Midinfrared (MIR) wavelength conversion based on degenerate four-wave mixing is theoretically investigated in hydrogenated amorphous silicon (a-Si:H) waveguides. The broadband phase mismatch is achieved in the normal ...
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Midinfrared (MIR) wavelength conversion based on degenerate four-wave mixing is theoretically investigated in hydrogenated amorphous silicon (a-Si:H) waveguides. The broadband phase mismatch is achieved in the normal group-velocity dispersion regime. The conversion bandwidth is extended to 900 nm, and conversion efficiency of up to - 14 dB with a pump power of 70 mW in a 2-mm long a-Si:H rib waveguides is obtained. This low-power on-chip wavelength converter will have potential for application in a wide range of MIR nonlinear optic devices. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
Series expansions of unknown fields phi = Sigma phi(n)Z(n) in elongated waveguides are commonly used in acoustics, optics, geophysics, water waves and other applications, in the context of coupled-mode theories (CMTs)...
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Series expansions of unknown fields phi = Sigma phi(n)Z(n) in elongated waveguides are commonly used in acoustics, optics, geophysics, water waves and other applications, in the context of coupled-mode theories (CMTs). The transverse functions Z(n) are determined by solving local Sturm-Liouville problems (reference waveguides). In most cases, the boundary conditions assigned to Z(n) cannot be compatible with the physical boundary conditions of phi, leading to slowly convergent series, and rendering CMTs mildslope approximations. In the present paper, the heuristic approach introduced in Athanassoulis & Belibassakis (Athanassoulis & Belibassakis 1999 J. Fluid Mech. 389, 275-301) is generalized and justified. It is proved that an appropriately enhanced series expansion becomes an exact, rapidly convergent representation of the field phi, valid for any smooth, non-planar boundaries and any smooth enough phi. This series expansion can be differentiated termwise everywhere in the domain, including the boundaries, implementing an exact semi-separation of variables for non-separable domains. The efficiency of the method is illustrated by solving a boundary value problem for the Laplace equation, and computing the corresponding Dirichlet-to-Neumann operator, involved in Hamiltonian equations for nonlinear water waves. The present method provides accurate results with only a few modes for quite general domains. Extensions to general waveguides are also discussed.
We present a method for generating precise, dynamically tunable magnetic potentials that can be described by a polynomial series along the axis of a cold-atom waveguide near the surface of an atom chip. With a single ...
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We present a method for generating precise, dynamically tunable magnetic potentials that can be described by a polynomial series along the axis of a cold-atom waveguide near the surface of an atom chip. With a single chip design consisting of several wire pairs, various axial potentials can be created by changing the ratio of the currents in the wires, including double wells, triple wells, and pure harmonic traps with suppression of higher-order terms. We use this method to design and fabricate a chip with modest experimental requirements. Finally, we use the chip to demonstrate a double-well potential.
Soliton self-frequency shift (SSFS) is an efficient technique of generating broadband tunable femtosecond optical pulses. By using large-mode-area (LMA) waveguides such as photonic-crystal (PC) rods or LMA fibers, SSF...
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Soliton self-frequency shift (SSFS) is an efficient technique of generating broadband tunable femtosecond optical pulses. By using large-mode-area (LMA) waveguides such as photonic-crystal (PC) rods or LMA fibers, SSFS is capable of generating solitons with tens of or even > 100 nJ pulse energy, enabling deep-tissue multiphoton microscopy (MPM) with the unprecedented imaging depth. MPM signals are proportional to the repetition rate of the laser. Here, we demonstrate an efficient technique of enhancing MPM signals in LMA waveguides, through polarization multiplexing, in both a PC rod with no polarization-maintaining (PM) structure and a PM LMA fiber. The collinear output soliton pulses with orthogonal linear polarizations show similar pulse energy, pulse width, and spectrum. We also demonstrate the application of this polarization multiplexing technique to MPM signal enhancement in biological tissues. Compared with single-polarization soliton excitation, excitation with polarization-multiplexed solitons can efficiently boost MPM signals in different modalities of MPM. Published by AIP Publishing.
We report on III-nitride waveguides with c-plane GaN/(Al,Ga)N quantum wells in the strong light-matter coupling regime supporting propagating polaritons. They feature a normal-mode splitting as large as 60 meV at low ...
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We report on III-nitride waveguides with c-plane GaN/(Al,Ga)N quantum wells in the strong light-matter coupling regime supporting propagating polaritons. They feature a normal-mode splitting as large as 60 meV at low temperatures thanks to the large overlap between the optical mode and the active region, a polariton decay length up to 100 μm for photonlike polaritons and a lifetime of 1 to 2 ps, with the latter values being essentially limited by residual absorption occurring in the waveguide. The fully lattice-matched nature of the structure allows for very low disorder and high in-plane homogeneity, which is an important asset for the realization of polaritonic integrated circuits that could support nonlinear polariton wave packets up to room temperature thanks to the large exciton binding energy of 40 meV.
A new combination of porous silicon and polymer optical waveguides is investigated for two different designs of Vernier effect based sensors for the surface detection of Bovine Serum Albumin (BSA) molecules. The hybri...
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A new combination of porous silicon and polymer optical waveguides is investigated for two different designs of Vernier effect based sensors for the surface detection of Bovine Serum Albumin (BSA) molecules. The hybrid structures studied consist of two cascaded micro-resonators for one and a micro-resonator cascaded with a Mach-Zehnder for the other. Because of its high specific surface and bio-compatibility, we use porous silicon to implement the waveguides in the sensing part of the sensor into which BSA molecules are grafted. Polymer waveguides are then used for the reference part of the sensor because of their low optical losses. We consider the optogeometric parameters of both waveguides for single mode propagation. Finally, optimized designs, taking into account standard experimental wavelength shift measurement limitation, are presented for both structures. We demonstrate a theoretical Limit Of Detection (LOD) of 0.019 pg mm(-2) and a sensitivity of 12.5 nm/(pg mm(-2)) with these hybrid sensors. To our knowledge, these values are lower by a factor of 8 for the LOD and higher by a factor of 200 for the sensitivity, as compared to state of the art Vernier effect biosensors. Published by AIP Publishing.
In this work, we show that (real space) curvature in the geometry of curved waveguides with Rashba spin orbit interactions (RSOIs) can lead to out-of-plane spin accumulations. We first derive the RSOI Hamiltonian on a...
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In this work, we show that (real space) curvature in the geometry of curved waveguides with Rashba spin orbit interactions (RSOIs) can lead to out-of-plane spin accumulations. We first derive the RSOI Hamiltonian on arbitrarily curved surfaces. We then analyze the effects of curvature with two distinct methods. We first apply an adiabatic approximation on gently curved, planar waveguides lying flat on the xy plane to show that analogous to the acceleration of the charge carriers by an electric field, the change in the momentum direction of the charge carriers as they move along the waveguide leads to an out-of-plane spin accumulation. We then use the Heisenberg equations of motion to establish the relationships between spin currents and accumulations on non-planar waveguides. These relations predict the existence of out-of-plane spin accumulation on asymmetrically curved, non-planar waveguides. We finally solve for the eigenstates on such waveguides numerically and present numerical results to verify our analytic predictions. Published by AIP Publishing.
Proof is given for the inequality between the group velocity and the energy velocity of plasmonic waves on metal-insulator waveguides considering the Bohm potential. Published by AIP Publishing.
Proof is given for the inequality between the group velocity and the energy velocity of plasmonic waves on metal-insulator waveguides considering the Bohm potential. Published by AIP Publishing.
A simple experimental method for determining the number of modes in planar dielectric multimode waveguides, and the effective index difference of these modes, is presented. Applying a thin, dye-doped polymer cladding,...
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A simple experimental method for determining the number of modes in planar dielectric multimode waveguides, and the effective index difference of these modes, is presented. Applying a thin, dye-doped polymer cladding, the fluorescence excited by multiple modes propagating in a silicon nitride slab waveguide is imaged to extract information. Interference between the modes produces a structured intensity profile along the waveguide which is constant in time. The spatial frequencies of this intensity profile are directly linked to the propagation constants of the underlying modes. Through a discrete Fourier transform, the modes' effective index differences are found and compare well with analytically calculated values. Furthermore, the amplitudes in the Fourier transform are directly related to the power in each mode. Comparing the amplitudes of the Fourier components as a function of propagation distance, an estimate of the propagation losses of the individual modes relative to one another is made. The method discussed could be applied to analysing mode behaviour in integrated photonic devices, most notably in modedivision multiplexing.
A silicon device to simplify the coupling of multiple single-mode fibers to embedded single-mode waveguides has been developed. The silicon device features alignment structures that enable a passive alignment of fiber...
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A silicon device to simplify the coupling of multiple single-mode fibers to embedded single-mode waveguides has been developed. The silicon device features alignment structures that enable a passive alignment of fibers to integrated waveguides. For passive alignment, precisely machined V-grooves on a silicon device are used and the planar lightwave circuit board features high-precision structures acting as a mechanical stop. The approach has been tested for up to eight fiber-to-waveguide connections. The alignment approach, the design, and the fabrication of the silicon device as well as the assembly process are presented. The characterization of the fiber-to-waveguide link reveals total coupling losses of (0.45 +/- 0.20 dB) per coupling interface, which is significantly lower than the values reported in earlier works. Subsequent climate tests reveal that the coupling losses remain stable during thermal cycling but increases significantly during an 85 degrees C/85 Rh-test. All applied fabrication and bonding steps have been performed using standard MOEMS fabrication and packaging processes. (C) The Authors.
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