fast H<sup>+</sup> migration related to the H<sub>3</sub>O<sup>+</sup> concentration. The numerical simulation results show a narrow layer-shaped distribution of the induced second-order nonlinearity, which retains its magnitude and distribution profile in the migration process, and is in good agreement with the experimental observations...
February 15, 2017: Optics Letters
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