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Optics Letters

Shou-Fei Gao, Ying-Ying Wang, Wei Ding, Pu Wang
UV guiding fibers are highly sought after in laser and spectroscopy applications. Recent advances in hollow-core fiber orient a practical approach for proper UV light delivery sustainable to high-power and long-term irradiation. In this Letter, we report two types of hollow-core negative-curvature fibers (NCFs) in a UV spectral range. Their structures consist of one ring of six small (7.9 μm in diameter) and four big (20.8 μm in diameter) tubes, enclosing a hollow core of similar size (∼15  μm in diameter)...
March 15, 2018: Optics Letters
Osamu Takayama, Graciana Puentes
We demonstrate experimentally the lateral circular birefringence of a tunable birefringent polymer, the first example of the spin Hall effect of light in a polymeric material, and we demonstrate that this light shift can be significantly enhanced by tuning the effective birefringence in the polymer. We report experimental observations of this effect using polarimetric techniques and quantum-weak-measurement techniques, reporting a weak amplification factor of 200.
March 15, 2018: Optics Letters
Pavel Honzatko, Yauhen Baravets, Ashwin Kumar Myakalwar
We present a broadly tunable single-frequency ytterbium-doped fiber laser. Its broadband tunability is made possible by low resonator losses. The wavelength is determined by a grating filter, while the single-frequency regime is achieved by filtering the longitudinal modes in a fiber ring resonance filter. We obtained a tuning range from 1023 nm to 1107 nm. A feedback loop driving a fiber stretcher actuated by a piezo-element prevents mode hopping. Based on the coherent delayed self-heterodyne interferometry, the laser linewidth is estimated to be 600 Hz with feedback open and 11...
March 15, 2018: Optics Letters
Ondřej Novák, Peter R Krogen, Tobias Kroh, Tomáš Mocek, Franz X Kärtner, Kyung-Han Hong
We report on a femtosecond ∼8.5  μm, ∼2  μJ source based on the intrapulse difference-frequency generation (DFG) of 2.1 μm pulses in an AgGaSe2 (AGSe) crystal. Compared to the conventional ∼0.8 or 1 μm near-infrared (IR) pulses, a ∼2  μm driver for intrapulse DFG can provide more efficient conversion into the wavelengths longer than 5 μm due to a lower quantum defect and is more suitable for the non-oxide nonlinear crystals that have a relatively low bandgap energy. Using 26 fs, 2...
March 15, 2018: Optics Letters
Aaron M Michalko, James R Fienup
Transverse translation diverse phase retrieval (TTDPR), a ptychographic image-based wavefront-sensing technique, is a viable method for optical shop testing due to its high accuracy and relatively simple experimental arrangement. However, when measuring a reflective optic, a normally hard-edged translating illumination will become soft-edged due to diffraction, which may reduce the accuracy of TTDPR by suppressing fine structures in measured data. In this Letter, we quantitatively explore the wavefront-sensing accuracy of TTDPR in the presence of soft-edged translating illumination...
March 15, 2018: Optics Letters
A A Voronin, A A Lanin, A A Fedotov, A M Zheltikov
Quantitative characterization of dispersion near molecular resonances is difficult both conceptually and technically, as it requires systematic measurements of rapidly varying dispersion profiles across the edges of molecular absorption bands. Here, we show that this challenge can be confronted with an ultrafast spectrochronography technique that combines time-resolved four-wave mixing and cross-correlation frequency-resolved optical gating. We demonstrate that, with the spectrum of an ultrashort mid-infrared laser probe stretching across the edge of a molecular absorption band, the Wigner chronocyclic maps of such a probe reveal universal signatures of anomalous dispersion and help quantify such dispersion anomalies...
March 15, 2018: Optics Letters
Junxiang Ke, Lilin Yi, Guangqiong Xia, Weisheng Hu
For the first time, to the best of our knowledge, we experimentally demonstrate a successful 30-Gb/s signal transmission of a duobinary message hidden in a chaotic optical carrier over 100-km fiber. Thanks to the duobinary modulation format with high spectral efficiency, the 30-Gb/s signal can be encrypted by a 10-GHz-wide chaotic carrier. A digital signal processing technique can be used to convert duobinary data into binary data on the receiver side. This proposal lowers the requirement for wideband chaos generation and synchronization in high-speed long-distance chaotic optical communications, and fiber dispersion compensation can also be simplified, which has potential to be used in high-speed long-distance secure optical communications...
March 15, 2018: Optics Letters
Shimao Li, Yunhong Ding, Xiaowei Guan, Heyun Tan, Zhichao Nong, Lin Wang, Lin Liu, Lidan Zhou, Chunchuan Yang, Kresten Yvind, Leif Katsuo Oxenløwe, Siyuan Yu, Xinlun Cai
Photonic integrated devices that emit vortex beam carrying orbital angular momentum are becoming key components for multiple applications. Here we propose and demonstrate a high-efficiency vortex beam emitter based on a silicon micro-ring resonator integrated with a metal mirror. Such a compact emitter is capable of generating vortex beams with a high efficiency and small divergence angle. Vector vortex beams of various topological charges are selectively generated by the emitter at different wavelengths with an emission efficiency of up to 37%...
March 15, 2018: Optics Letters
Can Cihan, Abdullah Muti, Isinsu Baylam, Askin Kocabas, Umit Demirbas, Alphan Sennaroglu
We report, to the best of our knowledge, the shortest femtosecond pulses generated from a Kerr-lens mode-locked (KLM) Alexandrite laser operating near 750 nm. The Alexandrite gain medium was pumped with a continuous-wave (cw), 532 nm laser, and the performance of both the short and extended resonators was investigated. The use of an extended cavity eliminated the multi-wavelength spectral instabilities observed during the cw operation of the short cavity. Furthermore, since the repetition rate of the Alexandrite laser was reduced from 107 to 5...
March 15, 2018: Optics Letters
Bing Sun, Fang Fang, Zuxing Zhang, Jing Xu, Lin Zhang
A high-sensitivity and low-temperature fiber-optic magnetic field sensor based on a tapered two-mode fiber (TTMF) sandwiched between two single-mode fibers has been proposed and demonstrated. The section of TTMF has a specifically designed transition region as an efficient tool to filter higher-order modes, where the uniform modal interferometer just involved with LP01 and LP11 modes is achieved. The transmission spectral characteristics and the magnetic response of the proposed sensors have been investigated...
March 15, 2018: Optics Letters
Xiaoyong Huang, Shaoying Wang, Bin Li, Qi Sun, Heng Guo
In this work, we reported on high-brightness Eu3+ -activated Ca3 Lu(AlO)3 (BO3 )4 (CLAB) red-emitting phosphors. Under 397 nm excitation, the CLAB:Eu3+ phosphors showed intense red emissions at around 621 nm with CIE coordinates of (0.657, 0.343). The optimal doping concentration of Eu3+ ions was found to be 30 mol. %, and the CLAB:0.3Eu3+ sample possessed high-color purity of 93% and ultra-high internal quantum efficiency as great as 98.5%. Importantly, the CLAB:0.3Eu3+ also had good thermal stability. Finally, a white-light-emitting diode (WLED) lamp with good color-rendering index was fabricated by using a 365 nm ultraviolet chip and the phosphor blends of CLAB:0...
March 15, 2018: Optics Letters
Amado M Velázquez-Benítez, K Yanín Guerra-Santillán, Raúl Caudillo-Viurquez, J Enrique Antonio-López, Rodrigo Amezcua-Correa, Juan Hernández-Cordero
We demonstrate a simple approach based on a photonic lantern spatial-mode multiplexer and a few-mode fiber for optical and manipulation of multiple microspheres. Selective generation of linearly polarized (LP) fiber modes provides light patterns useful for trapping one or multiple microparticles. Furthermore, rotation of the particles can be achieved by switching between degenerate LP modes, as well as through polarization rotation of the input light. Our results show that emerging fiber optic devices such as photonic lanterns can provide a versatile and compact means for developing optical fiber traps...
March 15, 2018: Optics Letters
Rihui Wu, Adrian Jarabo, Jinli Suo, Feng Dai, Yongdong Zhang, Qionghai Dai, Diego Gutierrez
Introducing polarization into transient imaging improves depth estimation in participating media, by discriminating reflective from scattered light transport and calculating depth from the former component only. Previous works have leveraged this approach under the assumption of uniform polarization properties. However, the orientation and intensity of polarization inside scattering media is nonuniform, both in the spatial and temporal domains. As a result of this simplifying assumption, the accuracy of the estimated depth worsens significantly as the optical thickness of the medium increases...
March 15, 2018: Optics Letters
Lu Cai, Kaikai Du, Yurui Qu, Hao Luo, Meiyan Pan, Min Qiu, Qiang Li
Polar crystals can enable strong light-matter interaction at an infrared regime and provide many practical applications including thermal emission. However, the dynamic control of thermal emission based on polar crystals remains elusive as the lattice vibrations are solely determined by the crystal structure. Here, a nonvolatile tunable midinfrared thermal emitter enabled by a phase-changing film Ge2 Sb2 Te5 on silicon carbide polar crystal is demonstrated. By controlling the state of Ge2 Sb2 Te5 from an amorphous to a crystalline state, the emissivity of the thermal emitter is tuned from a low value to near unity with a maximum change in peak emissivity exceeding 10 dB over the Reststrahlen band of SiC (11...
March 15, 2018: Optics Letters
Franz Beier, Friedrich Möller, Bettina Sattler, Johannes Nold, Andreas Liem, Christian Hupel, Stefan Kuhn, Sigrun Hein, Nicoletta Haarlammert, Thomas Schreiber, Ramona Eberhardt, Andreas Tünnermann
In this contribution we investigate the transversal mode instability behavior of a ytterbium-doped commercial 20/400 fiber and obtain 2.9 kW of output power after optimizing the influencing parameters. In this context, we evaluate the influence of the bend diameter and the pump wavelength within the scope of the absorption length and the length of the fiber. Furthermore, with a newly developed fiber we report on 4.4 kW of single-mode output power at 40 cm bend diameter.
March 15, 2018: Optics Letters
N K Stevenson, C T A Brown, J-M Hopkins, M D Dawson, C Kränkel, A A Lagatsky
We report on the first demonstration, to the best of our knowledge, of a diode-pumped Tm:LuScO3 laser. Efficient and broadly tunable continuous wave operation in the 1973-2141 nm region and femtosecond mode-locking through the use of an ion-implanted InGaAsSb quantum-well-based semiconductor saturable absorber mirror are realized. When mode-locked, near-transform-limited pulses as short as 170 fs were generated at 2093 nm with an average output power of 113 mW and a pulse repetition frequency of 115.2 MHz...
March 15, 2018: Optics Letters
Longchao Yao, Jun Chen, Paul E Sojka, Xuecheng Wu, Kefa Cen
Dynamic stringy objects such as liquid rims and ligaments are frequently observed in important applications such as the multiphase breakup of fuel droplets. We develop a new method based on digital in-line holography to automatically measure complicated stringy objects. A static spring mounted on a rotator is measured to validate the effectiveness and accuracy of the method. The sections are extracted along the skeleton of the spring in a depth-of-field extended image and then sized and located as individual particles using a hybrid method...
March 15, 2018: Optics Letters
Fedor Rudakov, Joseph D Geiser, Peter M Weber
A technique for the spatially resolved and molecule-specific detection of chemical vapors is presented. The chemical specificity arises from a transient absorption spectrum where an ultraviolet (UV) pulse excites the molecule to a Rydberg state, and a near-infrared (NIR) or visible probe pulse records a transient absorption spectrum. By recording the NIR pulse reflected off a random, distant object and measuring the elapsed time between the emission of the UV pulse and the absorption of a counter-propagating NIR pulse, the distance to the absorber is obtained...
March 15, 2018: Optics Letters
Xiao Ming Zhang, Qiang Zhang, Shang Jie Zeng, Zhen Zhen Liu, Jun-Jun Xiao
High-index dielectric nanoantennas have become an emerging branch of optical nanoantennas, essentially due to their low loss. These types of nanoantennas can achieve both forward and backward unidirectional scattering, enabled by electric dipole and magnetic dipole interaction. Here, we show that the scattering directionality can be further enhanced if higher-order moments are properly balanced and reach the generalized Kerker condition at two different wavelengths in an all-dielectric hollow nanodisk. Moreover, putting the nanodisks in an array of transverse configuration can enhance the unidirectionality to be needle-like, with the main lobe angular beam width α<15°...
March 15, 2018: Optics Letters
Haizhou Huang, Jianhong Huang, Yan Ge, Hui Zheng, Wen Weng, Hongchun Wu, Wenxiong Lin
We realize Ho laser operation in a composite Tm/Ho:YAG gain medium for the first time, to the best of our knowledge, which was integrated via diffusion bonding the Tm-doped and Ho-doped crystals into a single bulk structure. A maximum output power around 6 W was obtained with a slope efficiency of 40.1% and conversion efficiency (CE) of 33.6% from the absorbed 785 nm laser diode to 2122 nm Ho laser, which is comparable with CE in 1.9 μm LD pumped Ho lasers. Such a scheme is demonstrated to be another valid way for Ho laser generation here, which is of significance to be adopted in other host media or waveguide structures for an assessable, compact, and efficient Ho laser...
March 15, 2018: Optics Letters
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