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Optics Express

Jaka Mur, Luka Pirker, Natan Osterman, Rok Petkovšek
Laser ablation and modification using bursts of picosecond pulses and a tightly focused laser beam are used to manufacture structures in the bulk silicon. We demonstrate precise control of the surface crystallinity as well as the structure depth and topography of the processed areas, achieving homogeneous surface properties. The control is achieved with a combination of a well-defined pulse energy, systematic pulse positioning on the material, and the number of pulses in a burst. A custom designed fiber laser source is used to generate bursts of 1, 5, 10, and 20 pulses at a pulse repetition rate of 40 MHz and burst repetition rate of 83...
October 16, 2017: Optics Express
Yong Li, Yanjun Liu, Dan Luo
We demonstrate an optical thermal sensor based on cholesteric film refilled with mixture of toluene and ethanol. The thermal response mechanism is mainly based on the thermal expansion effect induce by toluene, where the ethanol is used for refractive index adjustment to determine the initial refection band position of cholesteric film. The ethanol-toluene mixture was used to adjust the color tunability with the temperature in relation with the habits of people (blue as cold, green as safe and red as hot). A broad temperature range of 86 °C and highly sensitivity of 1...
October 16, 2017: Optics Express
Tetsuya Hoshino, Norio Watanabe, Sadao Aoki, Kenji Sakurai, Masahide Itoh
We developed a versatile method for three-dimensional shape measurement where a specific particle can be selected on the substrate and its cross-sectional shape and size can be measured. A non-contact fast measurement is possible for the particle in the resonance domain. We applied rigorous coupled-wave analysis to the particle and calculated the diffraction patterns, comparing the patterns with the experimental results to obtain the size and shape. The shape and position of the focusing spot on the scattering particle was controlled precisely...
October 16, 2017: Optics Express
D Y Sergeeva, A P Potylitsyn, A A Tishchenko, M N Strikhanov
Smith-Purcell effect is well known as a source of monochromatic electromagnetic radiation. In this paper we present the generalized theory of Smith-Purcell radiation from periodic beams. The form-factors describing both coherent and incoherent regimes of radiation are calculated. The radiation characteristics are investigated in two practically important frequency ranges, THz and X-ray, for two modulation profiles, most frequently used in practice - a train of microbunches and a Gaussian-shaped one, characterized by sinusoidal modulation with an arbitrary modulation depth...
October 16, 2017: Optics Express
Xinyang Xu, Yang Qiao, Baihe Qiu
The paper presents a method aimed at accurately reconstructing transparent objects using the area source. The method called polarized light measurements (PLM) combines two reconstruction techniques: polarization analyses and light-path triangulation. The originality of this study relies on the PLM method that enables to extract the radiometric cues and geometric cues simultaneously during the surface reconstruction. To validate performance, a series of the comparison experiments are developed on different objects for the diverse thickness, material and curvature radius of unit under test...
October 16, 2017: Optics Express
Maciej Kowalczyk, Arkady Major, Jarosław Sotor
We demonstrate a high peak power mode-locked Yb:CaF2 oscillator pumped by a single-mode laser diode. The laser operated in hybrid Kerr-lens and SESAM mode-locked regime. Its performance was optimized by varying the output coupler ratio. Pulses as short as 65 fs were generated with 0.4% transmission. Employing 5% output coupler enabled generation of 77 fs pulses with 46 kW of peak power (262 mW of average output power). We believe that such high peak powers can open a way to practical applications of single-mode diode-pumped ultrafast ytterbium lasers...
October 16, 2017: Optics Express
Titas Tičkūnas, Matthieu Perrenoud, Simas Butkus, Roaldas Gadonas, Sima Rekštytė, Mangirdas Malinauskas, Domas Paipulas, Yves Bellouard, Valdas Sirutkaitis
We present a novel hybrid glass-polymer micromechanical sensor by combining two femtosecond laser direct writing processes: laser illumination followed by chemical etching of glass and two-photon polymerization. This incorporation of techniques demonstrates the capability of combining mechanical deformable devices made of silica with an integrated polymer structure for passive chemical sensing application. We demonstrate that such a sensor could be utilized for investigating the elastic properties of polymeric microstructures fabricated via the two-photon polymerization technique...
October 16, 2017: Optics Express
Yuan Feng, Ilya Vinogradov, Nien-Hui Ge
We devised a novel two-step reference scheme that can greatly suppress the additive and convolutional noises in heterodyne nonlinear spectroscopy. To optimally remove additive noise, we fully utilized the spectral correlation in multi-channel reference data through a linear combination and regression algorithm. Using our pump-probe 2D IR spectrometer, we demonstrated that our scheme can improve the signal-to-noise ratio by 10-30 times and reach the noise floor of the signal detector. The new algorithm is guaranteed to reduce noise, enables the use of unmatched reference detectors, and does not introduce baseline shift or signal distortion...
October 16, 2017: Optics Express
Mingguang Shan, Lei Liu, Zhi Zhong, Bin Liu, Guangyu Luan, Yabin Zhang
We present a dual-wavelength off-axis quasi-common-path digital holography for quantitative phase imaging using polarization-multiplexing in a single shot. Employing an off-axis nearly common-path configuration, our approach separates the two-wavelength information using a polarizing beam splitter, while modulates the orthogonal fringe directions for each wavelength using two retro-reflector mirrors, and thus generates a single multiplexed off-axis interferogram on a monochrome CCD camera. The information of a specimen, including phase and height, is reconstructed through a division algorithm for dual wavelengths with the help of a specimen-free multiplexed interferogram...
October 16, 2017: Optics Express
Paolo Bardella, Lorenzo Luigi Columbo, Mariangela Gioannini
Optical Frequency Comb (OFC) generated by semiconductor lasers are currently widely used in the extremely timely field of high capacity optical interconnects and high precision spectroscopy. In the last decade, several experimental evidences of spontaneous OFC generation have been reported in single section Quantum Dot (QD) lasers. Here we provide a physical understanding of these self-organization phenomena by simulating the multi-mode dynamics of a single section Fabry-Perot (FP) QD laser using a Time-Domain Traveling-Wave (TDTW) model that properly accounts for coherent radiation-matter interaction in the semiconductor active medium and includes the carrier grating generated by the optical standing wave pattern in the laser cavity...
October 16, 2017: Optics Express
Tian Zhang, Jian Dai, Yitang Dai, Yuting Fan, Xu Han, Jianqiang Li, Feifei Yin, Yue Zhou, Kun Xu
The dynamically tunable plasmon induced absorption (PIA) effect is demonstrated in a graphene-assisted metallodielectric grating structure. Two methods are employed to achieve the tunable PIA effect in the mid-infrared region: one is based on controlling the chemical potential of graphene by adjusting the gate voltage, the other is related to varying the refractive index of interlayer. Our calculated results reveal that high tunability in amplitude and bandwidth of the PIA effect can be achieved by using the above-mentioned methods...
October 16, 2017: Optics Express
F Giovanardi, A Cucinotta, Luca Vincetti
The potentialities in using hollow core tube lattice fibers based on inhibited coupling wave-guiding for label-free DNA detection are numerically investigated and discussed here. The proposed sensing approach does not require any additional transducer component such as Bragg gratings, amplifying techniques such as nanoparticles nor coherent sources. It simply consists of the measurement of the transmittance of a piece of fiber some ten centimeters long. In case of matching DNA sequence, an additional bio-layer is laid down the dielectric-air interface causing a red shift of the transmission spectrum of the fiber...
October 16, 2017: Optics Express
Punnag Padhy, Mohammad Asif Zaman, Paul Hansen, Lambertus Hesselink
Nanoparticles trapped on resonant near-field apertures/engravings carved in plasmonic films experience optical forces due to the steep intensity gradient field of the aperture/engraving as well as the image like interaction with the substrate. For non-resonant nanoparticles the contribution of the substrate interaction to the trapping force in the vicinity of the trap (aperture/engraving) mode is negligible. But, in the case of plasmonic nanoparticles, the contribution of the substrate interaction to the low frequency stable trapping mode of the coupled particle-trap system increases as their resonance is tuned to the trap resonance...
October 16, 2017: Optics Express
Yue Cui, Min Zhang, Danshi Wang, Siming Liu, Ze Li, Gee-Kung Chang
An effective bit-based support vector machine (SVM) is proposed as a non-parameter nonlinear mitigation approach in the millimeter-wave radio-over-fiber (RoF) mobile fronthaul (MFH) system for various modulation formats. First, we analyze the impairments originated from nonlinearities in the millimeter-wave RoF system. Then we introduce the operation principle of the bit-based SVM detector. As a classifier, the SVM can create nonlinear decision boundaries by kernel function to mitigate the distortions caused by both linear and nonlinear noise...
October 16, 2017: Optics Express
Geng Wang, Fei Xing, Minsong Wei, Zheng You
The strong stray light has huge interference on the detection of weak and small optical signals, and is difficult to suppress. In this paper, a miniaturized baffle with angled vanes was proposed and a rapid optimization model of strong light elimination was built, which has better suppression of the stray lights than the conventional vanes and can optimize the positions of the vanes efficiently and accurately. Furthermore, the light energy distribution model was built based on the light projection at a specific angle, and the light propagation models of the vanes and sidewalls were built based on the Lambert scattering, both of which act as the bias of a calculation method of stray light...
October 16, 2017: Optics Express
Fiona Thorburn, Adam Lancaster, Sean McDaniel, Gary Cook, Ajoy K Kar
A high repetition rate Q-switched modelocked ~2.1 µm monolithic waveguide laser is reported. Ultrafast laser inscription is used to fabricate 3D depressed cladding channel waveguides in holmium doped yttrium aluminium garnet. This results in a transversely single mode waveguide laser. With the use of a graphene based saturable output coupler, Q-switched modelocking was achieved with a pulse repetition frequency of 5.9 GHz and up to 170 mW of average output power. This first demonstration of multi-GHz repetition rate operation from a Ho(3+):YAG laser provides a compact and convenient source for a number of applications...
October 16, 2017: Optics Express
Sisheng Qi, Bin Zhang, Chengcheng Zhai, Yaocheng Li, Anping Yang, Yi Yu, Dingyuan Tang, Zhiyong Yang, Barry Luther-Davies
A flexible chalcogenide fiber bundle (FB) with a resolution as high as ~31 lp/mm has been fabricated for delivering thermal images of objects at room temperature. The FB is composed of ~200,000 single fibers with a Ge-As-Te-Se glass core 15 μm in diameter and a polyetherimide (PEI) cladding 16.8 μm in diameter. These Ge-As-Te-Se/PEI fibers show good transparency in the 3-12 μm spectral region. The fabricated FB presents a filling factor of ~72% and a crosstalk of ~1%. High-quality thermal images of a human hand were obtained through the FB, demonstrating good potential of the FB for longwave infrared imaging in the areas such as medicine, industry and defense...
October 16, 2017: Optics Express
Atefeh Habibpourmoghadam, Liana Lucchetti, Dean R Evans, Victor Y Reshetnyak, Faissal Omairat, Samuel L Schafforz, Alexander Lorenz
A chiral nematic (N*) liquid crystal (LC) was hybridized with a z-cut iron doped lithium niobate (Fe:LN) substrate and exposed with a focused continuous wave diode laser beam. The N* LC layer was confined with a cover glass to provide a homogeneous LC layer thickness. Two distinct kinds of test cells were investigated, one with an uncoated glass covering slip and one with an indium tin oxide (ITO) coated cover glass. Photo generated electric fields (generated in the Fe:LN) resulted in a localized defect formation and textural transitions in the N* LC...
October 16, 2017: Optics Express
Zhongming Yang, Jinyu Du, Chao Tian, Jiantai Dou, Qun Yuan, Zhishan Gao
In this paper, a generalized shift-rotation absolute measurement method is proposed to measure the absolute surface shape of high-numerical-aperture spherical surfaces. Based on the wavefront difference method, the high order misalignment aberrations can be removed from the measurements. Our generalized shift-rotation absolute measurement process only needs one rotational measurement position and one translational measurement position. A wavefront reconstruction method based on the self-adaptive differential evolution algorithm is proposed to calculate the Zernike polynomials coefficient ai of the absolute surface shape Wtest(x,y), the rotation angle Δθ, the translation δx along the x axis, and the translation δy along the y axis...
October 16, 2017: Optics Express
Feng Liang, Réal Vallée
A systematic study was performed, both experimentally and theoretically, to investigate the structural periodicity of nanogratings inscribed by focused femtosecond pulses on the surface of dielectrics. The results surprisingly show that although nanogratings generally appear periodic they are in fact intrinsically aperiodic. In the perpendicular writing scheme, the groove spacing gradually decreases from the middle part towards both sides. In the parallel writing scheme, the groove spacing varies quasiperiodically and the variation differs with respect to pulse-to-pulse spacing...
October 16, 2017: Optics Express
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