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Optics Express

Benjamin R Halls, Christopher D Radke, Benjamin J Reuter, Alan L Kastengren, James R Gord, Terrence R Meyer
High-speed, two-dimensional synchrotron x-ray radiography and phase-contrast imaging are demonstrated in propulsion sprays. Measurements are performed at the 7-BM beamline at the Advanced Photon Source user facility at Argonne National Laboratory using a recently developed broadband x-ray white beam. This novel enhancement allows for high speed, high fidelity x-ray imaging for the community at large. Quantitative path-integrated liquid distributions and spatio-temporal dynamics of the sprays were imaged with a LuAG:Ce scintillator optically coupled to a high-speed CMOS camera...
January 23, 2017: Optics Express
M J Foster, J Storey, M A Zentile
A new transmission Raman spectrometer has been developed using a spatial heterodyne spectrometer (SHS), taking advantage of the high etendue inherent in this class of spectrometer to maximize the light collected from the target. The system has been tested against paracetamol tablet samples. The instrument has been shown to accept light from 0.05 mm up to a 3 mm core diameter fibre bundle with a numerical aperture of 0.22, whilst no degradation in resolution is observed.
January 23, 2017: Optics Express
Christoph Reinhardt, Tina Müller, Jack C Sankey
We present a robust sideband laser locking technique ideally suited for applications requiring low probe power and heterodyne readout. By feeding back to a high-bandwidth voltage-controlled oscillator, we lock a first-order phase-modulation sideband to a high-finesse Fabry-Perot cavity in ambient conditions, achieving a closed-loop bandwidth of 3.5 MHz (with a single integrator) limited fundamentally by the signal delay. The measured transfer function of the closed loop agrees with a simple model based on ideal system components, and from this we suggest a modified design that should achieve a bandwidth exceeding 6 MHz with a near-causally limited feedback gain as high as 4 × 10<sup>7</sup> at 1 kHz...
January 23, 2017: Optics Express
Mingguang Shan, Mikhail E Kandel, Gabriel Popescu
The refractive index distribution of cells and tissues governs their interaction with light and can report on morphological modifications associated with disease. Through intensity-based measurements, refractive index information can be extracted only via scattering models that approximate light propagation. As a result, current knowledge of refractive index distributions across various tissues and cell types remains limited. Here we use quantitative phase imaging and the statistical dispersion relation (SDR) to extract information about the refractive index variance in a variety of specimens...
January 23, 2017: Optics Express
Jin-Ling Feng, Yi-Jun Wang, Shi-Yu Liu, De-Chun Hu, Jian-Gang Lu
Multi-view three-dimensional (3-D) displays using directional beam splitter array were proposed to achieve a perfect 3-D perception with low cross-talk. The multi-direction collimated light may project different images to different viewing zones to form the multi-view autostereoscopic display. Furthermore, a high resolution 3-D display can be realized with a sequential beam splitter array and a sequential liquid crystal display. By optimization, the cross-talk of the directional beam splitter backlight system was lowered to 5% to improve the perception of the 3-D displays...
January 23, 2017: Optics Express
Jiayuan Wang, Cuiyun Chen, Zhijun Sun
We present the design of a plasmonic lens (PL) which is composed of pixelated nano-grooves on a gold film for the coupling and focusing of surface plasmon polaritons (SPPs) into multiple focal spots on the optical axis. The pixelated grooves are arranged along the y-axis and the x-position of each groove is optimized by the simulated annealing algorithm. PLs that implement two and three on-axis foci are presented and the designed structures have been validated with FDTD simulations. We also successfully constructed a long-focal-depth PL with a longitudinal FWHM of the focus that reached 25 plasmonic wavelengths, while its transverse field profile is maintained over 15 µm distance...
January 23, 2017: Optics Express
Marco A G Porcel, Florian Schepers, Jörn P Epping, Tim Hellwig, Marcel Hoekman, René G Heideman, Peter J M van der Slot, Chris J Lee, Robert Schmidt, Rudolf Bratschitsch, Carsten Fallnich, Klaus-J Boller
We demonstrate supercontinuum generation in stoichiometric silicon nitride (Si<sub>3</sub>N<sub>4</sub> in SiO<sub>2</sub>) integrated optical waveguides, pumped at telecommunication wavelengths. The pump laser is a mode-locked erbium fiber laser at a wavelength of 1.56 µm with a pulse duration of 120 fs. With a waveguide-internal pulse energy of 1.4 nJ and a waveguide with 1.0 µm × 0.9 µm cross section, designed for anomalous dispersion across the 1500 nm telecommunication range, the output spectrum extends from the visible, at around 526 nm, up to the mid-infrared, at least to 2...
January 23, 2017: Optics Express
Zhenpeng Huang, Huaqiu Deng, Changsheng Yang, Qilai Zhao, Yuanfei Zhang, Yuning Zhang, Zhouming Feng, Zhongmin Yang, Mingying Peng, Shanhui Xu
Based on a self-injection locking scheme and the nonlinear amplification effect of a semiconductor optical amplifier, a low intensity noise amplified ultrashort cavity single-frequency fiber laser at 978 nm is demonstrated with a final output power of > 230 mW and a broad temperature range of > 15 °C for single-longitudinal-mode operation. The effective cavity length of the fiber oscillator is less than 6 mm, comprising a 3.5-mm-long highly Yb<sup>3+</sup>-doped phosphate fiber and a pair of fiber Bragg gratings...
January 23, 2017: Optics Express
Meng Wang, Yujing Zhang, Zefeng Wang, Junjie Sun, Jianqiu Cao, Jinyong Leng, Xijia Gu, Xiaojun Xu
Stimulated Raman scattering (SRS) is one of the main limits for fiber lasers further power scaling. We report on the suppression of the stimulated Raman scattering in fiber laser amplifier using chirped and tilted fiber Bragg gratings (CTFBGs) for the first time. In this paper, we design and fabricate a CTFBG used to suppress the SRS in 1090 nm fiber laser output, and establish a system to test the effect of suppression. A maximum suppression ratio nearly 25 dB is achieved. Experimental results demonstrate that CTFBGs can increase the Raman threshold and promote the slope efficiency of the whole system, which is significant for further power scaling in high power oscillators and amplifiers...
January 23, 2017: Optics Express
Yuta Ooka, Tomohiro Tetsumoto, Nurul Ashikin Binti Daud, Takasumi Tanabe
We demonstrate ultrasmall demultiplexers based on photolithographic photonic crystals. The footprint of the demultiplexers is 110 μm<sup>2</sup> per channel. Our in-plane demultiplexers are clad with silica, which makes them stable and easy to integrate with other silicon photonic devices. We describe two types of demultiplexers with spacings of 136 and 267 GHz between channels for application to dense wavelength division multiplexing. Integrated titanium nitride heaters allow us to precisely control the channel wavelength...
January 23, 2017: Optics Express
Yan Zhou, Jianqiu Xu, Yulong Tang
We report a multiple-gain-element Nd:YAG laser where the gain media (three pieces of slab crystal) are alternately bonded to two optical quality 4H-SiC wafers. Such composite gain configuration can efficiently remove waste heat from the gain medium, preventing thermal lensing and heat-induced birefringence/distortion under high power laser operation. Through near Brewster's angles incidence designing and polarization discrimination, two orthogonally linearly polarized (P and S polarized) laser beams are generated simultaneously from different parts of the same system...
January 23, 2017: Optics Express
Nicolas Thiré, Raman Maksimenka, Bálint Kiss, Clément Ferchaud, Pierre Bizouard, Eric Cormier, Károly Osvay, Nicolas Forget
We demonstrate an optical parametric chirped-pulse amplifier delivering 4-cycles (38-fs) pulses centered around 3.1 µm at 100-kHz repetition rate with an average power of 4 W and an undersampled single-shot carrier-envelope phase noise of 81 mrad recorded over 25 min. The amplifier is pumped by a ~1.1 ps, Yb-YAG, thin-disk regenerative amplifier and seeded with a supercontinuum generated in bulk YAG from the same pump pulses. Carrier-envelope phase stability is passively achieved through difference-frequency generation between pump and seed pulses...
January 23, 2017: Optics Express
Wenyang Wu, Mingjie Wan, Ping Gu, Zhuo Chen, Zhenling Wang
We theoretically investigate the coupling between molecular excitons and dipolar Fano-like cavity plasmon resonance in two-layered core-shell resonators consisting of a dielectric core with high refractive index and a thin metal outer shell gapped by a low refractive index thin dielectric layer containing molecules. We demonstrate that associated with the excitation of the dipolar Fano-like cavity plasmon, the electric fields can be highly localized within the dielectric gap shell, leading to very small mode volumes...
January 23, 2017: Optics Express
B Imran Akca
In this work, a compact and ultrahigh-resolution Fourier-transform spectrometer design is presented which is in great demand in numerous areas. The spectrometer is formed by sequentially-activated 60 Mach-Zehnder interferometers that are connected to photodetectors through very-low-loss beam combiners based on two-mode interference. The long optical delays are provided by tapping the propagating light out at certain locations on the optical waveguides by using electro-optically-controlled directional couplers...
January 23, 2017: Optics Express
Shuai Hu, Taichang Gao, Hao Li, Bo Yang, Feng Zhang, Ming Chen, Lei Liu
Due to the inadequate understanding of the scattering properties of nonspherical aerosols, considerable uncertainties still exist in the radiative transfer numerical simulation. To this end, a new scattering model for nonspherical aerosols is established based on Multi-Resolution Time-Domain (MRTD) scheme. The model is comprised of three modules: near field calculation module, near-to-far transformation module and scattering parameters computation module, in which, the near electromagnetic field is calculated by MRTD technique, the near-to-far transformation scheme is performed by volume integral method, and the calculation models for extinction and absorption cross section are directly derived from Maxwell's curl equations in the frequency domain...
January 23, 2017: Optics Express
A Diebold, Z Jia, I J Graumann, Y Yin, F Emaury, C J Saraceno, X Tao, U Keller
We present the first demonstration of a thin-disk laser based on the gain material Yb:GGG. This material has many desirable properties for the thin-disk geometry: a high thermal conductivity, which is nearly independent of the doping concentration, a low quantum defect, low-temperature growth, and a broadband absorption spectrum, making it a promising contender to the well-established Yb:YAG for high-power applications. In continuous wave laser operation, we demonstrate output powers above 50 W, which is an order of magnitude higher than previously achieved with this material in the bulk geometry...
January 23, 2017: Optics Express
Hui-Chen Yeh, Szu-Wei Lee
This paper reports on the emission characteristics of amino-functionalized graphene quantum dots (af-GQDs). We employed the variable stripe length method to measure the net optical gain of af-GQDs. Photoluminescence emission was enhanced through the efficient confinement of photons using an optical resonator. The two-dimensional resonator is made up of a cholesteric liquid crystal (CLC) reflector to enable the redistribution of spontaneous emission from the af-GQDs. The proposed method was shown to increase the intensity of peak emission to more than three times that of the reference sample without a CLC reflector...
January 23, 2017: Optics Express
Makoto Oura, Johtaro Yamamoto, Takashi Jin, Masataka Kinjo
Quantum dot (QD) and quantum rod (QR) nanocrystals are widely used non-organic nanocrystals. Their strong fluorescence and photostability make them suitable for biomedical imaging applications. However, their pH-dependence and antibunching properties have not been studied much, especially in aqueous conditions. In this report, we used fluorescence correlation spectroscopy (FCS) with high temporal resolution to demonstrate that the fluorescent blinking and antibunching of QDs/QRs can be changed by varying the pH of their solutions...
January 23, 2017: Optics Express
De Cai, Zhongfei Li, Yao Li, Zhendong Guo, Sung-Liang Chen
Acoustic-resolution photoacoustic microscopy (ARPAM) plays an important role in studying the microcirculation system of biological tissues with deep penetration. High lateral resolution of ARPAM is achieved by using a high numerical aperture acoustic transducer. The deteriorated lateral resolution in the out-of-focus region can be alleviated by synthetic aperture focusing technique (SAFT). Previously, we reported a three-dimensional (3D) deconvolution ARPAM to improve both lateral and axial resolutions in the focus region...
January 23, 2017: Optics Express
Jiyong Park, Seungman Kim, Byung Soo Kim, Young-Jin Kim, Seung-Woo Kim
We present a fiber femtosecond laser oscillator that incorporates a pair of chirped fiber Bragg gratings (CFBGs) to augment the cavity length elongation produced by a PZT actuator. With a magnification factor of 18.2, the CFBG pair offers a 4.44 mm cavity length extension, providing a 25.59 kHz tuning range of the repetition rate from a 41.56 MHz nominal value without loss of mode locking. The extended tuning range enhances the performance of comb stabilization in uncontrolled environments and pulse-to-pulse interferometry for step height measurements...
January 23, 2017: Optics Express
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