Electro-optic modulation using a low-loss PZT-on-SiN waveguide platform is demonstrated. Using a ring resonator a V pi L pi of approximate to 1 Vcm is demonstrated. Small-signal measurements have demonstrated a bandwi...
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(纸本)9781943580279
Electro-optic modulation using a low-loss PZT-on-SiN waveguide platform is demonstrated. Using a ring resonator a V pi L pi of approximate to 1 Vcm is demonstrated. Small-signal measurements have demonstrated a bandwidth surpassing 25 GHz.
Transformation optics has revolutionized our approach to material design in several scientific disciplines by determining the material properties that implement the desired effects of a coordinate transformation. Unfo...
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Transformation optics has revolutionized our approach to material design in several scientific disciplines by determining the material properties that implement the desired effects of a coordinate transformation. Unfortunately, the performance of several coordinate-based devices, such as beam splitters and invisibility cloaks, suffers from the necessary implementation of singularities with extreme material parameters. Here, we make use of transformation optics to eliminate these singularities in an isotropic way for the improvement of coordinate-based metamaterial waveguides. In particular, singularities that lead to vanishing material properties are softened with a global rescaling of the coordinates, while singular terms that lead to infinite material properties are strategically replaced by well-behaved curve factors. Detailed full-wave simulations confirm that the resulting waveguide devices are as efficient as their singular counterparts despite the fact that they consist of materials with much more moderate optical properties.
Purpose: The design of RF coils for MRI transmit becomes increasingly challenging at high frequencies required for MRI at 7T and above. Our goal is to show a proof of principle of a new type of transmit coil for highe...
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Purpose: The design of RF coils for MRI transmit becomes increasingly challenging at high frequencies required for MRI at 7T and above. Our goal is to show a proof of principle of a new type of transmit coil for higher field strengths. Method: We demonstrate an alternative transmit coil design based on dielectric waveguide principles which transfers energy via evanescent wave coupling. The operating principles and conditions are explored by simulations. The waveguide is applied for in vivo imaging at 7T. Results: The waveguide can be an efficient transmit coil when four conditions are fulfilled: (1) the waveguide should be operated just above the cutoff frequency of the lowest order transverse electric mode, (2) the waveguide should not operate at a frequency where the wavelength fits an integer number of times in the waveguide length and standing wave patterns become very prominent, (3) for homogeneous excitation, the waveguide should be bent around the object, and (4) there should be an air gap between the waveguide and the object. Conclusions: By choosing the dielectric and the dimensions adequately, the dielectric waveguide couples the magnetic field efficiently into the body. The waveguide can be redesigned for higher frequencies by simple adaptations and may be a promising transmit alternative. (C) 2015 Wiley Periodicals, Inc.
We present a numerical analysis of surface plasmon dispersion and the nonlinear nature of wave propagation on different smooth waveguides with lossy noble metal films. We also analyze the effective parameters that can...
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We present a numerical analysis of surface plasmon dispersion and the nonlinear nature of wave propagation on different smooth waveguides with lossy noble metal films. We also analyze the effective parameters that can affect the dispersion behavior of a thin dielectric slab waveguide embedded in a symmetric metal film. Three kinds of metal (silver, gold, and copper) with Johnson-Christy constants have been utilized in waveguides. Four kinds of dielectric material (air, Teflon, FR-4, and silicon) have been employed in the insulator layer of the metal-insulatormetal waveguide. The dispersion curve of the metal-insulator-metal waveguide with different metal and dielectric arrangements has been studied numerically. By multi-nominal fitting of dispersion curves, we have derived the nonlinear properties of Gaussian (chirped) wave propagation, dispersion length, and pulse broadening through a three-layer plasmonic waveguide. A comparison of three-layered plasmonic waveguides with different guiding layers has been accomplished. Simulation results have shown that dispersion curves with a larger peak and a quasi-bound mode cause the Gaussian waves to be dispersed and broadened during longer traveling distances. The achieved results serve an impressive function in the design of optical switches and delay lines. (C) 2017 Optical Society of America
We present an approach and a theoretical framework for generating high-order exceptional points of degeneracy (EPDs) in photonic structures based on periodic coupled resonator optical waveguides (CROWs). Such EPDs inv...
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We present an approach and a theoretical framework for generating high-order exceptional points of degeneracy (EPDs) in photonic structures based on periodic coupled resonator optical waveguides (CROWs). Such EPDs involve the coalescence of Floquet-Bloch eigenwaves in CROWs, without the presence of gain and loss, which contrasts with the parity-time symmetry required to develop exceptional points based on gain and loss balance. The EPDs arise here by introducing symmetry breaking in a conventional chain of coupled resonators through periodic coupling to an adjacent uniform optical waveguide, which leads to unique modal characteristics that cannot be realized in conventional CROWs. Such remarkable characteristics include high quality factors (Q factors) and strong field enhancement, even without any mirrors at the two ends of a cavity. We show for the first time the capability of CROWs to exhibit EPDs of various orders, including the degenerate band edge (DBE) and the stationary inflection point. The proposed CROW of finite length shows an enhanced quality factor when operating near the DBE, and the Q factor exhibits an unconventional scaling with the CROW's length. We develop the theory of EPDs in such unconventional CROW using coupled-wave equations, and we derive an analytical expression for the dispersion relation. The proposed unconventional CROW concepts have various potential applications including Q switching, nonlinear devices, lasers, and extremely sensitive sensors.
We theoretically demonstrate optical trapping using a silicon nitride (Si3N4) trench waveguide on which bow-tie plasmonic nanoantennas are employed for enhancing optical forces. The electric field tailing away from th...
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We theoretically demonstrate optical trapping using a silicon nitride (Si3N4) trench waveguide on which bow-tie plasmonic nanoantennas are employed for enhancing optical forces. The electric field tailing away from the waveguide is transformed and then enhanced by the plasmonic nanoantennas deposited on the waveguide surface. We show that, with gold bow-tie nanoantennas, the waveguide system exhibits outstanding trapping capability on a 10 nm radius polystyrene nanoparticle, due to a 60-fold electric field enhancement in the proximity of the nanoantenna gap. This enhancement causes a boost of the optical trapping force by 3 orders of magnitude. The gradient force in the vertical direction is also calculated semi-analytically by using a dipole approximation of a scattering polystyrene nanosphere, and the analytical solution well matches the full-wave simulations. Mode polarization effects are discussed in this paper as a way to switch trapping. These investigations indicate that the patterned Si3N4 trench waveguide is suitable for optical trapping and nanoparticle sensing applications. (C) 2016 Optical Society of America
In this paper we report the design and experimental realisation of a novel refractive index sensor based on coupling between three nanoscale stripe waveguides. The sensor is highly compact and designed to operate at a...
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In this paper we report the design and experimental realisation of a novel refractive index sensor based on coupling between three nanoscale stripe waveguides. The sensor is highly compact and designed to operate at a single wavelength. We demonstrate that the sensor exhibits linear response with a resolution of 6 x 10(-4) RIU (refractive index unit) for a change in relative output intensity of 1%. Authors expect that the outcome of this paper will prove beneficial in highly compact, label-free and highly sensitive refractive index analysis.
This work reports on the passively Q-switched waveguide laser system based on Nd:YAG crystal and MoS2 satuable absorber. A depressed cladding waveguide with circular cross-sectional geometry has been produced in Nd: Y...
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This work reports on the passively Q-switched waveguide laser system based on Nd:YAG crystal and MoS2 satuable absorber. A depressed cladding waveguide with circular cross-sectional geometry has been produced in Nd: YAG crystal by direct femtosecond laser writing at low-repetition rate. The confocal microscopic investigation of the structure reveals the well-preserved microphotoluminescence features in the waveguide core. With chemical-vapor-deposition (CVD) MoS2 membrane as satuable absorber, the passive Q-switching of the Nd: YAG waveguide system has been achieved under optical pump, reaching maximum average output power of 85.2 mW, corresponding to single-pulse energy of 112 nJ, at wavelength of 1064 nm. The repetition rate of the pulsed waveguide laser system is tunable from 0.51 to 1.10 MHz, and the obtained minimum pulse duration is 203 ns. (C) 2016 Optical Society of America
Optical autocorrelation accuracy was for the first time analyzed for the silicon waveguide based autocorrelators utilizing two-photon absorption (TPA) under various short pulse conditions by numerical simulation. As f...
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Optical autocorrelation accuracy was for the first time analyzed for the silicon waveguide based autocorrelators utilizing two-photon absorption (TPA) under various short pulse conditions by numerical simulation. As for autocorrelation operation in the sub-mu m silicon p-i-n rib waveguides on the 220 nm SOI (silicon on insulator) wafers, the autocorrelation error of pulse width measurement gradually increases with the increase of the peak power for both Gaussian and hyperbolic secant pulses due to the influence of free-carrier absorption (FCA). For the same pulse type, the relative error is independent of the input pulse width;however different pulse type has different peak power dependency of the accuracy. It was verified that this thin rib waveguide has a TPA responsivity > 60 times higher than the thick rib waveguides and the correct pulse width can be measured with a < 1% relative error for characterizing ps/sub-ps short pulses of sub-watt peak powers by utilizing the silicon wire p-i-n waveguides as the autocorrelator detector. (C) 2016 Optical Society of America
Deep subwavelength plasmonic graphene nanoribbon waveguides for telecommunication frequencies are proposed. The mode properties of graphene nanoribbon waveguides with varied chemical potential are numerically investig...
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Deep subwavelength plasmonic graphene nanoribbon waveguides for telecommunication frequencies are proposed. The mode properties of graphene nanoribbon waveguides with varied chemical potential are numerically investigated in terms of the effective indices and the propagation length of the plasmonic modes. A refractive index as high as 4980 is obtained on the plasmonic mode along the nanoribbon waveguide with a width of 3 nm at a frequency of 190 THz, and the normalized mode area on the scale of 10(-8)(1/lambda(0))(2). An embedded graphene nanoribbon waveguide was also proposed and it is that the optical characteristic can be tuned by adjusting the chemical potential of graphene. The proposed structure can be a fundamental component of the future integrated plasmonic circuit system. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)
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