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Optics Letters | Page 2

Markus Nyman, Somendu Maurya, Matti Kaivola, Andriy Shevchenko
Wave retarders, including quarter- and half-wave plates, are used in many optical systems for polarization conversion. They are usually realized with anisotropic crystalline materials. However, much thinner and possibly also less expensive wave plates can be made of micro- and nanostructures. We present a new way to create thin-film optical retarders based on a highly birefringent metamaterial. The wave plate is capable of low-loss, broadband operation, which we verify both numerically and experimentally. Owing to the remarkable simplicity of our design, the wave plates operating on the proposed principle can meet the requirements of large-scale production and find widespread application in optics and photonics...
June 15, 2019: Optics Letters
Huicong Zhang, Manna Chen, Ling Yang, Bo Tian, Chengjie Chen, Qi Guo, Qian Shou, Wei Hu
We report, to the best of our knowledge, the first experimental observation of higher-charge vortex solitons and vector vortex solitons in lead glass with strongly thermal nonlocal nonlinearity. A higher-charge vortex soliton with a topological charge of l=4 and a vector vortex soliton consisting of two orthogonally polarized vortex components, with charges l1 =1 and l2 =4, were observed at several times of diffraction length. We show that the ring profiles and the carried topological charges of the two incoherently coupled vortex components can be preserved...
June 15, 2019: Optics Letters
Jacopo Rubens Negri, Federico Pirzio, Antonio Agnesi
A passively Q-switched Nd:YAG undirectional ring laser with external feedback is reported. The laser generates 50 ns single-axial-mode pulses up to 6 kHz, with energy 34 μJ, M2 <1.05, and pulse jitter <50  ns rms, which is quite remarkable for this class of devices. Jitter was effectively minimized by using relatively high-peak-power pump pulses of 10 W, in agreement with a model considering both pump fluctuations and spontaneous emission noise. This represents an improvement by a factor of 8 with respect to a similar laser device we recently reported...
June 15, 2019: Optics Letters
Clément Maës, Grégory Vincent, Fernando González-Posada Flores, Laurent Cerutti, Riad Haïdar, Thierry Taliercio
We present a theoretical and experimental study of guided-mode resonant (GMR) spectral filters made of III-V semiconductors and operating in the long-wave infrared (LWIR) wavelength range. In the scope of the colorization of infrared photodetectors, we used materials fully compatible with the epitaxial growth of Type 2 super lattice LWIR photodetectors: heavily n-doped InAsSb for the grating and GaSb for the waveguide of the GMR resonator.
June 15, 2019: Optics Letters
Hossein Taheri, Andrey B Matsko
Solitons, ubiquitous in nonlinear sciences, are wavepackets which maintain their characteristic shape upon propagation. In optics, they have been observed and extensively studied in optical fibers. The spontaneous generation of a dissipative Kerr soliton (DKS) train in an optical microresonator pumped with continuous wave (CW) coherent light has placed solitons at the heart of optical frequency comb research in recent years. The commonly observed soliton has a "sech"-shaped envelope resulting from resonator cubic nonlinearity balanced by its quadratic anomalous group velocity dispersion (GVD)...
June 15, 2019: Optics Letters
Prateek R Srivastava, Ying-Ju Lucy Chu, Grover A Swartzlander
A passively stable laser-driven lightsail is described, which makes use of a spatially variant "bi-grating" sail with a mass (payload) attached to a boom (patent pending). A two-dimensional analytical model of the system, a linear stability analysis, and numerical solutions of the equations of motion are reported. The acceleration of the light sail along the beam path is found to depend on the grating parameters. We identify stability conditions that depend on the grating design, beam parameters, and boom length...
June 15, 2019: Optics Letters
Aurélien Coillet, Zhen Qi, Irina V Balakireva, Guoping Lin, Curtis R Menyuk, Yanne K Chembo
We demonstrate that extended dissipative structures in Kerr-nonlinear whispering-gallery mode resonators undergo a spatiotemporal instability, as the pumping parameters are varied. We show that the dynamics of the patterns beyond this bifurcation yield specific Kerr comb and sub-comb spectra that can be subjected to a phase of frequency-locking when optimal conditions are met. Our numerical results are found to be in agreement with experimental measurements.
June 15, 2019: Optics Letters
Caroline L Anyi, Robert J Thirkettle, Graeme J MacDonald, K Ulrich Schreiber, Jon-Paul R Wells
We report the development and initial operation of a 6.4 meter perimeter laser gyroscope employing the 543.3 nm, 3s2 →2p10 transition of neon. Employing fused silica based supermirrors yielding a cavity Q of 3.9×1011 and an inferred lock in threshold below 1 μHz, the gyroscope unlocked on the bias provided by Earth rotation alone with a measured Sagnac frequency of approximately 133 Hz, which is 16% larger than that of the 632.8 nm transition.
June 15, 2019: Optics Letters
Xiao-Bo Hu, Bo Zhao, Zhi-Han Zhu, Wei Gao, Carmelo Rosales-Guzmán
Laser remote sensing represents a powerful tool that enables the accurate measurement of the speed of moving targets. Crucially, most sensing techniques are two-dimensional (2D) and only enable direct determination of the speed along the line of sight. Here we put forward a novel three-dimensional technique that enables the direct and simultaneous measurement of both the longitudinal and angular speed of cooperative targets. This technique is based on the use of complex vector light beams, whose polarization and spatial degree of freedom are coupled in a non-separable way...
June 15, 2019: Optics Letters
Anne-Lise Viotti, Fredrik Laurell, Andrius Zukauskas, Carlota Canalias, Valdas Pasiskevicius
The frequency modulation transfer property of a backward-wave optical parametric oscillator (BWOPO) is investigated in the context of near-IR pulse compression. The maximum transferrable bandwidth from the pump to the forward wave in a BWOPO is determined by the group dispersion mismatch. In comparison, the third-order phase introduced in a single-grating compressor setup is more detrimental to achieve optimum compression of the BWOPO forward wave. Nevertheless, we demonstrate a 220 GHz bandwidth transfer from 800 nm to 1...
June 15, 2019: Optics Letters
Tengfei Hao, Jian Tang, Nuannuan Shi, Wei Li, Ninghua Zhu, Ming Li
We propose and experimentally demonstrate a photonic-assisted approach to microwave frequency measurement based on frequency-to-time mapping using a Fourier domain mode-locked optoelectronic oscillator (FDML OEO) operating around oscillation threshold. A relationship between the frequency of the unknown input microwave signals and the time difference of the output pulses is established with the help of the frequency scanning capability of the FDML OEO and, thus, can be used for microwave frequency measurement...
June 15, 2019: Optics Letters
Yueyang Chen, James Whitehead, Albert Ryou, Jiajiu Zheng, Peipeng Xu, Taylor Fryett, Arka Majumdar
Tunable silicon nitride nanophotonic resonators are a critical building block for integrated photonic systems in the visible wavelength range. We experimentally demonstrate a thermally tunable polymer-embedded silicon nitride nanobeam cavity with a tuning efficiency of 44 pm/°C and 0.13 nm/mW in the near-visible wavelength range. The large tuning efficiency comes from the high thermo-optic coefficient of the SU-8 polymer and the "air-mode" cavity design, where a large portion of the cavity field is confined inside the polymer region...
June 15, 2019: Optics Letters
Geoffrey M Diederich, Mark E Siemens
Establishing the correct phase in multidimensional coherent spectroscopy (MDCS) experiments is critical because the interpretation of quantum pathways is based on the phase of their associated spectral features but is not trivial because the phase introduced by experimental conditions can contaminate the signal. Most phase-modulated MDCS (PM-MDCS) experiments study molecular systems for which the spectra can be phased to produce absorptive lineshapes, but this assumption of absorptive lineshapes can break down in more complicated systems...
June 15, 2019: Optics Letters
Na Liu, Jia Zhao, Liuge Du, Chuanning Niu, Xiao Lin, Zuojia Wang, Xun Li
Enhancing nonreciprocal light-matter interaction at subwavelength scales has attracted enormous attention due to high demand for compact optical isolators. Here, we propose a significant enhancement of the magneto-optical effect in low-biased gyromagnetic media via photonic doping. Magnetic particles immersed in a gyrotropy-near-zero medium act as dopants that largely modify the macroscopic gyromagnetic effects as well as the gyroelectric ones. Around the resonance frequency, the gyromagnetic activity is largely increased and even exceeds unity, thus providing a photonic band in which the wavenumber of one circularly polarized wave becomes purely imaginary...
June 15, 2019: Optics Letters
Shi Chen, Jian Wang
We present two kinds of fully degeneracy-lifted solid-core photonic crystal multi-mode fibers aiming at multiple-input multiple-output-free direct fiber vector eigenmode multiplexing transmission. One of the target fiber structures is able to support 52 fully separated eigenmodes with effective index difference above 1.37×10-4 and confinement loss below 3.28×10-5   dB/km over the whole C+Lband (1530-1625 nm). Specifically, it is suggested that >10-4 effective index separation is sufficient to possess polarization-maintaining properties, while for short-reach stable mode-division multiplexing transmission, the effective index difference >10-3 is highly desired...
June 15, 2019: Optics Letters
Dmitry N Makarov, Marat K Eseev, Ksenya A Makarova
The interaction of atomic systems with high-power ultrashort electromagnetic field pulses (USPs) is currently the subject of many theoretical and experimental studies. However, a wave function has yet to be developed for the atomic electron located in such fields, including relativistic fields. In this Letter, an equation is obtained that is similar to the Schrödinger equation for the fields under consideration, but which takes into the account relativistic effects in powerful spatially inhomogeneous fields of USPs...
June 15, 2019: Optics Letters
Tomoyoshi Shimobaba, David Blinder, Michal Makowski, Peter Schelkens, Yota Yamamoto, Ikuo Hoshi, Takashi Nishitsuji, Yutaka Endo, Takashi Kakue, Tomoyoshi Ito
This Letter aims to propose a dynamic-range compression and decompression scheme for digital holograms that uses a deep neural network (DNN). The proposed scheme uses simple thresholding to compress the dynamic range of holograms with 8-bit gradation to binary holograms. Although this can decrease the amount of data by one-eighth, the binarization strongly degrades the image quality of the reconstructed images. The proposed scheme uses a DNN to predict the original gradation holograms from the binary holograms, and the error-diffusion algorithm of the binarization process contributes significantly to training the DNN...
June 15, 2019: Optics Letters
P H Tuan, Y T Yu, K F Huang, Y F Chen
The formation of thermally detuned transverse patterns of a broad-area square-aperture vertical-cavity surface-emitting laser (VCSEL) via cryogenic cooling is explored. It is found that the transverse wave vector gradually rotates from the horizontal or vertical direction to the diagonal direction of the square boundary as the transverse mode order increases. A model based on the quantum billiards with a finite potential well is developed to emulate the transition behavior of lasing modes. Combining the effective modal gain analysis with the response wave function of driven finite potential billiards, all experimental lasing patterns under different operation temperatures are well reconstructed...
June 15, 2019: Optics Letters
Jian Wei You, Nicolae C Panoiu
We demonstrate that the effective 3rd-order nonlinear susceptibility of a graphene sheet can be enhanced by more than 2 orders of magnitude by patterning it into a graphene metasurface. In addition, to gain deeper physical insights into this phenomenon, we introduce a versatile homogenization method, which is subsequently used to characterize quantitatively this nonlinearity enhancement effect by calculating the effective linear and nonlinear susceptibility of graphene metasurfaces. The accuracy of the proposed homogenization method is demonstrated by comparing its predictions to those obtained from the Kramers-Kronig relations...
June 15, 2019: Optics Letters
Honggang Gu, Xiuguo Chen, Hao Jiang, Yating Shi, Shiyuan Liu
We propose a universal method for optimal design of a wide field-of-view (FOV) angle linear retarder with an ultra-flat retardance response based on paired positive/negative birefringent plates. The mechanism and rules for the FOV effect compensation are revealed to determine the structure of the proposed retarder by introducing the partial derivative of refractive index with respect to the incident angle. A concrete example based on quartz/sapphire plates is designed and manufactured as a proof-of-concept of the proposed method...
June 15, 2019: Optics Letters
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