| 1. |
- Guo, Shuwei, et al.
(författare)
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Optical surface transformation for reshaping the field intensity distribution
- 2016
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 33:9, s. 1847-1851
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we focus on how to reshape the field intensity distribution on the wavefront of an incident beam and produce special optical beams (e.g., asymmetric Gaussian beams, hollow beams, and zeroth-order Bessel beams) using optical surface transformation (OST). The key design method of this paper is based on OST, which is the extension of transformation optics. Numerical simulations are given to verify the performance of the proposed devices.
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| 2. |
- Hansson, Tobias, 1983, et al.
(författare)
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Frequency comb generation beyond the Lugiato-Lefever equation: multi-stability and super cavity solitons
- 2015
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 32:7, s. 1259-1266
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Tidskriftsartikel (refereegranskat)abstract
- The generation of optical frequency combs in microresonators is considered without resorting to the mean-field approximation. New dynamical regimes are found to appear for high intracavity power that cannot be modeled using the Lugiato-Lefever equation. Using the Ikeda map, we show the existence of multi-valued stationary states and analyze their stability. Period doubled patterns are considered, and a novel type of super cavity soliton associated with the multi-stable states is predicted.
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| 3. |
- Hansson, Tobias, 1983, et al.
(författare)
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Single envelope equation modeling of multi-octave comb arrays in microresonators with quadratic and cubic nonlinearities
- 2016
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 33:6, s. 1207-1215
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Tidskriftsartikel (refereegranskat)abstract
- We numerically study, by means of the single envelope equation, the generation of optical frequency combs ranging from the visible to the mid-infrared spectral regions in resonators with quadratic and cubic nonlinearities. Phase-matched quadratic wave-mixing processes among the comb lines can be activated by low-power continuous wave pumping in the near infrared of a radially poled lithium niobate whispering gallery resonator. We examine both separate and coexisting intracavity doubly resonant second-harmonic generation and parametric oscillation processes and find that modulation instabilities may lead to the formation of coupled comb arrays extending over multiple octaves. In the temporal domain, the frequency combs may correspond to pulse trains or even to a single pulse circulating in the cavity.
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| 4. |
- Helgason, Òskar Bjarki, 1989, et al.
(författare)
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Superchannel engineering of microcombs for optical communications
- 2019
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 36:8, s. 2013-2022
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Tidskriftsartikel (refereegranskat)abstract
- Microresonator frequency combs (microcombs) are a promising technology for generating frequency carriers for wavelength division multiplexing (WDM) systems. Multi-terabit per second WDM coherent transmitters have recently been demonstrated using both dissipative Kerr solitons and mode-locked dark pulses in optical microresonators. These experiments have focused on microcombs designed to cover a large portion of the erbium-doped fiber window. However, the question of optimum bandwidth for microcombs in WDM systems has not been addressed. Here we show that segmenting the bandwidth into smaller microcomb-driven superchannels results in an improvement of power per line. Through numerical simulations we establish a quantitative comparison between dark-pulse and soliton microcombs in WDM systems, including aspects such as conversion efficiency, tolerance to intrinsic cavity loss, and group velocity dispersion engineering. We show that the improvement of minimum line power scales linearly with the number of superchannels for both types of microcombs. This work provides useful guidelines for the design of multi-terabit per second microcomb-based superchannel systems.
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| 5. |
- Johansson, Alexandra C., et al.
(författare)
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Signal line shapes of Fourier-transform cavity-enhanced frequency modulation spectroscopy with optical frequency combs
- 2017
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 34:2, s. 358-365
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Tidskriftsartikel (refereegranskat)abstract
- We present a thorough analysis of the signal line shapes of Fourier-transform-based noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS). We discuss the signal dependence on the ratio of the modulation frequency, f(m), to the molecular linewidth, G. We compare a full model of the signals and a simplified absorption-like analytical model that has high accuracy for low f(m)/G ratios and is much faster to compute. We verify the theory experimentally by measuring and fitting the NICE-OFCS spectra of CO2 at 1575 nm using a system based on an Er: fiber femtosecond laser and a cavity with a finesse of similar to 11000.
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| 6. |
- Maccaferri, Nicolò, Dr. 1988-
(författare)
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Coupling phenomena and collective effects in resonant meta-atoms supporting both plasmonic and (opto-)magnetic functionalities : an overview on properties and applications [Invited]
- 2019
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Ingår i: Journal of the Optical Society of America B. - : Optica Publishing Group. - 0740-3224 .- 1520-8540. ; 36:7, s. E112-E131
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Forskningsöversikt (refereegranskat)abstract
- We review the fundamental aspects and applications of functional magneto-optic and opto-magnetic metamaterials displaying collective and coupling effects on the nanoscale, where the concepts of optics and magnetism merge to produce unconventional phenomena. The use of magnetic materials instead of the usual noble metals allows for an additional degree of freedom for the control of electromagnetic field properties as well as allowing light to interact with the spins of the electrons and to actively manipulate the magnetic properties of such nanomaterials. In this context, we explore the concepts of near-field coupling of plasmon modes in magnetic metamolecules as well as the effect of excitation of surface lattice resonances in magneto-plasmonic crystals. Moreover, we discuss how these coupling effects can be exploited to artificially enhance optical magnetism in plasmonic metamolecules and crystals. Finally, we highlight some of the present challenges and provide a perspective on future directions of the research toward photon-driven fast and efficient nanotechnologies bridging magnetism and optics beyond current limits.
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| 7. |
- Silander, Isak, 1980-, et al.
(författare)
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Model for in-coupling of etalons into signal strengths extracted from spectral line shape fitting and methodology for predicting the optimum scanning range : demonstration of Doppler-broadened, noise-immune, cavity-enhanced optical heterodyne molecular spectroscopy down to 9 × 10−14 cm−1
- 2015
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 32:10, s. 2104-2114
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Tidskriftsartikel (refereegranskat)abstract
- Expressions for the in-coupling of white noise and etalons into fitted signal strengths are derived. These show that the amount of noise picked up is affected by the scanning range. A methodology for finding the optimum scanning range from a single set of measurements has been developed. This was used to estimate the optimum conditions of a noise-immune, cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) setup. The methodology was validated by measurements. This resulted in a spectral noise equivalent absorption per unit length of 2.6 × 10−13 cm−1 Hz−1∕2 and a minimum Allan deviation of 9 × 10−14 cm−1 at 30 s, which are, to our knowledge, the lowest reported for Doppler-broadened NICE-OHMS
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| 8. |
- Sobon, Grzegorz, et al.
(författare)
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Shot-to-shot performance analysis of an all-fiber supercontinuum source pumped at 2000 nm
- 2018
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 36:2, s. A15-A21
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we report an all-fiber supercontinuum source pumped with ultra-short pulses at 1.9–2.0 μm, covering over an octave (1200–2400 nm). We investigated the shot-to-shot stability of the supercontinuum generated in a commercially available highly nonlinear fiber (HNLF) of different lengths, ranging from 5 to 80 cm, by employing the dispersive Fourier transform method. Our study shows that using shorter HNLFs significantly improves the shot-to-shot stability while maintaining the broad spectral coverage. The supercontinuum generated in HNLFs shorter than 10 cm is characterized by excellent stability despite the anomalous-dispersion characteristic of the fiber. The presented source is characterized by exceptional simplicity, showing readiness for outside-of-lab applications.
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| 9. |
- Sun, F., et al.
(författare)
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Waveguide bends by optical surface transformations and optic-null media
- 2018
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 35:4, s. 944-949
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Tidskriftsartikel (refereegranskat)abstract
- We propose what we believe is a novel method to design waveguide bends for metallic waveguides with arbitrary bending angles. The proposed method is based on a new theoretical branch from transformation optics that is referred as to optic surface transformation. Compared with waveguide bends designed by traditional transformation optics, the design process of our method can be made in a graphical way that is very simple and convenient. To realize any waveguide bend designed by the method proposed in this study, one needs only one homogeneous material, i.e., an optic-null medium (even if the bending angles are different for various cases). After some reductions, we find that the optic-null media here can be approximately realized by some anisotropic zero refractive index materials. 2D numerical simulations verify the performance of the designed waveguide bends. The design principle can be extended to the 3D case.
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| 10. |
- Zakomirnyi, Vadim, et al.
(författare)
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Collective lattice resonances in disordered and quasi-random all-dielectric metasurfaces
- 2019
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optics Info Base, Optical Society of America. - 0740-3224 .- 1520-8540. ; 36:7, s. E21-E29
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Tidskriftsartikel (refereegranskat)abstract
- Collective lattice resonances in disordered 2D arrays of spherical Si nanoparticles (NPs) have been thoroughly studied within the framework of the coupled dipole approximation. Three types of defects have been analyzed: positional disorder, size disorder, and quasi-random disorder. We show that the positional disorder strongly suppresses either the electric dipole (ED) or the magnetic dipole (MD) coupling, depending on the axis along which the NPs are shifted. Contrarily, size disorder strongly affects only the MD response, while the ED resonance can be almost intact, depending on the lattice configuration. Finally, random removing of NPs from an ordered 2D lattice reveals a quite surprising result: hybridization of the ED and MD resonances with lattice modes remains observable even in the case of random removing of up to 84% of the NPs from the ordered array. The reported results could be important for rational design and utilization of metasurfaces, solar cells, and other alldielectric photonic devices.
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