Abstract: We present a comprehensive report on recent experiments [Durfee and Milchberg, Phys. Rev. Lett. 71, 2409 (1993); Durfee, Lynch, and Milchberg, Opt. Lett. 19, 1937 (1994)] in which the channeling of intense laser pulses over distances much greater than a Rayleigh length was demonstrated using a two-laser-pulse technique. The first pulse creates a breakdown spark in a gas target, and the expansion of the resulting hot plasma forms a channel which guides a second pulse, injected into the channel after an appropriate delay. Data are presented for channels of 24 Rayleigh lengths (0.7 cm), while pulses have been channeled up to 70 Rayleigh lengths (2.2 cm), with up to 75% of the energy in the injected pulse focal spot coupled into the guide. In spite of the high intensities of the channeled beam (here up to ${10}^{14}$ W/${\mathrm{cm}}^{2}$), the propagation is linear and should remain so at even higher intensities. Single-mode, multimode, and leaky mode propagation of the channeled beam is observed, with the mode structure depending on the delay and the gas density. Along with these experimental results, we present a model of the laser-gas interaction and the resulting plasma hydrodynamics and calculate beam propagation and mode structure in plasma waveguides. A special property of a plasma waveguide is that the mode structure is wavelength independent, resulting in a wavelength-independent guiding condition.

Abstract: An optical illumination system comprising a waveguide (16) that accepts light generated by a diffuse light source (14) and transmits the light via total internal reflection. Attached on one face of the waveguide is an array of microprisms (90), with each microprism (90) having a light input surface (92) parallel to a light output surface (94) and at least two sidewalls (96, 98) tilted at an angle from the direction normal to the surface of the waveguide (16) such that light escapes from the waveguide, reflects off the tilted sidewalls (96, 98) and emerges from the microprism (90) as a spatially directed light source. An array of microlenses (80) may be positioned to accept the output of the microprisms (90) so that the light exiting from the microlenses (80) is a substantially collimated light source. The optical illumination system is advantageous for any application that requires a non diffuse or substantially collimated that is both energy efficient and contained in a low profile assembly.

Abstract: Part 1 Introduction: history materials outline of the book. Part 2 Foundations: Helmholtz equations dielectric interfaces geometrical optics. Part 3 Waveguide theory: general remarks formulations of the eigenvalue problem power flux in waveguides dispersion universal approximation schemes weakly guiding waveguides analytical solutions slab waveguides separable eigenvalue problems geometrical optics of the waveguide. Part 4 Beam propagation: fundamental principles classical BPM diffraction integrals improved BPM algorithms vectorial beam propagation method bidirectional beam propagation application of the BPM. Part 5 Mode conversion: Hermite-Gaussian beams coupling of gaussian beams gaussian optics fiber-to-chip coupling by microlenses optical tapers. Part 6 Codirectional coupling: coupled mode theory uniform directional couplers symmetrical couplers asymmetrical couplers transfer matrix theory Machzehnder devices directional couplers with periodic overlay. Part 7 Contradirectional coupling: phenomenological coupled mode theory Bragg gratings contradirectional coupler. Part 8 Planar spectrographs: theory of planar spectrographs focussing reflection gratings phased arrays. Appendices: application of photonics computer aided engineering component cost modelling mathematical background.

Abstract: PURPOSE:To improve the high output and low noise characteristic by constructing an active layer of a single quantum well layer and superlattice multiple quantum well layers provided on the upper and lower surfaces thereof and forming a ridged waveguide structure for obtaining a self-oscillating laser element. CONSTITUTION:An active layer is constructed of a single quantum well layer 5 and superlattice multiple quantum well layers 4, 6 provided on the upper and lower surfaces thereof, and composition, film thickness, and impurity concentration of respective layers 4, 5, 6 are caused by have predetermined values. A light waveguide layer, on the opposite side of a semiconductor substrate with respect to the active layer, has a mesa-stripe-like ridged part extending in the resonator length direction, and light absorption and current constriction parts are formed on the light waveguide layer with the ridge part at the both ends of the ridged part, and self-oscillation is effected. Therefore, the laser light distribution is controlled and the light absorption layer is provided at a predetermined position relative to the active layer, so that the effective refraction index difference in the lateral direction of the active layer can be caused to have a desired value. Thus, a high output characteristic required by a writing and erasing light source for an optical disk, and a low noise characteristic required by a reading light source can be obtained.

Abstract: A rigorous boundary contour mode-matching (BCMM) method is presented for the efficient calculation of the modal scattering matrix of arbitrarily shaped Hand E-plane discontinuities, junctions, and/or obstacles in rectangular waveguides. For the inhomogeneous waveguide region with general contour, the field is expanded in the complete set of cylindrical wave functions. The full-wave expansion allows the immediate rigorous inclusion of cascaded structures such as combined H- and E-plane bends. The efficiency of the method is demonstrated at the rigorous design of useful waveguide components which could not be modeled by mode-matching technique so far: cylindrical post-compensated H-plane T-junction, mitered H-plane and E-plane bends of arbitrary angle, cascaded H-/E-plane bends, circular post-coupled filter, E-plane filter with rounded corners, 180/spl deg/ rat race structure, and side-coupled dual TE/sub 311//TE/sub 113/-mode filter. The theory is verified by measurements. >

Abstract: Hollow glass waveguides with a 250-µm i.d. have been fabricated with a liquid-phase deposition technique that uses silica tubing as a base material. The losses of the 250-µm-bore guide measured at CO(2) laser wavelengths are as low as 2.0 dB/m. The straight losses for the hollow guides are in good agreement with theoretically predicted losses as a result of the nearly ideal structure of the guides. It is also shown that the guides have low bending losses, a nearly pure-mode delivery, and good high-power laser transmission. By proper design of the dielectric thickness, the guide is also able to deliver Er:YAG laser energy with a low loss of 1.2 dB/m for the 320-µm-bore waveguide. Because the hollow glass waveguide is very flexible and robust, it is quite suitable for medical applications.

Abstract: The invention concerns a dwarf wave mixer realized by windowing and is characterized in that a coplanar lead (320) is produced in the plating (212) of the substrate (211), the coplanar lead (320) dividing the plating (212) into two parts; in that the coplanar lead (320) is guided out along the narrow sides of the waveguide (11, 12); in that the coplanar lead (320) is connected to each of the two parts via a first and second diode (41, 42), respectively; and in that at least two slotlines (51 - 54) are produced parallel to the broad sides of the waveguide (11, 12) in the plating (212).

Abstract: We report quasi-phase-matched optical parametric amplification and oscillation in a periodically poled LiNbO(3) waveguide. Single-pass parametric gains of 4.1 dB, corresponding to 18%/W efficiency, were achieved at a signal wavelength of 1.55 microm with a pump wavelength of 782.2 nm. We formed a low-finesse cavity resonant at both signal and idler wavelengths by attaching mirrors to the waveguide end faces. Parametric oscillation was observed at wavelengths between 1.4 and 1.7 microm with a peak output power of 700 mW for pump wavelengths between 779 and 782 nm.

Abstract: We introduce and analyze a new type of high‐Q microcavity consisting of a channel waveguide and a one‐dimensional photonic crystal. A band gap for the guided modes is opened and a sharp resonant state is created by adding a single defect in the periodic system. An analysis of the eigenstates shows that strong field confinement of the defect state can be achieved with a modal volume less than half of a cubic half‐wavelength. We also present a feasibility study for the fabrication of suspended structures with micron‐sized features using semiconductor materials.

Abstract: An optical illumination system comprising a waveguide (16) that accepts light generated by a light source and transmits the light via total internal reflection. Attached on one face of the waveguide is an array of microprisms (28), with each microprism having a light input surface, a light output surface and at least one sidewall (33a) which is tilted at an angle ς from the direction normal to the surface of the waveguide (16) and further comprising at least two planar faces (31, 31a) such that light escapes from the waveguide (16), reflects off the tilted sidewalls (33a) and emerges from the microprism as a spatially directed light source. An array of microlenses may be positioned to accept the output of the microprisms (28) so that the light exiting from the microlenses is a substantially collimated light source. The optical illumination system is advantageous for any application that requires a non diffuse or substantially collimated light source that is both energy efficient and contained in a low profile assembly.

Abstract: Mach–Zehnder (MZ) waveguide interferometers integrated on SOI (silicon on insulator) for 1.3 μm operation are studied on the basis of the large cross‐section single‐mode rib waveguide condition and the free‐carrier plasma dispersion effect in Si wafer direct bonding SOI by back‐polishing. And the MZ interferometers are fabricated by using KOH anisotropic etching. Their insertion losses and modulation depths are measured to be 4.81 dB and 98%, respectively, at the wavelength of 1.3 μm when a forward bias voltage applied to a p+n junction is 0.95 V and the active zone length of the MZ interferometers is 816.0 μm.

Abstract: A channel waveguide on an erbium‐doped phosphate laser glass was fabricated by a dry silver‐film ion exchange technique, and its gain properties were studied experimentally. The propagation loss of the fabricated waveguide was 0.63 dB/cm at 1.3 μm. Er3+ concentration of 1×1020 ions/cm3 was chosen so that no concentration quenching occurred. This was confirmed by measuring a fluorescence lifetime of 8.4 ms at 1.54 μm. Gain of the fabricated waveguide was measured by using a Ti:sapphire laser at a wavelength of 980 nm and a laser diode of 1.532 μm producing pump and signal beams, respectively. The signal wavelength used for the experiments was shorter than the emission peak, and the measured gain of the 1.8 cm waveguide was comparable to the total loss. However, the model showed that lasing is expected at the emission peak with a 3.6 cm long waveguide fabricated in a similar manner. Calculation results showed that the potential gain of 8.8 dB can be realized with 250 mW pump power, and a 7.2 cm long waveguide provided that mode overlap can be increased by 20% and propagation loss can be reduced by 50%. No significant upconversion effect was observed up to 1.1×106 W/cm2 pump intensity.

Abstract: In this article, we present the characteristics of the ΔF=±1, ΔmF=±1, π microwave transitions which appear in the response of cesium beam resonators operating with U‐shaped waveguide Ramsey cavities bent in the plane of the H field. Such resonances are due to the presence in the cavity of microwave magnetic induction perpendicular to the static field direction. It is shown that the π resonance feature is derived from a pure two‐level atomic system interacting with four spatially separated oscillating fields. Good agreement is found between experimental data and theoretical predictions when we take into account the actual transverse microwave field profile in the cavity obtained with tridimensional electromagnetic field computations.

Abstract: This paper proposes a single-layer slotted leaky waveguide array antenna for mobile DBS reception. A single-layer feed structure is proposed, where the feed waveguide is in the same layer as the radiating waveguides. This results in the simple fabrication of slotted waveguide arrays, suitable for mass production. Short radiating leaky waveguides are used to get a large beam-tilting angle of about 50/spl deg/ for the horizontal installation of the antenna and a beamwidth broad enough to dispense with mechanical steering in the elevation plane. A prototype antenna sized 30 cm by 21 cm has a maximum of 74% efficiency and more than 69% efficiency within the DBS band. It also has a broad l-dB beamwidth of 7.5/spl deg/ in the elevation plane, which enables clear DBS reception by a picture tube display over about one-third the area of Japan without elevation tracking. >

Abstract: Device for use in adding or dropping light signals at predetermined center wavelengths to or from a wavelength division multiplex, fiber optic transmission system. The device includes an evanescent wave coupler having a coupling region formed from two single mode waveguides, the coupling region being formed so that there is substantially complete evanescent field coupling of light from one waveguide to the other in a predetermined wavelength band. Further, the device has a Bragg grating disposed in the coupling region in each of the waveguides.

Abstract: A recently developed laser-produced plasma channel is shown to be a promising means to produce an efficient, compact soft-x-ray laser. The channel provides a route for efficient high-power laser pumping through optical waveguiding of the pump. The channel also acts as a waveguide for generated soft x rays, as it has wavelength-independent mode structure. It is shown that channel creation and guided laser pulses of moderate duration and energy can be highly effective in producing nonequilibrium gas density plasmas and candidate ions for collisional and recombination laser schemes. The nonequilibrium behavior of these plasmas can be exploited to generate substantial population inversions.

Abstract: An optimized waveguide structure enables the functional integration of various passive optic components on a single substrate. The optimized waveguide structure is characterized by a thicker core layer than used for square core waveguides and a core width that changes according to different functional regions of the optic circuit within which it is incorporated. The height (H) of the waveguide core is determined by the thickness of the core layer defined during the fabrication process and is ideally uniform across the circuit. The width (W) of the core, however, is changed between functional regions by the photo-lithographic mask and the chemical etching during the fabrication process. By way of example, an optimized waveguide structure for a P-doped silica planar waveguide with a Δ approximately 0.6% for wavelength λ=1.2-1.7 μm, has a single uniform height of H=6.7 μm and a width that changes between W=4 μm in a coupler region, W=5.5 μm in a bend region, W=9 μm in a fiber coupling region, and W=10 μm in a phase grating region of a Dragone router. Adiabatic tapers are used as transition regions between regions of different core widths.

Abstract: This paper presents investigations on leaky wave antennas that are modeled by periodical illumination of light on a grounded semiconductor slab waveguide using an asymptotic method of singular perturbation procedure based on multiple scales. Analytical results clearly show that the periodical illumination strongly affects the radiation characteristics such as efficiency and the radiation angle. The dominant effects are studied quantitatively and are outlined in the performance diagrams as a function of optically induced plasma density and the grating period. Initial experimental results at Q band using silicon slab guide under an array of 820-nm LED CW excitation are also reported and are in relatively good agreement with the theory. >

Abstract: An optical filter, such as a wavelength-division multiplexer, demultiplexer, or optical router, in which several single-mode waveguides are coupled to the sides of an optical interaction region containing a wavelength dispersive element that collects light from one or more input waveguides inputting light to the interaction region and disperses it according to wavelength to one or more output waveguides outputting wavelength-separated light. According to the invention, a multi-moded waveguide is interposed between one or more of the single-moded waveguides and the optical interaction region. It has a predetermined length to create at one end a multiply peaked image of a singly peaked profile presented to it at the other end, thus being a multi-mode interference (MMI) filter that presents a flatter filter profile at the interface between the MMI and the optical interaction region and affords reduced filter sensitivity to wavelength drift of an optical signal. The wavelength dispersive element is preferably an arrayed waveguide grating between two optical interaction regions at the input and output sides. Several optical switches, multiplexers, and add-drop circuits have architectures that beneficially use the filter of the invention.

Abstract: This paper presents some numerical implementation issues and the performance of Berenger's perfectly matched layer (PML) boundary condition for modeling wave propagation in waveguide structures by the finite-difference time-domain (FDTD) method. The relation between the thickness and the conductivity profile of the perfectly matched layer is studied and a guideline for the selection of PML parameters is given. It is shown that the standard Yee's time-marching scheme results in virtually the same numerical solution as the exponential time-marching scheme. Numerical tests are provided for parallel-plate and rectangular waveguides and microstrip lines. It is found that PML is very effective in absorbing TEM and quasi-TEM waves, as well as nonTEM waves somewhat above cutoff frequencies, but ineffective in absorbing evanescent waves and nonTEM waves near cutoff frequencies. The reason for the ineffectiveness of PML for absorbing evanescent waves is explained. Comparative study of PML and Higdon's boundary condition shows that high-order Higdon's boundary condition can reach the same performance of 16-cell PML and can be adjusted for absorbing evanescent waves, but PML is in general more robust to implement. Performance of the boundary condition obtained by combining PML and Higdon's boundary condition is evaluated.

Abstract: An efficient hybrid mode-matching finite element (MM/FE) method is applied for the rigorous analysis of waveguide filters composed of homogeneous standard waveguide cavities together with waveguide coupling sections of nearly arbitrary cross-section. To demonstrate the efficiency of the method, a simple two-pole circular waveguide dual-mode filter is analyzed where the orthogonal modes are coupled by obliquely positioned rectangular post elements with rounded edges and the coupling to the rectangular port waveguides is provided by rectangular irises with rounded corners. Moreover, a four-pole filter is shown where the dual-mode coupling is achieved by asymmetrically located irises. The theory is verified by excellent agreement with measurements. >

Abstract: A full wave, formally exact solution is obtained for the problem of scattering at the junction of a rectangular waveguide and a larger circular waveguide. The general case of an arbitrary offset of the waveguide axes is considered. E-field mode matching over the rectangular aperture of the smaller guide is facilitated by a transformation of the circular cylindrical Bessel-Fourier modal fields of the circular guide into a finite series of exponential plane wave functions in rectangular coordinates. This permits an analytical finite series solution for each of the elements of the E-field mode matching matrix [M] from which the scattering matrix [S] of the junction is easily obtained. Numerical evaluation of the S-parameters for the dominant TE/sub 10/ (rectangular) and TE/sub 11/ (circular) modes in the cases of junctions with no offset and with offset is presented. Moreover, the practical case of a circular cavity resonator with smaller input and output rectangular guides is considered and excellent agreement is found between the calculated and measured S-parameters. >

Abstract: By invoking the slow-wave approximation, the wave equation resumes the form of the Fresnel equation. Codes developed previously for the paraxial beam propagation can be extended to simulate the backward reflection and diffraction at any angle. Results of planar waveguide gratings and a beveled corner bend are presented. >

Abstract: A full-wave analysis is presented for the propagation characteristics of a through hole via connecting two semi-infinitely long transmission lines in multi-layered packaging environment. The current distribution on the via and a section of transmission line is solved under the thin wire approximation by the moment method and the scattering parameters are extracted by the matrix pencil method. The Green's function in multilayer packaging environment is derived by applying the image theory and evaluated by the help of the Poisson summation formula. Numerical results are included to investigate the frequency dependent propagation characteristics for via structures with various geometrical parameters, e.g., the via height, wire diameter, and distance between two ground planes. The excitation of the radial waves due to the current distribution on the via is also discussed in detail. >

Abstract: In this paper, we present a structure called a non-leaky coplanar (NLC) waveguide with conductor backing. It is a multilayered structure with two possible configurations. The spectral domain approach with a complex root searching procedure is used to investigate leakage phenomena. The simulation results confirm that the leakage in conductor-backed coplanar waveguide (CBCPW) occurs in the form of wave in the parallel plate waveguide with infinite width. The results show that the leakage in the multilayered structure can be removed if the geometrical and material parameters of the structure are chosen appropriately. Experiments were carried out to investigate the transmission of these structures. It was found that the resonance in the transmission of finite-width conductor-backed coplanar waveguide (FW-CBCPW) is caused by the energy leakage from the dominant CPW mode. The resonance is eliminated in the NLC waveguides. These NLC waveguides are feasible and practical in the uniplanar MMIC design due to their planar nature. >

Abstract: Curved waveguides with strong lateral modal confinement have been fabricated on InGaAsP/InP by etching through the waveguide core. This has resulted in extremely sharp bends (radii as small as 30 Im) with negligible bend loss, enabling fabrication of very low loss 90" turns on a chip area as small as that of a corner mirror.

Abstract: An integrated optical isolator based on nonreciprocal conversion from a fundamental TM mode to a higher‐order TE mode is proposed and experimentally demonstrated. The isolator is realized using a single‐mode rib channel waveguide in Ce‐substituted yttrium iron garnet which has a very large Faraday rotation. 24 dB isolation is obtained at a wavelength of 1550 nm.

Abstract: An optical detector for use in liquid chromatography systems or capillary electrophoresis systems comprises an optically transparent detector body through which an analyte channel extends, a fluid containing the analyte being adapted to be guided through said analyte channel. In order to increase the detection sensitivity, the light path between a light source introducing light and an optoelectric sensor element of the liquid chromatography system or capillary electrophoresis system is constructed as a Bragg waveguide structure extending at least along a sublength of said analyte channel essentially in the channel direction.

Abstract: The authors present a filter designed to flatten the gain of an EDPA system over a 30 nm bandwidth. The filter consists of cascaded couplers and delays, and is fabricated with planar silica waveguides. The design is based on Fourier expansion, and our approach is generally applicable to other complex filters and other waveguide structures.