Planar waveguides are built up (around 300 K) in lithium iodate by means of proton implantation. The waveguide properties are investigated by a prism coupling technique (m-lines spectroscopy). Both TE and TM modes are...
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Planar waveguides are built up (around 300 K) in lithium iodate by means of proton implantation. The waveguide properties are investigated by a prism coupling technique (m-lines spectroscopy). Both TE and TM modes are used to investigate the ordinary and extraordinary indices. The reconstructed index profiles obtained with inverse WKB method, are compared to the ion concentration profile as determined by simulation (TRIM). All the measured effective index values are smaller than these of the bulk indice. Moreover, the optical barrier is relevant to a maximum index change of about 0.03.
The system of the eigenmodes propagating along an anisotropic fibre is constructed by the S-operator method. The fields of the radiation modes are shown to be unbounded at infinity in cross-section. For these modes th...
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The system of the eigenmodes propagating along an anisotropic fibre is constructed by the S-operator method. The fields of the radiation modes are shown to be unbounded at infinity in cross-section. For these modes the orthogonality relations are derived with the help of regularisation of divergent integrals. The normalising factor is demonstrated to be expressed in terms of the eigenvectors of the S-operator. The results obtained are applied to an excitation problem. The structure of the far-zone fields is analysed.
Signal amplitudes of pulses of ultrasound over the frequency range 1.0-5.0 MHz propagating along a variety of polycrystalline metal wires of diameter 0.5 mm and 1.0 mm are compared. Polycrystalline metal wires used we...
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Signal amplitudes of pulses of ultrasound over the frequency range 1.0-5.0 MHz propagating along a variety of polycrystalline metal wires of diameter 0.5 mm and 1.0 mm are compared. Polycrystalline metal wires used were stainless steel (type 302), aluminium, brass, copper, zinc, iron, nickel, nickel chromium, monel, kovar and invar. It was found that attenuation of ultrasound was greatest in those wires characterized by a higher degree of anisotropy. It was also found that the greater the degree of anisotropy of the polycrystalline metal wires, the poorer the agreement between theoretical and experimental results of group velocities of modes. Of all the wires investigated, stainless steel generally gave rise to the lowest insertion loss over most frequencies.
The paper presents a variational formulation for a junction between collinear rectangular and circular waveguides coupled through a rectangular slot in the common transverse wall. The equivalent circuit, taking the ef...
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The paper presents a variational formulation for a junction between collinear rectangular and circular waveguides coupled through a rectangular slot in the common transverse wall. The equivalent circuit, taking the effect of wall thickness into account, is determined. Numerical results on admittance loading, the reflection coefficient and the input VSWR are evaluated, and a comparison between the theoretical and experimental results on the variation of the VSWR with frequency is presented.
Scaling rules implicit in the model for field assisted ion diffusion into glass have been experimentally observed in planar guides made by the diffusion of silver ions from silver films into soda-lime glass. These sca...
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Scaling rules implicit in the model for field assisted ion diffusion into glass have been experimentally observed in planar guides made by the diffusion of silver ions from silver films into soda-lime glass. These scaling rules are observed despite the relatively poor agreement between the refractive index profile and calculations.
waveguides written in semiconductor microcrystalline-doped glasses using the ion-exchange method have been optically encoded for second harmonic generation of Nd:YAG radiation.
waveguides written in semiconductor microcrystalline-doped glasses using the ion-exchange method have been optically encoded for second harmonic generation of Nd:YAG radiation.
Reverse exchange has been used to bury proton exchanged LiNbO3 waveguides. Following initial exchange and annealing steps, which define the guides, a second exchange reintroduces lithium, thus lowering the extraordina...
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Reverse exchange has been used to bury proton exchanged LiNbO3 waveguides. Following initial exchange and annealing steps, which define the guides, a second exchange reintroduces lithium, thus lowering the extraordinary refractive index at the surface. The buried guides have little optical power at the surface and a more nearly symmetrical mode than unburied guides, resulting in lower propagation losses and better fibre-to-guide coupling.
Four-layer waveguided structures exhibiting acceptable losses have been realized using spin-coated samples of poly(3-alkylthiophene) from FeCl3. Particular attention has been devoted to the molecular-weight range and ...
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Four-layer waveguided structures exhibiting acceptable losses have been realized using spin-coated samples of poly(3-alkylthiophene) from FeCl3. Particular attention has been devoted to the molecular-weight range and crystallite dimensions to minimize the scattering losses and to increase the birefringence. Time-resolved bleaching decay measurements gave strong off-resonance signals (lambda range 1300-1500 nm), indicating interesting chi((3)) values.
A Y-junction digital optical switch based on InP/GaInAsP has been realised and operated using either carrier injection or carrier depletion. The switch functions with both TE and TM polarised light. In the case of cur...
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A Y-junction digital optical switch based on InP/GaInAsP has been realised and operated using either carrier injection or carrier depletion. The switch functions with both TE and TM polarised light. In the case of current injection, 30mA is enough to obtain a crosstalk up to 20 dB for TM polarisation and 10 dB for TE polarisation.
Optical switching of femtosecond pulses is achieved at 1-5 mum using a refractive nonlinearity in a GaAs/AlGaAs MQW waveguide birefringent gate. The switching mechanism is demonstrated with a maximum throughput of 54%...
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Optical switching of femtosecond pulses is achieved at 1-5 mum using a refractive nonlinearity in a GaAs/AlGaAs MQW waveguide birefringent gate. The switching mechanism is demonstrated with a maximum throughput of 54% of the available transmitted power corresponding to an effective phase shift between polarisations of 90-degrees. Normalised transmission is increased by a factor of 44 by increasing the peak coupled pump power from 1 to 330 W.
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