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https://www.readbyqxmd.com/read/29662143/observation-of-wavelength-tuning-and-bound-states-in-fiber-lasers
#1
Yang Xiang, Yiyang Luo, Bowen Liu, Zhijun Yan, Qizhen Sun, Deming Liu
We report an experimental observation of wavelength tuning and bound states in fiber lasers. A Mach-Zehnder interferometer (MZI) is adopted as an intra-cavity tunable filter to realize large-scale wavelength tuning and bandwidth controlling. By finely manipulating the MZI and intra-cavity polarization state, continuous wavelength-tunable operation from 1550.7 nm to 1580.8 nm is achieved. Meanwhile, the spectral bandwidth varying from 1.85 nm to 3.41 nm is also controlled by broadening the free spectrum range (FSR) of the MZI...
April 16, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29651039/comprehensive-modeling-of-multimode-fiber-sensors-for-refractive-index-measurement-and-experimental-validation
#2
Haris Apriyanto, Gautier Ravet, Olivier D Bernal, Michel Cattoen, Han Cheng Seat, Valérie Chavagnac, Frederic Surre, James H Sharp
We propose and develop a comprehensive model for estimating the refractive index (RI) response over three potential sensing zones in a multimode fiber. The model has been developed based on a combined ray optics, Gaussian beam, and wave optics analysis coupled to the consideration of the injected interrogating lightwave characteristics and validated experimentally through the realization of three sensors with different lengths of stripped cladding sections as the sensing region. The experimental results highly corroborate and validate the simulation output from the model for the three RI sensing zones...
April 12, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29616557/bright-single-inasp-quantum-dots-at-telecom-wavelengths-in-position-controlled-inp-nanowires-the-role-of-the-photonic-waveguide
#3
Sofiane Haffouz, Katharina D Zeuner, Dan Dalacu, Philip J Poole, Jean Lapointe, Daniel Poitras, Khaled Mnaymneh, Xiaohua Wu, Martin Couillard, Marek Korkusinski, Eva Schöll, Klaus D Jöns, Valery Zwiller, Robin L Williams
We report on the site-selected growth of bright single InAsP quantum dots embedded within InP photonic nanowire waveguides emitting at telecom wavelengths. We demonstrate a dramatic dependence of the emission rate on both the emission wavelength and the nanowire diameter. With an appropriately designed waveguide, tailored to the emission wavelength of the dot, an increase in the count rate by nearly 2 orders of magnitude (0.4 to 35 kcps) is obtained for quantum dots emitting in the telecom O-band, showing high single-photon purity with multiphoton emission probabilities down to 2%...
April 5, 2018: Nano Letters
https://www.readbyqxmd.com/read/29609349/free-space-optical-channel-characterization-and-experimental-validation-in-a-coastal-environment
#4
Wael G Alheadary, Ki-Hong Park, Nasir Alfaraj, Yujian Guo, Edgars Stegenburgs, Tien Khee Ng, Boon S Ooi, Mohamed-Slim Alouini
Over the years, free-space optical (FSO) communication has attracted considerable research interest owing to its high transmission rates via the unbounded and unlicensed bandwidths. Nevertheless, various weather conditions lead to significant deterioration of the FSO link capabilities. In this context, we report on the modelling of the channel attenuation coefficient (β) for a coastal environment and related ambient, considering the effect of coastal air temperature (T), relative humidity (RH) and dew point (TD) by employing a mobile FSO communication system capable of achieving a transmission rate of 1 Gbps at an outdoor distance of 70 m for optical beam wavelengths of 1310 nm and 1550 nm...
March 19, 2018: Optics Express
https://www.readbyqxmd.com/read/29604020/ultra-fast-all-optical-decoder-based-on-nonlinear-photonic-crystal-ring-resonators
#5
Tina Daghooghi, Mohammad Soroosh, Karim Ansari-Asl
In this paper, a 2-to-4 all-optical decoder based on photonic crystal ring resonators is introduced. The photonic crystal structure has a 2D square chalcogenide rod lattice whose maximum response time is 2 ps. Three ring resonators including nonlinear rods with 9×10-17   m2 /W for a Kerr coefficient carry out a switching operation at 1550 nm wavelength. The switching speed of the device is 500 GHz, which is more than that in previously presented works. Also, the small size of the structure is sufficient for optical integrated circuits...
March 20, 2018: Applied Optics
https://www.readbyqxmd.com/read/29601037/all-fiber-radially-azimuthally-polarized-lasers-based-on-mode-coupling-of-tapered-fibers
#6
Dong Mao, Zhiwen He, Hua Lu, Mingkun Li, Wending Zhang, Xiaoqi Cui, Biqiang Jiang, Jianlin Zhao
We demonstrate a mode converter with an insertion loss of 0.36 dB based on mode coupling of tapered single-mode and two-mode fibers, and realize all-fiber flexible cylindrical vector lasers at 1550 nm. Attributing to the continuous distribution of a tangential electric field at taper boundaries, the laser is switchable between the radially and azimuthally polarized states by adjusting the input polarization. In the temporal domain, the operation is controllable among continuous-wave, Q-switched, and mode-locked statuses by changing the saturable absorber or pump strength...
April 1, 2018: Optics Letters
https://www.readbyqxmd.com/read/29570306/dual-gated-active-metasurface-at-1550-nm-with-wide-300%C3%A2-phase-tunability
#7
Ghazaleh Kafaie Shirmanesh, Ruzan Sokhoyan, Ragip A Pala, Harry A Atwater
Active metasurfaces composed of electrically reconfigurable nanoscale subwavelength antenna arrays can enable real-time control of scattered light amplitude and phase. Achievement of widely tunable phase and amplitude in chip-based active metasurfaces operating at or near 1550 nm wavelength have considerable potential for active beam steering, dynamic hologram rendition, and realization of flat optics with reconfigurable focal lengths. Previously, electrically tunable conducting oxide-based reflectarray metasurfaces have demonstrated dynamic phase control of reflected light with a maximum phase shift of 184° (Nano Lett...
March 23, 2018: Nano Letters
https://www.readbyqxmd.com/read/29546733/measurement-of-refractive-index-of-hemoglobin-in-the-visible-nir-spectral-range
#8
Ekaterina N Lazareva, Valery V Tuchin
This study is focused on the measurements of the refractive index of hemoglobin solutions in the visible/near-infrared (NIR) spectral range at room temperature for characteristic laser wavelengths: 480, 486, 546, 589, 644, 656, 680, 930, 1100, 1300, and 1550 nm. Measurements were performed using the multiwavelength Abbe refractometer. Aqua hemoglobin solutions of different concentrations obtained from human whole blood were investigated. The specific increment of refractive index on hemoglobin concentration and the Sellmeier coefficients were calculated...
March 2018: Journal of Biomedical Optics
https://www.readbyqxmd.com/read/29543245/high-performance-chemical-vapor-deposited-graphene-on-silicon-nitride-waveguide-photodetectors
#9
Yun Gao, Guodong Zhou, Ni Zhao, Hon Ki Tsang, Chester Shu
Waveguide photodetectors integrated with graphene have demonstrated potential for ultrafast response and broadband operation. Here, we demonstrate high-performance chemical vapor deposited graphene-on-silicon nitride waveguide photodetectors by enhancing the absorption of light propagating in the transverse-magnetic mode through a metal-graphene junction. A doubling in responsivity is experimentally observed. In our zero-biased metal-graphene junction, a 15  mA W-1 intrinsic responsivity and a 30 GHz bandwidth are achieved at ∼1550  nm...
March 15, 2018: Optics Letters
https://www.readbyqxmd.com/read/29529756/comparison-of-phase-quadrature-squeezed-states-generated-from-degenerate-optical-parametric-amplifiers-using-ppktp-and-ppln
#10
Zhenju Wan, Jinxia Feng, Yuanji Li, Kuanshou Zhang
Phase quadrature squeezed states at 1550 nm generated from degenerate optical parametric amplifiers (DOPAs) using periodically poled KTiOPO4 (PPKTP) and periodically poled lithium niobate (PPLN) are compared. A squeezing of 6.8 dB was produced from the DOPA using PPKTP with the phase matching temperature of 34.5 °C. By contrast, a measured squeezing of 4.9 dB was generated using PPLN with the phase matching temperature of 135.2 °C. The degradation of squeezing using a nonlinear crystal with a high phase matching temperature is explained by a theoretical model of DOPAs including the extra phase noise caused by the guided acoustic wave Brillouin scattering within the nonlinear crystal...
March 5, 2018: Optics Express
https://www.readbyqxmd.com/read/29508537/multiband-modulation-spectroscopy-for-determination-of-sex-and-species-of-mosquitoes-in-flight
#11
Alem Gebru, Samuel Jansson, Rickard Ignell, Carsten Kirkeby, Jord C Prangsma, Mikkel Brydegaard
We present a dual-wavelength polarimetric measurement method to distinguish species and sexes of disease transmitting mosquitoes in flight. By measuring co- and de-polarized backscattered light at 808 and 1550 nm, the degree of linear polarization, wingbeat frequency, reflectance, spectral ratio and glossiness of mosquitoes can be retrieved. Body and wing contributions to these signals can be separated. Whereas the optical cross-section is sensitive to the aspect of observation, thus the heading direction of the insect in flight, we demonstrate that polarimetric- and spectral- band ratios are largely invariant to the aspect of observation...
March 5, 2018: Journal of Biophotonics
https://www.readbyqxmd.com/read/29503721/estimation-of-vegetation-water-content-at-leaf-and-canopy-level-using-dual-wavelength-commercial-terrestrial-laser-scanners
#12
Ahmed Elsherif, Rachel Gaulton, Jon Mills
Vegetation water content, quantified as the leaf equivalent water thickness (EWT), can serve as an indicator of vegetation stress. The intensity data recorded by terrestrial laser scanning (TLS) instruments, operating at shortwave infrared wavelengths, can be used to estimate the three-dimensional distribution of EWT, after a full and rigorous calibration for the range and incidence angle effects. However, TLS instruments do not record the incidence angles automatically, making calibration challenging. In this study, intensity data from two commercially available TLS instruments (Leica P40, 1550 nm shortwave infrared wavelength, and Leica P20, 808 nm near-infrared wavelength) were combined in a normalized difference index (NDI)...
April 6, 2018: Interface Focus
https://www.readbyqxmd.com/read/29495865/a-532-nm-fiber-optic-displacement-interferometer-for-low-velocity-impact-experiments
#13
Chaoqun Jiang, Yang Li, Qiancheng Liu, Xianming Zhou, S N Luo
Conventional fiber-optic displacement interferometers operated at 1550 nm suffer from low temporal or velocity resolution for lower velocity measurements. To overcome this drawback, a fiber-optic Doppler pin system operated at 532 nm is developed, and its capability is demonstrated with low-velocity plate impact experiments. The new instrument would be an important supplemental to the existed systems.
February 2018: Review of Scientific Instruments
https://www.readbyqxmd.com/read/29475327/inverse-design-of-near-unity-efficiency-perfectly-vertical-grating-couplers
#14
Andrew Michaels, Eli Yablonovitch
Efficient coupling between integrated optical waveguides and optical fibers is essential to the success of silicon photonics. While many solutions exist, perfectly vertical grating couplers that scatter light out of a waveguide in the direction normal to the waveguide's top surface are an ideal candidate due to their potential to reduce packaging complexity. Designing such couplers with high efficiencies, however, has proven difficult. In this paper, we use inverse electromagnetic design techniques to optimize a high efficiency two-layer perfectly vertical silicon grating coupler...
February 19, 2018: Optics Express
https://www.readbyqxmd.com/read/29475307/stabilization-of-self-mode-locked-quantum-dash-lasers-by-symmetric-dual-loop-optical-feedback
#15
Haroon Asghar, Wei Wei, Pramod Kumar, Ehsan Sooudi, John G McInerney
We report experimental studies of the influence of symmetric dual-loop optical feedback on the RF linewidth and timing jitter of self-mode-locked two-section quantum dash lasers emitting at 1550 nm. Various feedback schemes were investigated and optimum levels determined for narrowest RF linewidth and low timing jitter, for single-loop and symmetric dual-loop feedback. Two symmetric dual-loop configurations, with balanced and unbalanced feedback ratios, were studied. We demonstrate that unbalanced symmetric dual loop feedback, with the inner cavity resonant and fine delay tuning of the outer loop, gives the narrowest RF linewidth and reduced timing jitter over a wide range of delay, unlike single and balanced symmetric dual-loop configurations...
February 19, 2018: Optics Express
https://www.readbyqxmd.com/read/29475252/demonstration-of-a-superconducting-nanowire-single-photon-detector-with-an-ultrahigh-polarization-extinction-ratio-over-400
#16
Ruiying Xu, Yongchao Li, Fan Zheng, Guanghao Zhu, Lin Kang, Labao Zhang, Xiaoqing Jia, Xuecou Tu, Qingyuan Zhao, Biaobing Jin, Weiwei Xu, Jian Chen, Peiheng Wu
Polarization sensitive photo-detectors are the key to the implementation of the polarimetric imaging systems, which are proved to have superior performance than their traditional counterparts based on intensity discriminations. In this article, we report the demonstration of a superconducting nanowire single photon detector (SNSPD) of which the response is ultra-sensitive to the polarization state of the incident photons. Measurements carried out on a fabricated SNSPD show that a device efficiency of ~48% can be achieved at 1550 nm for the case of parallel polarization, which is ~420 times larger than that for the case of perpendicular polarization...
February 19, 2018: Optics Express
https://www.readbyqxmd.com/read/29475186/an-optofluidic-metasurface-for-lateral-flow-through-detection-of-breast-cancer-biomarker
#17
Yifei Wang, Md Azahar Ali, Edmond K C Chow, Liang Dong, Meng Lu
The rapid growth of point-of-care tests demands for biosensors with high sensitivity and small size. This paper demonstrates an optofluidic metasurface that combines silicon-on-insulator (SOI) nanophotonics and nanofluidics to realize a high-performance, lateral flow-through biosensor. The metasurface is made of a periodic array of silicon nanoposts on an SOI substrate, and functionalized with specific receptor molecules. Bonding of a polydimethylsiloxane slab directly onto the surface results in an ultracompact biosensor, where analyte solutions are restricted to flow only in the space between the nanoposts...
February 17, 2018: Biosensors & Bioelectronics
https://www.readbyqxmd.com/read/29469854/all-fiber-polarization-maintaining-erbium-doped-dispersion-managed-fiber-laser-based-on-a-nonlinear-amplifying-loop-mirror
#18
Ji Sun, Yue Zhou, Yitang Dai, Jianqiang Li, Feifei Yin, Jian Dai, Kun Xu
In this paper, we build a mode-locked all-polarization-maintaining figure-of-8 erbium-doped fiber oscillator based on a nonlinear amplifying loop mirror. The fiber oscillator can generate 1.6 ps chirped pulses that can be de-chirped to 500 fs at 1550 nm with a pulse energy of 0.8 nJ and a repetition rate of 12 MHz. It can be further amplified up to 10 nJ and compressed down to 100 fs with a pre-chirp managed nonlinear amplification setup. Such an oscillator and amplifier configuration has the advantages of self-starting and long-term operation, and it is highly suitable for subsequent frequency conversion, which is desirable for many applications in ultrafast microscopy and precision spectroscopy...
February 20, 2018: Applied Optics
https://www.readbyqxmd.com/read/29469845/inverse-design-of-optical-elements-based-on-arrays-of-dielectric-spheres
#19
Alan Zhan, Taylor K Fryett, Shane Colburn, Arka Majumdar
Arrays of wavelength scale scatterers are a promising platform for designing optical elements with a compact footprint. The large number of degrees of freedom in this system allows for unique and plentiful functionalities. However, the many variables also create a complex design problem. While intuitive forward design methods work for simple optical elements, they often fail to produce complicated elements, especially those involving multiple elements. We present an inverse design methodology for large arrays of wavelength scale spheres based on both adjoint optimization or sensitivity analysis and generalized multi-sphere Mie theory as a solution to the design problem...
February 20, 2018: Applied Optics
https://www.readbyqxmd.com/read/29425048/electro-optic-response-in-germanium-halide-perovskites
#20
Grant Walters, Edward H Sargent
Electro-optic materials that can be solution-processed and provide high crystalline quality are sought for the development of compact, efficient optical modulators. Here we present density functional theory investigations of the linear electro-optic coefficients of candidate materials cesium and methylammonium germanium halide perovskites. As with their lead halide counterparts, these compounds can be solution-processed; but in contrast, they possess the non-centrosymmetric crystal structures needed to provide a linear electro-optic effect...
February 9, 2018: Journal of Physical Chemistry Letters
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