Showing papers on "Guided wave testing published in 1984"

Observation of intensity-dependent guided waves

Abstract: We have observed an intensity-dependent hysteresis in the transmission of guided waves through a thin-film waveguide with a cladding characterized by an intensity-dependent refractive index. Good agreement with theory was obtained.

Waveguide grating lenses for optical couplers.

Abstract: New waveguide grating lenses for coupling a guided wave to a spherical wave, focusing in the air, have been designed. The lenses have the advantages. of high efficiency and high practicability for fabrication. Chirped and curved grating lenses were fabricated on PMMA waveguides by an electron beam exposure system.

Optical bistability on reflection with an InSb étalon controlled by a guided wave.

Abstract: We report experimental results on optical bistability using an InSb etalon gold coated on one face, at 80 K and 5.59-μm wavelength. The bistability, observed on reflection, was controlled by a beam coupled through the edge of the etalon. The geometry lends itself to the possibility of addressing a large number of individual spots, all of which are controlled by the same guided beam.

Guided wave optical frequency shifter

Abstract: This invention is a frequency shifter for receiving an optical carrier signal input and producing an output including a sideband that is shifted in frequency from the carrier. The frequency shifter includes an optical waveguide formed in a substrate of an electro-optically active material such as lithium niobate. A plurality of electrodes formed on the substrate cooperate with a signal generator to apply two perpendicular electric fields to the optical waveguide. The resultant of the two fields is a rotating electric field which produces a rotating birefringence in the optical waveguide. The rotating birefringence acts as a rotating wave plate, which shifts the frequency of optical signals input to the optical waveguide. The wave plate is preferably a half wave plate, which converts all of the input optical energy into the sideband.

Degenerate four-wave mixing with surface guided waves

Abstract: The theory of degenerate four-wave mixing with surface guided waves is developed and used to derive expressions for the non-linear cross sections. The relative merits of using planar thin film dielectric waveguides versus surface plasmons guided by metal surfaces are discussed, with specific numerical examples based on PTS and InSb.

Anomalous nonlinear guided wave cut‐off phenomena

Abstract: We show that mode cutoff can occur at finite powers for waves guided by a thin‐film waveguide bounded by one or two media characterized by a defocusing nonlinearity. This phenomenon produced optical limiting action.

Evolution of transverse-magnetic surface and leaky waves guided by an asymmetric layer configuration

Abstract: The evolution of surface and leaky waves as a function of frequency is examined for perpendicular polarization [transverse-electric (TEN) modes] in configurations consisting of a dielectric slab bounded by media having different refractive indices. We find that, at any frequency, these waves occur in sets of four types for all higher-order (N > 1) mode numbers. The characteristics and the field patterns of these wave types are discussed, and the special behavior of the first two (N = 0, 1) modes is described in detail.

Transfer efficiencies in guided wave electrooptic filters/mode converters

Abstract: The influence of a spatially nonuniform electric field on the polarization Conversion efficiency of single- and multimode guided wave electrooptic filters is analyzed quantitatively, using coupled-mode theory. A single-mode graded-index surface waveguide filter is capable of essentially 100-percent transfer efficiency, with overlap integrals of field and a single TE, TM mode pair approaching 0.6 in Ti: LiNbO 3 . The thicker multi-mode slab waveguides require that spatial periods of applied field be considerably greater than the guide thickness to achieve high transfer efficiency, though never quite 100 percent; The best performance also requires focused coupling into the lowest order mode only. Experimental results with a LiTaO 3 slab waveguide filter show reasonable agreement with a multiple-coupled-mode solution.

Characterization method of birefringent films by guided optical waves.

Abstract: A method is presented that gives the thickness, both the ordinary and the extraordinary refractive indices, and the angle between the c axis and the surface of a thin dielectric film by measuring the effective index of TE and TM propagating modes.

Analysis of open optical and microwave guides of arbitrary transverse permittivity profiles

Abstract: A full vector H field finite element formulation has been developed for the analysis of a wide range of uniform guided wave problems. It deals with microwave or optical structures where the permittivity has arbitrary variation in the transverse cross section. The permittivity can have a tensor of arbitrary anisotropy, limited only to being loss-free. Infinite elements have been introduced to represent well the fields in an open type of waveguide. A matrix algorithm is used which takes complete advantage of the matrices' sparsity. Computed results are illustrated with optical channel and rib guide, image guide, and waveguide containing a skew uniaxial dielectric.

Guided-Wave Characteristics And Optical Damage In LiNb0 3 Waveguides

Abstract: High power optical performances of Ti-indiffused and ion-exchanged waveguides were investigated and discussed. It was experimentally confirmed that Ti-indiffused waveguide suffered a serious optical damage at the output power density less than 0.1 mW/mm at A = 0.6328 pm. For x-propagating guided waves in y-cut crystal, the throughput decay time, by which we could characterize the dependences of optical damage, was revealed to be inversely propor-tional to square of initial guided power, P2, for TE modes, and to P3 for TM modes, and also confirmed to increase with an exponential function of wavelength λ. No optical damage was found for z-propagating guided waves. Proton-exchanged waveguides exhibited to have a good damage resistance. Their surface acoustic wave(SAW) performances, however, were found to be degraded; an IDT's insertion loss of 45 dB was measured, which was much larger than 13 - 14 dB available for Ti-indiffused waveguides. According to the experimental results of infrared absorption spectra, we speculate that the deterioration of SAW performances is attributed to the formation of a HNbO3 phase. A preliminary study using electron spin resonance(ESR) at 77 K provided us a good evidence of the close relation between impurities such as iron and free electrons in the crystal under UV light irradiation.

Higher Order Characteristics of Waves on a Sinusoidally Modulated Reactance Surface

Abstract: The propagation of two-dimensional waves guided along a reactance surface with a weak sinusoidal modulation is investigated by a perturbation procedure up to fourth-order in the modulation index n for the wave vector of the guided wave parallel to the grating vector The periodicity of the modulation is chosen such that only one fast leaky wave exists The correction to the propagation coefficient of the guided wave due to the reactance modulation is obtained up to fourth-order in n The correctness of the leakage coefficient up to fourth-order in n is verified by developing a power conservation relation valid up to that order in n The higher-order expression for the leakage coefficient indicates the presence of saturation for large values of n This higher-order treatment has yielded the correct exponential growth of the fast leaky wave perpendicular to the reactance surface and has revealed that some of the slow Floquet modes which do not carry power away from the reactance surface also contri

An Electroabsorptive CCD Spatial Light Modulator

Abstract: High-speed one- and two-dimensional spatial light modulation may be carried out using the electroabsorption effect in a GaAs buried-channel charge-coupled device (CCD). For photon energies slightly lower than the energy gap, the transmission through or along the surface of a CCD structure may be controlled by the signal charge in the wells, through the change in electric field with charge. The modulator is thus electrically addressable and it promises optical quality sufficient for coherent applications. The predicted performance has been determined for both Fourier transformation or spectral analysis and correlation/convolution. Although the modulation depth for normal-incidence illumination is only 10 to 20%, the calculated dynamic range is more than adequate for optical signal processing. In one-dimensional structures using a guided wave beneath the gate electrodes, the modulation depth approaches 100%, making the device an attractive alternative to acousto-optic modulators.

Guided wave coupling in integrated-optic gratings: normal incidence

Abstract: The coupling between the different guided modes of an integrated-optic waveguide grating filter is analysed. A numerical method based on a finite-difference scheme for the solution of this coupling problem in the case of normal incidence is presented. This allows one to study the influence of the grating profile on the coupling between guided or radiated waves. The exact numerical results are compared with approximate formulas for the coupling coefficient.

A numerical reconstruction of the permittivity profile of a stratified dielectric layer

Abstract: We consider the problem of determining the permittivity profile of a dielectric stratified medium of finite thickness terminated by a perfect conductor. The input data are the propagation and normalization constants of the guided modes, together with the values of the complex reflection amplitude for a TE-polarized monochromatic plane wave at different angles of incidence. In contrast to previous studies, our method of calculation is based on simple numerical procedures and uses only a physically justifiable regularization, quite different from the more involved regularization procedures that have been used elsewhere. The role of the guided modes is elucidated.

Guided-Wave Controlled Etalons

Abstract: Optical bistability in a nonlinear Fabry-Perot etalon can be controlled by several optical beams injected through the edges of the etalon. The control beams, which propagate transversely in the etalon, modify the refractive index, which in turn switches the etalon between its two stable states. The theory of operation of the device is presented, possible logical operations are discussed and experimental results from using an InSb electron and a CO laser are reported.

Ported coax intrusion detection sensor

Abstract: A ported coax intrusion sensor is a perimeter line sensor that utilizes VHF leaky coaxial cable(s) to generate guided waves for detecting an object near the cable(s). The theory of operation for ported coax intrusion sensors is described, including: 1) the basic mechanism of generating guided waves, 2) the propagation characteristics of these guided waves, 3) the scattering mechanism of the guided wave by a target, 4) the scattered signal formulation at the receiver, and 5) the signal processing techniques for detecting a moving target.

Analysis of the optical guided-wave fields by the retarded-potential method

Abstract: In this report,, it is shown that by applying Ewald-Oseen'g extinction theorem to a slab optical waveguide, the distribution of the guided-wave fields and the mode condition can be systematically obtained. Besides, it can be seen that the guided-waves are essentially eigen-states of the dipolar field of the waveguide. The characteristic properties of the optical guided-waves can be interpreted in terms of our elementary-excitation hybridization scheme.

The scattering by a dielectric spheroid of an electromagnetic surface wave travelling along a duct

Abstract: An electromagnetic surface wave travelling between conducting walls is incident on a small dielectric axisymmetric spheroid Reflection and transmission coefficients are found, to leading order, by a considerable generalization of the method used in an earlier paper The possibility of zero reflection of the incident wave mode is investigated

Waveband Noncollinear Guided-Wave Magnetooptic Interaction with Magnetostatic Surface Waves in YIG/GGG Waveguides

Abstract: Wideband noncollinear guided-wave magnetooptic diffraction and mode-conversion by the magnetostatic surface waves in the YIG-GGG waveguides have been observed and measured over a frequency band as large as 3 to 7 GHz by varying the DC magnetic field. I nteraction geometry, physical mechanisms, and some experimental results obtained at 1.152 optical wavelength are presented. This noncollinear guided-wave magnetooptic interaction configuration should result in a number of integrated optic devices for wideband communication and signal processing applications at electrically tunable microwave carrier frequencies. The potential advantages of the r esultant magnetooptic devices over the acoustooptic devices are also discussed.

Three-Layer Dielectric Stripline Filter For Guided-Wave Applications

Abstract: A novel wavelength filtering mechanism in a three-layer dielectric stripline structure is described. The waveguide consists of two high-index layers separated by a low-index layer in which the fields are evanescent perpendicular to the layer surfaces. The stripline is defined by a local extremum in the thickness of the middle, low-index layer. The analysis shows that upper or lower wavelength limits for propagation along the stripline can be set by proper choice of the thicknesses of the two high-index layers, if all layer refractive indices are specified. Outside these limits, the modes arc contained in the direction perpendicular to the layer surfaces, but are leaky in the direction parallel to them. The wavelength filtering mechanism is explained in terms of the wavelength dependence of the mode profile within and without the stripline. In this three-layer structure, for a particular mode, there is a critical wavelength for which the dependence of propagation constant on the thickness of the middle layer vanishes. At this wavelength, the mode does not see the stripline at all. On one side of this critical wavelength the effective index is at a local maximum along the stripline axis, while on the other it is at a local minimum. In the former case the structure acts as a dielectric stripline waveguide, containing the mode near the axis, while in the latter case the mode leaks away parallel to the layer surfaces. The structure gives sharp cutoffs in the transmittance vs. wavelength, with none of the oscillations beyond cutoff characteristic of distributed Bragg reflection filters.

Broadband guided-wave optical frequency translator using an electro-optical Bragg array

Abstract: We describe a new type of optical frequency translator which utilizes Bragg diffraction from a traveling index wave produced by an interdigitated electrode grating on a LiNbO3 surface waveguide. The grating is driven by a three‐phase electrical signal that results in a unidirectional wave with a fixed Bragg angle determined by the electrode spacing. The diffraction thus produces a single‐sideband suppressed carrier optical output. Measurements at 10 and 100 MHz have yielded greater than 90% carrier‐to‐sideband conversion efficiency with over 100:1 suppression of the carrier and unwanted sideband. The device should be operable from arbitrarily low frequencies up to several gigahertz.