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M Franke, S Leubner, A Dubavik, A George, T Savchenko, C Pini, P Frank, D Melnikau, Y Rakovich, N Gaponik, A Eychmüller, A Richter
Microfluidic devices present the basis of modern life sciences and chemical information processing. To control the flow and to allow optical readout, a reliable sensor material that can be easily utilized for microfluidic systems is in demand. Here, we present a new optical readout system for pH sensing based on pH sensitive, photoluminescent glutathione capped cadmium telluride quantum dots that are covalently immobilized in a poly(acrylate) hydrogel. For an applicable pH sensing the generated hybrid material is integrated in a microfluidic sensor chip setup...
December 2017: Nanoscale Research Letters
Da-Peng Xu, Lin-Jie Yu, Xu-Dong Chen, Lin Chen, Qing-Qing Sun, Hao Zhu, Hong-Liang Lu, Peng Zhou, Shi-Jin Ding, David Wei Zhang
The density of oxygen vacancies characterization in high-k/metal gate is significant for semiconductor device fabrication. In this work, a new approach was demonstrated to detect the density of oxygen vacancies by in situ x-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) measurement. Moreover, the band alignment of the structure with optical band gap measured by spectroscopic ellipsometry (SE) and valence band offset by UPS were reported. The specific areal density of oxygen vacancies in high-k dielectric of HfO2/TiN was obtained by fitting the experiment data to be 8...
December 2017: Nanoscale Research Letters
Jiaqiang Li, Xiaowen Zou, Cailing Li, Jianhua Zhong, Yan Chen, Xiaoyue Zhang, Fuming Qi, Mengshuo Li, Zhiming Cai, Aifa Tang
Cancer/testis (CT) antigens are promising targets for immunotherapy due to their restricted expression in the germ cells of the testis in healthy tissue and high immunogenicity. The aim of the present study was to determine whether transmembrane protein 31 (TMEM31) is a CT antigen and to investigate the pattern of TMEM31 expression during the progression of melanoma. The pattern of expression of human TMEM31 mRNA in multiple human tissues was determined through reverse transcription-polymerase chain reaction analysis...
April 2017: Oncology Letters
Aleksey Starobor, Evgeniy Mironov, Ilya Snetkov, Oleg Palashov, Hiroaki Furuse, Shigeki Tokita, Ryo Yasuhara
The thermally induced depolarization and Verdet constant of CeF<sub>3</sub> crystals-their most important characteristics-have been studied in the 79-293 K temperature range. It has been found that thermal effects reduce substantially upon cooling down to 79 K and the Verdet constant grows in inverse proportion to the temperature. It was shown that CeF<sub>3</sub> crystals are not inferior to TGG as a medium for Faraday isolators, including cryogenic ones.
May 1, 2017: Optics Letters
Nobuhide Yokota, Ryo Igarashi, Hiroshi Yasaka
We demonstrate a simple and efficient optical Nyquist pulse generation by using a dual-electrode Mach-Zehnder modulator (MZM) driven by a combination of fundamental and second-harmonic RF signals. The method is based on a raised-cosine-shaped time filter and time lens created in the MZM under operation conditions given by a simple equation. Optical Nyquist pulses with a roll-off factor of 0.52 and intrinsic conversion efficiency of 37% are experimentally confirmed. Numerical analyses indicate that the roll-off factor can be moderately controlled down to ∼0...
May 1, 2017: Optics Letters
Ziv Glasser, Gidon Zaychik, Rita Abramov, Daniel Gotliv, Shmuel Sternklar
We describe a new technique for incoherent optical frequency domain spectroscopy (I-OFDS) that does not require measurements of the RF phase spectrum in order to reconstruct the optical spectrum. It is based on the addition of either an optical or electronic reference line to the I-OFDS system. Compared to the spectrum acquired by a regular I-OFDS system, high accuracy (error<1%) is predicted and achieved.
May 1, 2017: Optics Letters
Julius Vengelis, Vygandas Jarutis, Valdas Sirutkaitis
We present a technique for photonic crystal fiber dispersion measurement. We demonstrate that investigating supercontinuum using cross-correlation frequency resolved optical gating (XFROG) technique can be used for quantitatively characterizing dispersion and observing orthogonal polarization modes in polarization maintaining photonic crystal fibers. In addition, an XFROG trace of supercontinuum generated in a polarization maintaining photonic crystal fiber reveals complex behavior of orthogonal polarization modes that is different in normal and anomalous dispersion regions of the photonic crystal fiber...
May 1, 2017: Optics Letters
Yinwen Cao, Morteza Ziyadi, Ahmed Almaiman, Amirhossein Mohajerin-Ariaei, Peicheng Liao, Changjing Bao, Fatemeh Alishahi, Ahmad Fallahpour, Bishara Shamee, Asher J Willner, Youichi Akasaka, Tadashi Ikeuchi, Steven Wilkinson, Carsten Langrock, Martin M Fejer, Joseph Touch, Moshe Tur, Alan E Willner
An all-optical pilot-tone-based self-homodyne detection scheme using nonlinear wave mixing is experimentally demonstrated. Two scenarios are investigated using (1) multiple wavelength-division-multiplexed channels with sufficient power of the pilot tones and (2) a single channel with a low-power pilot tone. The eye diagram and bit error rate of the system are studied by tuning various parameters such as pump power, relative phase, and pilot-to-signal ratio.
May 1, 2017: Optics Letters
Gustavo Funes, Jaime Anguita
By means of an experimental setup, we study the time evolution of orbital angular momentum (OAM) crosstalk after a 5 m propagation path with a turbulence perturbation generated by a flat heater. This convective turbulence could simulate the beam passing over hot concrete or building roofs. We study the consequences of using a wide range of transmission OAM states. We also explore the effect of misalignment, and we propose two new different techniques for analyzing the vortex cancellation. Even though results are inconsistent with theoretical predictions, especially for low turbulence regimes, we state that signal-to-noise ratio is the key factor to understanding this discrepancy...
May 1, 2017: Optics Letters
Sébastien Loranger, Raman Kashyap
Many applications of optical fiber, such as specialized fiber Bragg gratings (FBGs), require high uniformity of a fiber's refractive index (RI) along its length. We show here that the mode effective index of most fibers is not constant, even on a short length scale. To help improve fiber manufacturing and selection, we demonstrate a technique for characterizing a meter length single-mode optical fiber's effective RI over a centimeter scale with a precision of 3×10<sup>-6</sup> RI units (RIUs) and an absolute accuracy of 2×10<sup>-4</sup> RIU...
May 1, 2017: Optics Letters
Junliang Dong, Alexandre Locquet, D S Citrin
This Letter presents a method for enhancing the depth resolution of terahertz deconvolution based on autoregressive (AR) spectral extrapolation. The terahertz frequency components with a high signal-to-noise ratio (SNR) are modeled with an AR process, and the missing frequency components in the regions with low SNRs are extrapolated based on the AR model. In this way, the entire terahertz frequency spectrum of the impulse response function, corresponding to the material structure, is recovered. This method, which is verified numerically and experimentally, is able to provide a "quasi-ideal" impulse response function and, therefore, greatly enhances the depth resolution for characterizing optically thin layers in the terahertz regime...
May 1, 2017: Optics Letters
Stephen C Warren-Smith, Mario Chemnitz, Henrik Schneidewind, Roman Kostecki, Heike Ebendorff-Heidepriem, Tanya M Monro, Markus A Schmidt
Intermodal third-harmonic generation using waveguides is an effective frequency conversion process due to the combination of long interaction lengths and strong modal confinement. Here we introduce the concept of tuning the third harmonic phase-matching condition via the use of dielectric nanofilms located on an open waveguide core. We experimentally demonstrate that tantalum oxide nanofilms coated onto the core of an exposed core fiber allow tuning the third harmonic wavelength over 30 nm, as confirmed by qualitative simulations...
May 1, 2017: Optics Letters
Hoang Nguyen, Md Masud Parvez Arnob, Aaron T Becker, John C Wolfe, Matthew K Hogan, Philip J Horner, Wei-Chuan Shih
A multipoint, side-firing design enables an optical fiber to output light at multiple desired locations along the fiber body. This provides advantages over traditional end-to-end fibers, especially in applications requiring fiber bundles such as brain stimulation or remote sensing. This Letter demonstrates that continuous wave (CW) laser micro-ablation can controllably create conical-shaped cavities, or side windows, for outputting light. The dimensions of these cavities determine the amount of firing light and their firing angle...
May 1, 2017: Optics Letters
Jingdan Liu, Daniel Claus, Tingfa Xu, Thorben Keßner, Alois Herkommer, Wolfgang Osten
In this Letter, we demonstrate the application of light field imaging to endoscopy. By introducing a microlens array into the image plane of a conventional endoscope, the 4D light field can be captured in one snapshot. This information can be used to obtain perspective images and to digitally refocus to different planes. These features allow for the recovery of 3D information in minimally invasive surgery. Important optical setup and performance parameters are derived to enable task specific engineering of the light field imaging system...
May 1, 2017: Optics Letters
Noor Ahmed, Ghulam Abbas Khan, Ruimin Wang, Jingru Hou, Rui Gong, Lingmeng Yang, Yanpeng Zhang
We study an optical transistor (switch and amplifier) and router by spontaneous parametric four-wave mixing and fluorescence in diamond nitrogen-vacancy (NV) center. The routing results from three peaks of fluorescence signal in the time domain, while the switching and amplification are realized by correlation and squeezing. The intensity switching speed is about 17 ns. The optical transistor and router are controlled by the power of incident beams. Our experimental results provide that the advance technique of peak division and channel equalization ratio of about 90% are applicable to all optical switching and routing...
May 1, 2017: Optics Letters
Esmaeil Mobini, Behnam Abaie, Mostafa Peysokhan, Arash Mafi
We explore the spectral properties of a capillary dye laser in the highly multimode regime. Our experiments indicate that the spectral behavior of the laser does not conform to a simple Fabry-Perot (FP) analysis; rather, it is strongly dictated by a Vernier resonant mechanism involving multiple modes, which propagate with different group velocities. The laser operates over a very broad spectral range and the Vernier effect gives rise to a free spectral range, which is orders of magnitude larger than that expected from a simple FP mechanism...
May 1, 2017: Optics Letters
Lei Wei, Nandini Bhattacharya, H Paul Urbach
We describe a method to control the directional scattering of a high-index dielectric nanosphere, which utilizes the unique focusing properties of an azimuthally polarized phase vortex and a radially polarized beam to independently excite inside the nanosphere a spinning magnetic dipole and a linearly polarized electric dipole mode normal to the magnetic dipole. We show that by simply adjusting the phase and amplitude of the field on the exit pupil of the optical system, the scattering of the nanosphere can be tuned to any direction within a plane, and the method works over a broad wavelength range...
May 1, 2017: Optics Letters
Fabio Baronio
I investigate the formation of optical localized nonlinear structures, evolving upon a non-zero background plane wave in a dispersive quadratic medium. I show the existence of quadratic Akhmediev breathers and Peregrine solitary waves in the regime of cascading second-harmonic generation. This finding opens a novel path for the excitation of extreme rogue waves and for the description of modulation instability in quadratic nonlinear optics.
May 1, 2017: Optics Letters
Jinxian Guo, L Q Chen, Peiyu Yang, Zhengjun Li, Yuan Wu, Xiaotian Feng, Chun-Hua Yuan, Z Y Ou, Weiping Zhang
In studying quantum correlation and quantum memory of continuous variables of light fields and atoms, a crucial step is the retrieval of the quantum fields by converting an atomic spin wave to light, and retrieval efficiency is a crucial parameter. In this Letter, we implement a double-pass Raman scheme in Rb87 by incorporating coherent feedback. We find that the transfer efficiency from an atomic spin wave, which is generated from a Raman process in a high gain regime, to light fields is enhanced by the double-pass scheme as compared to the commonly used single-pass scheme...
May 1, 2017: Optics Letters
Xiliang Peng, Ran Hao, Ziwei Ye, Pengfei Qin, Wenchao Chen, Hongsheng Chen, Xiaofeng Jin, Dongxiao Yang, Erping Li
We propose a highly efficient graphene-on-gap modulator (GOGM) by employing the hybrid plasmonic effect, whose modulation efficiency (up to 1.23 dB/μm after optimization) is ∼12-fold larger than that of the present graphene-on-silicon modulator (∼0.1  dB/μm). The proposed modulator has the advantage of a short modulation length of ∼3.6  μm, a relatively low insertion loss of ∼0.32  dB, and a larger modulation bandwidth of ∼0.48  THz. The physical insight is investigated, showing that both the slow light effect and the overlap between graphene and the mode field contribute...
May 1, 2017: Optics Letters
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