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Optics Letters

Youqiao Ma, Yousef Alattar, Jun Zhou, Mohamed Eldlio, Hiroshi Maeda, Jaromír Pištora, Michael Cada
A robust plasmonic semiconductor-based Mach-Zehnder interferometer (MZI), which consists of a semiconductor layer with a microslit flanked by two identical microgrooves, is proposed and investigated for the terahertz sensing. The microgrooves reflect the surface plasmon polariton waves toward the microslit, where they interfere with the transmitted terahertz wave. The interference pattern is determined by the permittivities of the sensing material and semiconductor (i.e., temperature dependent), making the structure useful for the refractive index (RI) and temperature detection...
June 15, 2017: Optics Letters
Ke Yin, Bin Zhang, Linyong Yang, Jing Hou
In this Letter, a high-power 1.9-4.2 μm supercontinuum (SC) laser source with a real all-fiber structure is reported. A 12 m length of ZBLAN fluoride fiber was used as the nonlinear medium, which was pumped by a thulium-doped fiber amplifier through a firm fusion-spliced joint between silica fiber and itself. The obtained SC laser had a high spectral flatness with a maximal 10 dB bandwidth of 2090 nm spanning from 1960 to 4050 nm. A record power of 15.2 W for an all-fiber mid-infrared SC laser was measured...
June 15, 2017: Optics Letters
Qiang Hao, Yunfeng Wang, Peng Luo, Hong Hu, Heping Zeng
We demonstrate a simple, but robust, self-starting environmentally stable passive harmonic mode-locked femtosecond Er-fiber laser with a scalable repetition rate of up to the 10th harmonic and >50  dB of supermode suppression. The repetition rate of short- and long-term operation for each harmonic appears to have no pulse dropout. Furthermore, at as low as 0.8 and 2.1 mHz standard deviation, the repetition rate is achieved by using the pump-induced nonlinearity to modulate the refractive index of the gain fiber...
June 15, 2017: Optics Letters
A Golinelli, X Chen, E Gontier, B Bussière, O Tcherbakoff, M Natile, P d'Oliveira, P-M Paul, J-F Hergott
We present a compact 10 kHz Ti:Sa front end relying on an original double-crystal regenerative amplifier design. This new configuration optimizes the thermal heat load management, allowing the production of a 110 nm large spectrum and maintaining a good beam profile quality. The front end delivers up to 5 W after compression, 17 fs pulses with a 170 mrad shot-to-shot residual carrier-envelope phase noise.
June 15, 2017: Optics Letters
Satyajit Maji, Maruthi M Brundavanam
A pair of stable noncanonical scalar vortices of the same charge is generated experimentally across the cross section of an optical beam using a computer-generated hologram with higher-order fractional screw dislocation. The noncanonical nature of the generated vortices is identified by the gradient of the phase around each vortex and also the crossing angle between the zero contours of the real and imaginary parts of the optical field. The anisotropy of the vortices is controlled by the fractional order of the computer-generated hologram...
June 15, 2017: Optics Letters
R Guzmán, C Gordon, L Orbe, G Carpintero
A record low-repetition rate from an on-chip monolithic InP extended cavity colliding-pulse mode-locked laser is experimentally reported. The device, fabricated in generic InP-based active-passive integration technology, makes use of integrated mirrors to enable its use as a building block within a photonic integrated circuit. This structure allows us to generate an electrical frequency comb with mode spacing of 1 GHz, determined by the 40.5 mm long resonator. Passive and hybrid mode-locking regime conditions are experimentally demonstrated...
June 15, 2017: Optics Letters
David R Carlson, Daniel D Hickstein, Alex Lind, Stefan Droste, Daron Westly, Nima Nader, Ian Coddington, Nathan R Newbury, Kartik Srinivasan, Scott A Diddams, Scott B Papp
We utilize silicon-nitride waveguides to self-reference a telecom-wavelength fiber frequency comb through supercontinuum generation, using 11.3 mW of optical power incident on the chip. This is approximately 10 times lower than conventional approaches using nonlinear fibers and is enabled by low-loss (<2  dB) input coupling and the high nonlinearity of silicon nitride, which can provide two octaves of spectral broadening with incident energies of only 110 pJ. Following supercontinuum generation, self-referencing is accomplished by mixing 780-nm dispersive-wave light with the frequency-doubled output of the fiber laser...
June 15, 2017: Optics Letters
Jie Hou, Jianji Dong, Xinliang Zhang
Systems of ordinary differential equations (SODEs) are crucial for describing the dynamic behaviors in various systems such as modern control systems which require observability and controllability. In this Letter, we propose and experimentally demonstrate an all-optical SODE solver based on the silicon-on-insulator platform. We use an add/drop microring resonator to construct two different ordinary differential equations (ODEs) and then introduce two external feedback waveguides to realize the coupling between these ODEs, thus forming the SODE solver...
June 15, 2017: Optics Letters
Ravi Kiran Attota, Haesung Park
Misalignment of the aperture diaphragm present in optical microscopes results in angular illumination asymmetry (ANILAS) at the sample plane. Here we show that through-focus propagation of ANILAS results in a lateral image shift with a focus position. This could lead to substantial errors in quantitative results for optical methods that use through-focus images such as three-dimensional nanoparticle tracking, confocal microscopy, and through-focus scanning optical microscopy (TSOM). A correlation exists between ANILAS and the slant in TSOM images...
June 15, 2017: Optics Letters
Yang Zhao, Will J Eldridge, Jason R Maher, Sanghoon Kim, Michael Crose, Mohamed Ibrahim, Howard Levinson, Adam Wax
We have developed dual-axis optical coherence tomography (DA-OCT) which enables deep tissue imaging by using a novel off-axis illumination/detection configuration. DA-OCT offers a 100-fold speed increase compared with its predecessor, multispectral multiple-scattering low coherence interferometry (ms2/LCI), by using a new beam scanning mechanism based on a microelectro-mechanical system (MEMS) mirror. The data acquisition scheme was altered to take advantage of this scanning speed, producing tomographic images at a rate of 4 frames (B-scans) per second...
June 15, 2017: Optics Letters
Pavel Zakharov
The non-ergodicity problem of temporal averaging in the laser speckle contrast imaging (LSCI) is discussed both theoretically and numerically. We demonstrate that temporal speckle statistics assessed within a finite time window might differ from the statistics of the speckle ensemble. The dependence of temporal speckle contrast on sample dynamics is non-monotonic and demonstrates regimes of negative (ergodic), as well as positive correlations with dynamics (non-ergodic). The ergodic regime is similar to an ensemble (spatial) averaging case and is typically assumed for interpretation of LSCI measurements...
June 15, 2017: Optics Letters
Anand Bahl, Vinay Pramod Majety, Armin Scrinzi, Miroslav Kolesik
Using first-principle multi-electron calculations via the hybrid anti-symmetrized coupled channels method, we create a model to describe both the nonlinear polarization and ionization of the nitrogen molecule. Based on the metastable electronic state approach, it is designed for space-and-time-resolved simulations in nonlinear optics that require modeling of optical pulses that exhibit rich spectral dynamics and propagate over long distances. As a demonstration of the model's utility, we study low-order harmonic generation in mid-infrared optical filaments...
June 15, 2017: Optics Letters
Xiu-Wen Ma, Yong-Zhen Huang, Yue-De Yang, Hai-Zhong Weng, Fu-Li Wang, Min Tang, Jin-Long Xiao, Yun Du
A compact, simple, and bistable hybrid square-rectangular laser is experimentally demonstrated as an all-optical flip-flop memory. Controllable bistability is induced by two-mode competition, together with the saturable absorption at the square microcavity section. The all-optical set and reset operations are realized by injecting signal pulses at two-mode wavelengths, with the response times of 165 and 60 ps at the triggering pulse width of 100 ps and switching energies of 2.7 and 14.2 fJ, respectively...
June 15, 2017: Optics Letters
Tetsuhiko Muroi, Yutaro Katano, Nobuhiro Kinoshita, Norihiko Ishii
To increase the reproduced data transfer rate in holographic memory, we have investigated simultaneous reproduction of two data pages. By irradiating s- and p-polarization reference beams whose angle gap is equal to the angle between the neighboring data pages in angle-multiplexed holograms, two different data pages can simultaneously be reproduced with a bit error rate low enough to decode. This technology is effective to double the data transfer rate in holographic memory.
June 15, 2017: Optics Letters
Pablo Solano, Fredrik K Fatemi, Luis A Orozco, S L Rolston
The evanescent field outside an optical nanofiber (ONF) can create optical traps for neutral atoms. We present a non-destructive method to characterize such trapping potentials. An off-resonance linearly polarized probe beam that propagates through the ONF experiences a slow axis of polarization produced by trapped atoms on opposite sides along the ONF. The transverse atomic motion is imprinted onto the probe polarization through the changing atomic index of refraction. By applying a transient impulse, we measure a time-dependent polarization rotation of the probe beam that provides both a rapid and non-destructive measurement of the optical trapping frequencies...
June 15, 2017: Optics Letters
Feng Qin, Hua Zhao, Moyang Lv, Leipeng Li, Yuan Zhou, Zhengjia Wang, Yangdong Zheng, Zhiguo Zhang, Wenwu Cao
Aiming at developing a Ho<sup>3+</sup>-based continuous-wave ultraviolet laser, the method of determining the weight of the excited-state absorption (ESA) process occupied in the populating of the D<sub>3</sub>3 level is studied. Using the rate equation model, the weight is found to be related to the weighting factors of the double-exponential decay components of the D<sub>3</sub>3 level. Using time-resolved spectroscopy, the weight of the ESA process for Y<sub>2</sub>O<sub>3</sub> ceramic doped with 0...
June 15, 2017: Optics Letters
Pavel Loiko, Petra Becker, Ladislav Bohatý, Christoph Liebald, Mark Peltz, Sophie Vernay, Daniel Rytz, Josep Maria Serres, Xavier Mateos, Yicheng Wang, Xiaodong Xu, Jun Xu, Arkady Major, Alexander Baranov, Uwe Griebner, Valentin Petrov
We studied the refractive index and dispersive properties of the tetragonal rare-earth calcium aluminates, CaLnAlO<sub>4</sub> (Ln=Gd or Y). Sellmeier equations were derived for the spectral range of 0.35-2.1 μm. The group velocity dispersion (GVD) in CaGdAlO<sub>4</sub> is positive at ∼1  μm, 95  fs<sup>2</sup>/mm and negative at ∼2  μm, -40  fs<sup>2</sup>/mm. The GVD values for CaYAlO<sub>4</sub> are similar. In addition, thermo-optic coefficients, dn/dT, and thermal coefficients of the optical path were determined for CaYAlO<sub>4</sub>...
June 15, 2017: Optics Letters
Temitope E Agbana, Hai Gong, Abena S Amoah, Vitaly Bezzubik, Michel Verhaegen, Gleb Vdovin
We have shown that the maximum achievable resolution of an in-line lensless holographic microscope is limited by aliasing and, for collimated illumination, cannot exceed the camera pixel size. This limit can be achieved only when the optimal conditions on the spatial and temporal coherence state of the illumination are satisfied. The expressions defining the configuration, delivering maximum resolution with given spatial and temporal coherence of the illumination, are obtained. The validity of these conditions is confirmed experimentally...
June 15, 2017: Optics Letters
Tsan-Wen Lu, Chia-Cheng Wu, Chun Wang, Po-Tsung Lee
We propose and demonstrate a tunable photonic crystal nanolaser consisting of 1D periodic nanorods wrapped in deformable polydimethylsiloxane. In addition to low-threshold and long-term lasing stability, the nanolaser also displays reproducible and reliable wavelength tuning with a large tunability of 7.7 nm under 1% compression. By further associating with stretching, a very wide wavelength-tunable range of 155 nm that almost spans the entire S+C+L telecommunication bands is successfully demonstrated with a single nanolaser device...
June 15, 2017: Optics Letters
Sergiy Lysenko, Valeriy Sterligov, Manuel Gonçalves, Armando Rúa, Iaroslav Gritsayenko, Félix Fernández
Angle-resolved hemispherical elastic light scattering techniques have been used to reconstruct the surface profile of two-dimensional photonic crystals with submicron resolution and metrological precision. Iterative algorithms permit subsequent calculation of a surface autocorrelation function with additional numerical approximation of the power spectrum and then yield final reconstruction of the surface shape. The proposed method enables filtering out unwanted scattering background, precluding the convergence of phase-retrieval algorithms...
June 15, 2017: Optics Letters
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