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Optics Express

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https://www.readbyqxmd.com/read/29401898/mechanism-of-propagating-graphene-plasmons-excitation-for-tunable-infrared-photonic-devices
#1
Linlong Tang, Wei Wei, Xingzhan Wei, Jinpeng Nong, Chunlei Du, Haofei Shi
The mechanism of propagating graphene plasmons excitation using a nano-grating and a Fabry-Pérot cavity as the optical coupling components is studied. It is demonstrated that the system could be well described within the temporal coupled mode theory using two phenomenological parameters, namely, the intrinsic loss rate and the coupling rate of a graphene plasmonic mode, and their analytical expressions are derived. It is found that the intrinsic loss rate is solely determined by the electron relaxation time of graphene, while independent of the field distributions of the modes...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401897/artificial-dielectric-stepped-refractive-index-lens-for-the-terahertz-region
#2
A I Hernandez-Serrano, Rajind Mendis, Kimberly S Reichel, Wei Zhang, E Castro-Camus, Daniel M Mittleman
In this paper we theoretically and experimentally demonstrate a stepped-refractive-index convergent lens made of a parallel stack of metallic plates for terahertz frequencies based on artificial dielectrics. The lens consist of a non-uniformly spaced stack of metallic plates, forming a mirror-symmetric array of parallel-plate waveguides (PPWGs). The operation of the device is based on the TE1 mode of the PPWG. The effective refractive index of the TE1 mode is a function of the frequency of operation and the spacing between the plates of the PPWG...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401896/active-stabilization-of-alkali-atom-vapor-density-with-a-solid-state-electrochemical-alkali-atom-source
#3
Songbai Kang, Russell P Mott, Allison V Mis, Christopher S Roper, Elizabeth A Donley, John Kitching
We report a demonstration of vapor-phase Rubidium (Rb) density stabilization in a vapor cell using a solid-state electrochemical Rb source device. Clear Rb density stabilization is observed. Further demonstrations show that the temperature coefficient for Rb density can be reduced more than 100 times when locked and the device's power consumption is less than 10 mW. Preliminary investigation of the locking dynamic range shows that the Rb density is well stabilized when the initial density is five times higher (33 × 109 /cm3) than the set point density (6 × 109 /cm3)...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401895/megawatt-peak-power-tunable-femtosecond-source-based-on-self-phase-modulation-enabled-spectral-selection
#4
Hsiang-Yu Chung, Wei Liu, Qian Cao, Liwei Song, Franz X Kärtner, Guoqing Chang
Wavelength widely tunable femtosecond sources can be implemented by optically filtering the leftmost/rightmost spectral lobes of a broadened spectrum due to self-phase modulation (SPM) dominated fiber-optic nonlinearities. We numerically and experimentally investigate the feasibility of implementing such a tunable source inside optical fibers with negative group-velocity dispersion (GVD). We show that the spectral broadening prior to soliton fission is dominated by SPM and generates well-isolated spectral lobes; filtering the leftmost/rightmost spectral lobes results in energetic femtosecond pulses with the wavelength tuning range more than 400 nm...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401894/impact-of-substrate-etching-on-plasmonic-elements-and-metamaterials-preventing-red-shift-and-improving-refractive-index-sensitivity
#5
Yuto Moritake, Takuo Tanaka
We propose and demonstrate the elimination of substrate influence on plasmon resonance by using selective and isotropic etching of substrates. Preventing the red shift of the resonance due to substrates and improving refractive index sensitivity were experimentally demonstrated by using plasmonic nanostructures fabricated on silicon substrates. Applying substrate etching decreases the effective refractive index around the metal nanostructures, resulting in elimination of the red shift. Improvement of sensitivity to the refractive index environment was demonstrated by using plasmonic metamaterials with Fano resonance based on far field interference...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401893/semi-random-multicore-fibre-design-for-adaptive-multiphoton-endoscopy
#6
Youngchan Kim, Sean Warren, Fernando Favero, James Stone, James Clegg, Mark Neil, Carl Paterson, Jonathan Knight, Paul French, Chris Dunsby
This paper reports the development, modelling and application of a semi-random multicore fibre (MCF) design for adaptive multiphoton endoscopy. The MCF was constructed from 55 sub-units, each comprising 7 single mode cores, in a hexagonally close-packed lattice where each sub-unit had a random angular orientation. The resulting fibre had 385 single mode cores and was double-clad for proximal detection of multiphoton excited fluorescence. The random orientation of each sub-unit in the fibre reduces the symmetry of the positions of the cores in the MCF, reducing the intensity of higher diffracted orders away from the central focal spot formed at the distal tip of the fibre and increasing the maximum size of object that can be imaged...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401892/development-and-characterization-of-an-inexpensive-single-particle-fluorescence-spectrometer-for-bioaerosol-monitoring
#7
Benjamin E Swanson, J Alex Huffman
Laser-induced fluorescence (LIF) techniques to analyze atmospheric aerosols are commonly applied for research and human exposure monitoring, but are very expensive or offer poor spectral resolution. Here, we discuss how a recently proposed instrument can acquire resolved fluorescence spectra from many individual particles in a single camera image using four excitation wavelengths matched with common biological fluorophores for particle discrimination at lower cost. We discuss emission intensity calibration and demonstrate spectral differentiation among four species of pollen...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401891/six-beam-homodyne-laser-doppler-vibrometry-based-on-silicon-photonics-technology
#8
Yanlu Li, Jinghao Zhu, Matthieu Duperron, Peter O'Brien, Ralf Schüler, Soren Aasmul, Mirko de Melis, Mathias Kersemans, Roel Baets
This paper describes an integrated six-beam homodyne laser Doppler vibrometry (LDV) system based on a silicon-on-insulator (SOI) full platform technology, with on-chip photo-diodes and phase modulators. Electronics and optics are also implemented around the integrated photonic circuit (PIC) to enable a simultaneous six-beam measurement. Measurement of a propagating guided elastic wave in an aluminum plate (speed ≈ 909 m/s @ 61.5 kHz) is demonstrated.
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401890/aberration-controlled-bessel-beam-processing-of-glass
#9
Juozas Dudutis, Rokas Stonys, Gediminas Račiukaitis, Paulius Gečys
It is known that Bessel beam generation with a non-ideal axicon induces beam pattern distortions. In this paper, we introduce a simple method for non-ideal axicon-generated Bessel beam reconstruction by tilting the axicon perpendicular to its optical axis. We found an optimum axicon tilt angle where beam distortions can be compensated by inducing additional astigmatic aberrations. At optimal tilt angle, the central spot symmetry and focal depth was increased. By this method we could control crack formation symmetry in the bulk of glass, which is essential for many transparent material processing applications...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401889/understanding-and-overcoming-fundamental-limits-of-asymmetric-light-light-switches
#10
Simone Zanotto, Giuseppe Carlo La Rocca, Alessandro Tredicucci
The interplay between interference and absorption leads to interesting phenomena like coherent perfect absorption and coherent perfect transparency (CPA and CPT), which can be exploited for fully optical modulation. While it is known that it is possible to harness CPA and CPT for switching a strong signal beam with a weak control beam, it is not immediate that this process suffers from a fundamental compromise between the device efficiency (quantified by device loss and modulation depth) and the asymmetry between signal and control intensity desired for operation...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401888/spectrometer-based-refractive-index-and-dispersion-measurement-using-low-coherence-interferometry-with-confocal-scanning
#11
Daniel Francis, Helen D Ford, Ralph P Tatam
This paper describes a technique for measuring refractive index and thickness of transparent plates using a fibre-optic low-coherence interferometer. The interferometer is used to independently measure quantities related to the phase and group refractive indices, np and ng, of the material under investigation. Additionally, the dispersion of the phase index dependent quantity is measured by taking advantage of the range of wavelengths available from a broadband source. These three quantities are related to simultaneously yield np and ng as well as the geometrical thickness t of the sample...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401887/design-of-bifunctional-metasurface-based-on-independent-control-of-transmission-and-reflection
#12
Yaqiang Zhuang, Guangming Wang, Tong Cai, Qingfeng Zhang
Multifunctional metasurface integrating different functions can significantly save the occupied space, although most of bifunctional metasurfaces reported to date only control the wave in either reflection or transmission regime. In this paper, we propose a scheme that allows one to independently control the reflection and transmission wavefront under orthogonal polarizations. For demonstration, we design a bifunctional metasurface that simultaneously realizes a diffusion reflection and a focusing transmission...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401886/comparison-of-various-excitation-and-detection-schemes-for-dye-doped-polymeric-whispering-gallery-mode-micro-lasers
#13
Tobias Siegle, Jonas Kellerer, Marielle Bonenberger, Sarah Krämmer, Carolin Klusmann, Marius Müller, Heinz Kalt
We compare different excitation and collection configurations based on free-space optics and evanescently coupled tapered fibers for both lasing and fluorescence emission from dye-doped doped polymeric whispering gallery mode (WGM) micro-disk lasers. The focus of the comparison is on the lasing threshold and efficiency of light collection. With the aid of optical fibers, we localize the pump energy to the cavity-mode volume and reduce the necessary pump energy to achieve lasing by two orders of magnitude. When using fibers for detection, the collection efficiency is enhanced by four orders of magnitude compared to a free-space read-out perpendicular to the resonator plane...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401885/introduction-nonlinear-optics-nlo-2017-feature-issue
#14
David J Hagan, Cornelia Denz, Haim Suchowski, Ivan Biaggio, Mansoor Sheik-Bahae
The editors introduce the feature issue on "Nonlinear Optics 2017," based on the topics presented at the NLO 2017 conference, which was held in Waikoloa, Hawaii, USA from July 17-21, 2017. This feature issue is jointly published by Optics Express and Optical Materials Express.
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401884/effects-of-carrier-injection-profile-on-low-noise-thin-al0-85ga0-15as0-56sb0-44-avalanche-photodiodes
#15
Lucas L G Pinel, Simon J Dimler, Xinxin Zhou, Salman Abdullah, Shiyong Zhang, Chee Hing Tan, Jo Shien Ng
Avalanche photodiodes (APDs) with thin avalanche regions have shown low excess noise characteristics and high gain-bandwidth products, so they are suited for long-haul optical communications. In this work, we investigated how carrier injection profile affects the avalanche gain and excess noise factors of Al0.85Ga0.15As0.56Sb0.44 (lattice-matched to InP substrates) p-i-n and n-i-p diodes with total depletion widths of 145-240 nm. Different carrier injection profiles were achieved by using light with wavelengths of 420, 543 and 633nm...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401883/fabrication-and-characterization-of-machined-multi-core-fiber-tweezers-for-single-cell-manipulation
#16
Georgia Anastasiadi, Mark Leonard, Lynn Paterson, William N Macpherson
Optical tweezing is a non-invasive technique that can enable a variety of single cell experiments; however, it tends to be based on a high numerical aperture (NA) microscope objective to both deliver the tweezing laser light and image the sample. This introduces restrictions in system flexibility when both trapping and imaging. Here, we demonstrate a novel, high NA tweezing system based on micro-machined multicore optical fibers. Using the machined, multicore fiber tweezer, cells are optically manipulated under a variety of microscopes, without requiring a high NA objective lens...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401882/optical-design-of-soft-multifocal-contact-lens-with-uniform-optical-power-in-center-distance-zone-with-optimized-nurbs
#17
Lien T Vu, Chao-Chang A Chen, Chia-Wei Yu
This study aims to develop a new optical design method of soft multifocal contact lens (CLs) to obtain uniform optical power in large center-distance zone with optimized Non-Uniform Rational B-spline (NURBS). For the anterior surface profiles of CLs, the NURBS design curves are optimized to match given optical power distributions. Then, the NURBS in the center-distance zones are fitted in the corresponding spherical/aspheric curves for both data points and their centers of curvature to achieve the uniform power...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401881/experimental-and-numerical-comparison-of-probabilistically-shaped-4096-qam-and-a-uniformly-shaped-1024-qam-in-all-raman-amplified-160-km-transmission
#18
Seiji Okamoto, Masaki Terayama, Masato Yoshida, Keisuke Kasai, Toshihiko Hirooka, Masataka Nakazawa
We describe an experimental and numerical comparison of a probabilistically shaped (PS) 4096 QAM signal and a uniformly shaped 1024 QAM signal. Both modulation formats have the same transmission rate and a spectral efficiency of 15.3 bit/s/Hz. In the computational simulation, we compared the generalized mutual information (GMI) of both modulation formats with bit-wise soft decision decoding and bit-wise hard decision decoding. For bit-wise hard decision decoding with an overhead of 7%, a shaping gain of 1.8 dB was attained...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401880/electrical-characteristics-of-silicon-nanowire-cmos-inverters-under-illumination
#19
Jeuk Yoo, Yoonjoong Kim, Doohyeok Lim, Sangsig Kim
In this study, we examine the electrical characteristics of complementary metal-oxide-semiconductor (CMOS) inverters with silicon nanowire (SiNW) channels on transparent substrates under illumination. The electrical characteristics vary with the wavelength and power of light due to the variation in the generation rates of the electric-hole pairs. Compared to conventional optoelectronic devices that sense the on/off states by the variation in the current, our device achieves the sensing of the on/off states with more precision by using the voltage variation induced by the wavelength or intensity of light...
February 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29401879/high-power-high-brightness-980-nm-lasers-with-50-wall-plug-efficiency-based-on-asymmetric-super-large-optical-cavity
#20
Shaoyu Zhao, Aiyi Qi, Mingjin Wang, Hongwei Qu, Yuzhe Lin, Fengxin Dong, Wanhua Zheng
High-power high-brightness super large optical cavity laser diodes with an optimized epitaxial structure are investigated at the wavelength of 980 nm range. The thicknesses of P- and N-waveguides are prudently chosen based on a systematic consideration about mode characteristics and vertical far-field divergences. Broad area laser diodes show a high internal quantum efficiency of 98% and a low internal optical loss of 0.58 cm-1. The ridge-waveguide laser with 7 μm ridge and 3 mm cavity yields 1.9 W single spatial mode output with far-field divergence angles of 6...
February 5, 2018: Optics Express
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