Search

Integrating photonics with CMOS electronics in silicon is essential to enable chip-scale, electronic-photonic systems that will revolutionize classical and quantum communication and computing systems. However, the lack of an on-silicon isolator, capable of blocking unwanted back reflections and ensuring the stable operation of the laser, precluded many previous demonstrations from providing single-chip solutions. For most optical systems employing a laser, magneto-optic isolators have been indispensable, but such isolators are incompatible with silicon. To stabilize on-chip lasers, reflections-cancellation circuits were proposed as a way to reduce the reflections going back to the laser. Yet, a stable laser against time-varying back reflections was never demonstrated. Here we demonstrate a stable quantum well-distributed feedback (QWDFB) laser against slowly time-varying reflections using a reflections-cancellation circuit (RCC) on a foundry-produced, silicon-photonic (SiP) chip. The optical spectrum and the relative intensity noise (RIN) of the laser when the RCC was running is comparable to when an isolator was used. By accurately locking the laser in a stable optical feedback regime, the RCC further enhances the QWDFB laser performance by reducing its linewidth by a factor of 100, down to 3 kHz. Both results are enabled using novel techniques in the design, calibration, tuning, and control of the proposed SiP RCC. The optical insertion loss of the RCC is less than 1.5 dB for reflections smaller than −20 dB and can yield isolation ranges of up to 64 dB. Our device paves the way towards the mass production of fully integrated, low-cost electronic-photonic silicon chips without attaching magneto-optic isolators between the laser and the SiP chip.

We demonstrate a method to predict the photolithography effects of a 193 nm deep ultraviolet (DUV) process, and we build a lithography model using physical measurements on a fabricated test pattern. Our model accurately predicts the proximity and smoothing effects that are characteristic of DUV lithography. We verify the accuracy of the model by visually inspecting the fabricated test patterns and comparing them to the predicted ones. Additionally, using predicted shapes, we compare experimental measurements on a benchmark device (the contra-directional coupler) against those of our predicted, computed responses. Our predictions show good agreement with the fabricated results using both verification methods. Lastly, we illustrate the design-for-manufacturability enabled by our model by demonstrating a design correction method for the contra-directional coupler that improves its compatibility with the DUV process.

A successful design, fabrication and test of silicon photonic circuits requires design tools, process design kits (PDKs), foundries for fabrication, and test facilities. This paper describes the complete design flow of photonic circuits using rapid-prototyping multiproject wafer foundry processes available in the SiEPIC program. The focus of this paper is on rapid prototyping based on electron beam lithography as an alternative and complementary to what is available via deep-UV lithography-based foundries. We describe in detail the PDK and the use of open-source and commercial tools for the design of optical filters, sensors, neuromorphic photonic processors, optical switches, and discuss test and packaging approaches for these designs. We demonstrate that a “germanium less” process can be used to build small systems featuring photoconductive detectors, electronics, and phase shifters.

Coupled silicon ring resonator filters offer high-order spectral features such as steep roll-offs, high extinction ratios, and wide pass-bands, which are attractive to many applications in telecommunications and quantum computing systems. However, so far, their sensitivity to fabrication and temperature variations have limited the usability of such filters in practical applications. Here, by using in-resonator photoconductive heaters (IRPHs) to both sense and tune the resonance conditions of ring resonators, we demonstrate automatic configuration and wavelength locking of multiring resonator filters to an input laser's wavelength. We demonstrate the automatic configuration of a four-ring Vernier filter across a 36.7-nm wavelength range spanning the entire C-band and the wavelength locking of the same filter to counteract a practical chip temperature variation of 65 ${^\circ }$ C. As IRPHs do not require additional material depositions, photodetectors, or power taps and use the same contact pads for both the sense and the tune operations, these results are achieved without compromising the cost or area of the devices. Furthermore, by localizing the feedback loops to only rely on the resonance conditions of adjacent rings, we present a tuning algorithm in which the number of iterations scales linearly with the number of coupled rings in the system. As this method does not rely on the output spectral shape of the system, it is, in general, applicable to a wide range of coupled resonator systems. Our results pave a path toward practical deployment of high-order and large-scale silicon ring resonator systems.

We demonstrate an apodization technique by tapering the corrugations of spiral Bragg grating waveguides on the silicon-on-insulator platform, for the fundamental transverse magnetic mode. The transmission and reflection responses of uniform and apodized spiral Bragg grating waveguides are experimentally compared to show higher sidelobe suppression ratios by the proposed apodization scheme. We also present an apodized, period-chirped spiral Bragg grating waveguide, and the group delay of the proposed device has been measured; the results show an efficient suppression in the ripples of the group delay response.

We examine inter-channel and intra-channel crosstalk power penalties between non-return-to-zero on-off keying (NRZ-OOK) wavelength-division-multiplexing (WDM) channels for microring-based silicon photonic interconnects. We first propose a new model that relates the crosstalk power penalty to the interfering signals power, the extinction ratio of the non-return-to-zero, OOK modulated “victim” channel, and finally the bit-error-ratio that the power penalty is referenced to. As for inter-channel crosstalk, the proposed model agrees well with our recent experimental measurements. We leverage this model to quantify crosstalk induced power penalties in a microring based WDM receiver. We also propose an optimization procedure to equilibrate the power penalty across channels. We then compare our model with intra-channel crosstalk measurements, where two NRZ channels are at the same wavelength and are simultaneously routed to different paths by two cascaded ring resonators. We remark that intra-channel crosstalk is very sensitive to the data rate of NRZ channels. As data rate increases, the observed disturbances exceed what models predict. Based on these observations, we propose an empirical modification of the original model for estimating intra-channel crosstalk power penalties in high ( $>$ 20 Gb/s) data rate situations.

We experimentally investigate the interchannel and intrachannel crosstalk of first- and second-order microring resonator (MRR) filters fabricated on a silicon-on-insulator platform. We find that there is an MRR radius that maximizes the wavelength division multiplexing channel count given a waveguide geometry, a maximum tolerable insertion loss, and a minimum permissible adjacent channel isolation. The measured power penalties due to interchannel crosstalk of two-channel demultiplexers based on first-order and series-coupled MRR filters are presented as functions of channel spacing and adjacent channel isolation. Next, we compare the intrachannel crosstalk of first-order, cascaded, and series-coupled MRR add-drop filters. Our results show that first-order MRR devices are unsuitable for simultaneous add-drop operation at high data rates and small channel spacings. Intrachannel crosstalk of cascaded and series-coupled designs are measured as functions of the data rate and the level of detuning between the MRRs. Low intrachannel crosstalk power penalties are demonstrated for cascaded and series-coupled MRR filters for data rates up to 20 Gb/s. Based on the measured results, we present requirements for the input-to-through response of add-drop filters that will ensure low intrachannel crosstalk.

We demonstrate, on the silicon-on-insulator platform, a modulator that uses a quarter-wave phase-shifted Bragg grating resonator. The modulator has open eye diagrams at data rates of up to 32 Gb/s. A bit error ratio of less than ${10}^{-10}$ is demonstrated using a $2^{31}-1$ pseudorandom binary sequence pattern at a data rate of 25 Gb/s.

We experimentally demonstrate apodized focusing subwavelength grating couplers for both the fundamental transverse electric (TE00) mode and the fundamental transverse magnetic (TM00) mode. A measured insertion loss of 3.2 dB with a 1-dB bandwidth of 36 nm has been obtained for the TE00 mode, and a measured insertion loss of 3.3 dB with a 1-dB bandwidth of 37 nm has been obtained for the TM00 mode. Back reflections of -24 dB and -21 dB have been obtained for the TE00 and TM00 modes, respectively.

Semiconductor ring resonators as the core components of instruments and devices have found applications in the areas of telecommunications and sensors. In this study, the feasibility of using ring resonators as solid-state angular rate sensors (gyroscopes) based on the Sagnac effect is assessed, and an extensive analysis of the optimal values of resonator length, coupling, and detuning is carried out, for the drop port of a double-bus ring, and for an all-pass, single-bus ring, for different values of propagation losses, consistent with different available technologies. We show that for both the all-pass and the drop-port configurations, optimally undercoupled rings show larger extinction ratios and, thus, better resolutions than critically coupled rings of the same length, contrary to our initial intuitive assumption that critically coupled rings should offer the best resolutions. Our analysis also shows that the ring resonator gyroscopes require a technology-constrained optimization, with the propagation loss as the main factor that hinders the resolution, and that determines the optimum values of all other parameters, namely length, coupling, and resonance detuning. According to our model, standard-chip-sized racetrack gyroscopes are suitable for rate- and tactical-grade applications for selected, currently feasible low propagation loss waveguides.

Analysis of wave propagation in the lower hybrid range of frequencies (LHRF) in the past was done using ray tracing and the Wentzel-Kramers-Brillouin approximation taking advantage of the very small scale of those waves. To include the effects of wave diffraction and focusing in this regime, full-wave simulation is necessary but requires significantly more computational power. In both ray tracing and full-wave simulations in the LHRF, it is also essential to include the self-consistent evolution of the electron distribution in response to the waves. This adds a considerable computational burden in constructing the stiffness matrix for the system [Valeo , “Full-wave Simulations of LH wave propagation in toroidal plasma with non-Maxwellian electron distributions,” 18th Topical Conference on Radio Frequency Power in Plasmas, AIP Conference Proceedings (2007)]. Advances in algorithms and the availability of massively parallel computer architectures have permitted the solving of the Maxwell-Vlasov system for wave propagation directly [Wright , Phys. Plasmas (2009), 16, July]. We will discuss the various modeling advances that have led to this capability, including various memory-management approaches, physics-motivated algorithm adaptions appropriate to the LHRF, and improvements in the matrix solver to minimize communication overhead when using thousands of cores on leadership-class computer platforms. Of particular importance have been the use of verification and validation techniques and the analytic approximations to the imaginary (pole residue) contribution to the plasma dielectric response.

The propagation characteristics of near-Z-axis lithium-niobate waveguides are investigated, considering the finite crystallographic-alignment tolerances. We expand on the previous models that have considered only the departures from the Z-axis in the plane of the substrate ("yaw") to include the effects of "pitch" and "roll." We find that a combination of yaw and pitch couples the major electric-field components of the fundamental quasi-TE and quasi-TM modes through off-diagonal permittivity components. When these two rotations are both larger than ~0.1deg, the imaginary coupling coefficient associated with the overlap of the major field components becomes larger than the real coefficient, associated with the coupling of the longitudinal TM component to the transverse TE component, that results from yaw alone. We show numerically, as well as experimentally, that unintentional crystallographic-alignment errors can result in substantial mode conversion, affecting the extinction ratio and linearity of Z-propagating modulators. The results also indicate that waveguides with intentional yaw will have mode-conversion characteristics that are highly sensitive to any unintentional pitch resulting from the boule slicing/polishing process. We highlight the importance of crystallographic alignment as well as the role of modal birefringence in suppressing undesired mode conversion

This paper describes a novel system for measuring the frequency response of electrooptic intensity modulators at millimeter-wave frequencies. The system measures |S21| in decibels electrical. In it, the electrical input signal to the modulator is generated by heterodyning two tunable lasers. The output of the modulator is then down-converted to a microwave frequency at which the output is easily measured. Measurements have been made up to 78 GHz using a 55-GHz photodiode as the mixer for the two lasers. In addition, our system tracks any frequency variations in the outputs of the lasers. Our system can also measure the linear response of the modulator if it is operated in nonlinear regions since it can reject higher order harmonics, due to nonlinearities, generated in the modulator

Summary form only given. This article presents a new hybrid electro-optic/inductive current sensor for metering and protective relaying applications. The sensor combines a Rogowski coil with a passive integrator located in the high-voltage environment. An integrated-optic Pockels cell (IOPC) having integrated electrodes provides optical isolation. Test results from 30 A to 30 kA show the sensor to be highly linear, exceeding 0.2% linearity standards. Temperature cycling tests show the ratio error to have a maximum value of 0.3% over the -30 to +70 /spl deg/C range.

This paper introduces the quadrature method for measuring voltage using one or more electric field sensors. To date, all high-voltage sensors, from conventional inductive transformers to modern optical voltage transducers, have one or more of the following traits in common: large size and weight, high-voltage electrodes in close proximity, expensive and potentially hazardous insulation, and capacitive voltage division. Combined with the use of small electro-optic field sensors, the quadrature method enables voltage sensor designs that are free of these traits and that are, therefore, particularly ideal for high-voltage applications. It also allows for a trade-off between the accuracy of the voltage measurement and the number of required electric field sensors. Numerical simulations demonstrate the effectiveness of this technique.

230 kV optical voltage transducers were constructed and tested. These transducers use three electric field sensors whose positions and outputs are selected and combined, respectively, in accordance with the quadrature method to obtain a voltage measurement. They meet IEC 0.2% class specifications and maintain 0.2% class accuracies even in the presence of electric field disturbances caused by local changes in geometry external to the transducer. The local changes in geometry used in the testing mimic those that may occur in a substation, e.g., installation or movement of equipment.

A novel passive polarization converter is presented using the elasto-optic effect in a ridge waveguide. A compressively stressed Si 3N 4 layer is deposited onto one side of the waveguide while a tensile layer is deposited on the opposing side. The average stress of the tensile and compressive layers is used to cancel the modal transverse-electric-transverse-magnetic (TE-TM) birefringence of the ridge waveguide. The difference in the tensile and compressive stresses induces birefringence with principal axes rotated 45deg from the TE-TM orientations. The method is demonstrated on an AlGaAs-GaAs waveguide at 1550 nm. We measure the orientation of the axes to be 46deg plusmn 1deg, demonstrating that complete mode conversion can be obtained without using periodic phase matching. Complete conversion is obtained in 1.16 mm with a waveguide loss of 0.1 dB/cm. Stability over temperature is also demonstrated.

Recently, we proposed a push-pull polarization-modulation scheme based on multiple repetitions of two InGaAlAs-InAlAs coupled quantum-well (CQW) structures. Additional numerical simulations showed one of the two CQW structures to be quite sensitive to layer thickness and compositional variations. Consequently, it would be challenging to reliably grow polarization modulators using this structure. Here, using the effective-mass envelope-function approximation, we design a more robust CQW structure to replace the sensitive one, and we also make improvements to the less sensitive of the two original structures

In this letter, an InGaAs/InAlAs coupled-quantum-well structure that is very robust to layer thickness and the compositional variations is reported. The robustness occurs because the structure's electrorefraction (ER) is based on the anticrossing of the two lowest energy light-hole wave functions. The structure is, thus, more appropriate for use in transverse magnetic modulators rather than in transverse electric modulators. The robustness of the structure is shown to be superior to that of a similar structure that has its ER effect based on the anticrossing of the two lowest energy electron wave functions

We present an optical heterodyne method for measuring amplitude and phase responses of electrooptic modulators over an ultrawide frequency range. The microwave input signal for the modulator under test (MUT) is produced by heterodyning the outputs of two lasers. The output of one of these two lasers is modulated by a subcarrier to produce dual tones separated by twice the subcarrier frequency. The output of the MUT is optically filtered to extract the components carrying the amplitude and phase information. Experimental results of measurements made up to 50GHz are presented

This letter describes a modified optical heterodyne down-conversion system for measuring the frequency response of wavelength-sensitive electrooptical devices at millimeter-wave frequencies. The new system is presented, and the frequency response of an injection-locked vertical-cavity surface-emitting laser is measured to up to 35 GHz

We present a simple nondestructive method for determining the cladding thickness, to the fiber flat, in D-shaped optical fibers. Here, the thickness of the cladding is determined by immersing a section of the fiber in a thermooptic oil and monitoring the power transmission as a function of the temperature of the oil. Fitting the response to theoretical models provides an accurate determination of the cladding thickness.

A novel broadband class-AB (CAB) microwave-photonic link is demonstrated using an AlGaAs-GaAs electrooptic mode-converter-based polarization modulator (PolM). The polarization-modulated signal is split into two paths, each independently optically biased to provide two electrooptic transfer functions operating close to, but on opposing sides of, their nulls. Experimental results at 2 and 4 GHz confirm that detection of the transfer functions in a differential detector provides excellent cancellation of second-order distortion and recreates the same third-order distortion as a quadrature-biased Mach-Zehnder modulator. Biasing the operating points near the null reduces optical carrier power, and hence, carrier-related noise, thereby increasing achievable spur-free dynamic range. The use of the PolM allows the CAB link to be implemented with a single modulator, reducing the matching requirements of dual modulator schemes and allowing third-order distortion-limited broadband operation.

Shorted-ground conductor-backed asymmetric coplanar strips support unwanted noncoplanar modes that adversely affect the performance of such transmission lines at higher frequencies. It is shown that coupling from the desired coplanar mode into the noncoplanar modes can be suppressed using slow-wave electrodes. This suppression scheme is verified by measuring the S-parameters of both conventional and slow-wave transmission lines of this type in the 0.05-50 GHz range.

A novel type of polarization conversion modulator, employing multiple repetitions of two novel InGaAlAs-InAlAs asymmetric coupled quantum-well structures, is proposed. The novelty of the proposed design is that, via the electrorefraction effect, it allows for a change in the TM mode's effective refractive index, which is opposite in sign to the change in the TE mode's effective refractive index. Numerical simulations based on the effective-mass envelope-function approximation show that the modulator provides not only an electrorefractive response similar to other quantum-well modulators but can also provide a low-chirp push-pull polarization modulation.

The inhibition of superconductivity in YBCO HTS films using ion implantation has shown itself to be a promising method for patterning HTS films for use in the fabrication of electronic devices. In this work we have shown that the carrier concentrations in YBCO films may be reduced in a controlled fashion using ion implantation, while retaining the superconducting properties of the films. YBCO films 100 to 140 nm thick commercially grown on SrTiO/sub 3/, were implanted with phosphorus ions, at 100 keV, with doses ranging from 1/spl times/10/sup 14//cm/sup 2/ to 1/spl times/10/sup 15//cm/sup 2/. Superconducting specimens with carrier concentrations ranging from /spl sim/10x10/sup 21//cm/sup 3/, for an unimplanted sample, to /spl sim/7/spl times/10/sup 20//cm/sup 3/ for a sample receiving an implant dose of 1/spl times/10/sup 15//cm/sup 2/, were obtained. The carrier concentrations were determined from Hall effect measurements.

Thin films of YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO), grown by pulsed laser deposition, were implanted with Si/sup +/ ions at energies of 30,60, and 90 keV and at doses ranging from 1/spl times/10/sup 13/ cm/sup -2/ to 3/spl times/10/sup 11/ cm/sup -2/. X-ray diffraction techniques were used to investigate the structural dependence on implant parameters and annealing conditions, while d.c. magnetization was measured to characterize superconducting properties. By implanting only the upper portion of the film, implanted Si/sup +/ ions, near the surface, inhibit the superconductivity by removing oxygen from the bottom YBCO lattice which still retains its original crystal structure.

A fiber-optic temperature sensor using evanescent fields in D fibers is presented. It works on the basis of optical attenuation brought about by coating the flat surface of the fiber with an external medium with a large thermooptic coefficient.

A novel microwave-photonic link is demonstrated using a unique AlGaAs-GaAs electrooptic mode-converter-based polarization modulator in a balanced output configuration. This enables suppression of common-mode intensity noise and optical-amplifier-induced beat noise using a polarization-selective balanced optical receiver. Unlike the conventional approach using a dual-output Mach-Zehnder modulator, the complementary output signals are combined naturally as orthogonal polarizations into one transmission fiber.

Reactive ion implantation (RII) has been used to inhibit superconductivity in oxide superconductor materials. By introducing ions which are chemically reactive with oxygen into a high temperature superconductor (HTS) oxide film, the conductivity of the material may be inhibited by the interaction of the implanted ions with the oxygen in the oxide. Both Si and B ions, with doses ranging from 1/spl times/10/sup 15/-1/spl times/10/sup 17//cm/sup 2/, were implanted into epitaxial YBCO films with injection energies ranging from 20-180 keV, depending on the film thickness. The implanted ions do not alter the overall crystal structure of the HTS film, but do inhibit the electrical conductivity and diamagnetism. Multiple ion implantations have also been employed to achieve uniform ion distributions. >

We have demonstrated uniform and sampled Bragg gratings in silicon-on-insulator strip waveguides with symmetric sidewall corrugations. The fabrication is based on 193-nm deep ultraviolet lithography using a single mask. The measured reflection spectra of sampled gratings exhibit ten usable peaks spaced by 4.2 nm, and show good agreement with theoretical predictions.

A fast numerical method using Gaussian quadrature, which takes only seconds on a microcomputer, is presented for calculating the fundamental mode sizes in optical channel waveguides. Variational expressions for the square of the propagation constant, beta /sup 2/, of the TE- and TM-like modes are derived using the vector wave equations. For channel waveguides with gradual refractive index distributions, these expressions approach the variational expression obtained using the scalar wave equation. To show the usefulness of the numerical technique the authors present the results for titanium indiffused lithium niobate channel waveguide which are commonly used in integrated optical circuits. Since these waveguides have gradual refractive index distributions, both types of expressions give the same results; however, it takes less time to compute the mode sizes when using the variational expression obtained from the scalar wave equation. The authors find the calculated mode sizes are in good agreement with published measurements. From the comparison process, best fit parameters are obtained, which give mode sizes close to the values published in the literature. For one special case the authors are able to obtain an analytical variational expression and they use it to test the accuracy of the numerical method. They find that the values of beta /sup 2/ given by both methods agree to six significant figures. >

A slow-wave electrode structure for integrated optic traveling-wave modulators in which the microwave's effective refractive index is matched to the optical wave's effective refractive index is described. The electrode structure is a capacitively loaded coplanar strip waveguide which can be formed in a single layer of metallization. Fabrication can be accomplished by a single photo-resist patterning, followed by an etching and a standard lift-off technique. Based on the use of gallium arsenide substrates and modern lithographic techniques allowing fabrication with micron scale resolution, slow-wave electrodes having a microwave effective refractive index of 3.5, as well as 50 and 75 Omega characteristic impedances are proposed. The theory of slow-wave electrodes is developed, and slow-wave electrodes have been designed, fabricated, and tested to verify the theory. Measurement results are found to agree well with the theory. >

A wide-band electrooptic polarization converter has been fabricated using slow-wave coplanar-strip electrodes on an AlGaAs-GaAs substrate. Microwave characteristics of the electrode have been measured up to 40 GHz. The microwave loss and the microwave index at 40 GHz are 0.4 Np/cm and 3.4, respectively. The optical measurements were done up to 20 GHz; a flat frequency response was observed.

Images associated with radio-frequency heating of low-confinement mode plasmas in the National Spherical Tokamak Experiment, as calculated by computer simulation, are presented. The AORSA code has been extended to simulate the whole antenna-to-plasma heating system by including both the kinetic physics of the well-confined core plasma and a poorly confined scrape-off plasma and vacuum vessel structure. The images presented show the 3-D electric wave field amplitude for various antenna phasings. Visualization of the simulation results in 3-D makes clear that -30° phasing excites kilo-volt per meter coaxial standing modes in the scrape-off plasma and shows magnetic-field-aligned whispering-gallery type modes localized to the plasma edge.

We present the design and experimental demonstration of a contra-directional grating-coupled racetrack resonator exhibiting the Vernier effect. The device consists of two racetrack resonators that are coupled together in a cascaded configuration. The input coupler in each racetrack resonator of the cascaded configuration consists of contra-directional gratings. The benefit of using contra-directional couplers is their small bandwidth, as compared to co-directional couplers that do not have gratings. The simulation results show that this device provides numerous performance advantages compared to cascaded racetrack resonators exhibiting the Vernier effect without contra-directional grating couplers. Specifically, we eliminate the free spectral range (FSR, i.e., in both the drop port and the through port) and show substantial improvement in the interstitial peak suppression and the through port insertion loss for the cascaded racetrack resonator with gratings, as compared to the case without gratings. In addition, experimental results are presented, which show an interstitial peak suppression of 29.3 dB, as well as the elimination of the FSR in the drop port and the through port.

In the above titled paper (ibid., vol. 18, no. 9, pp. 1082-1084, 1 May 06), a coding error in the model used led to errors in the results reported. Further explanation and correction is provided here.

This paper introduces permittivity-shielding which enables the measurement of voltage with very few electric field sensors. Voltage sensor designs using permittivity-shielding can exploit existing optical sensor technology without the need for the expensive and potentially hazardous insulation found in many modern optical voltage transducers (OVTs). Numerical simulations demonstrate that a voltage sensor consisting of 100 M/spl Omega/ shielding and six electric field sensors, or less, mounted inside an "off-the-shelf" stand-off insulator can achieve IEC 60044-2 0.2 metering class accuracies (

Coplanar strips, capacitively loaded with fins and pads and capable of achieving the microwave/optical wave velocity-match condition in GaAs- and InP-based electrooptic modulators, are described. Measurements on electrodes, fabricated to have dimensions appropriate for use in conventional, Mach-Zehnder-type modulators in the 5-40 GHz range, show that these electrode structures can be made to obtain the desired match between the microwave effective index and the effective indexes of AlGaAs and InGaAsP optical waveguides, while having loss coefficients ~0.7 Np/cm at 40 GHz.

Two modifications of the integrated optic Mach-Zehnder interferometer device are proposed which could be used to measure large electric fields, for example, in high voltage lines in utility substations. These new devices consist of an asymmetric slab and a strip-loaded diffused waveguide. They would merely be immersed in the field to be measured. Interrogation would be by optical fiber. The theory of operation of these devices is developed and examples are worked using the optical constants of possible materials.

A type of optical modulator first proposed by D.J. Channin (1971) in which an optical waveguide is induced in an electrooptic substrate by applying voltage between two parallel coplanar electrodes is reinvestigated. It is found that such devices will work for voltages much smaller than those used by Channin. The devices are fabricated with much smaller gaps between the electrodes and have an optical buffer layer to isolate the optical field from the electrodes. The theory of operation is developed and the device is modeled mathematically. The theory predicts that the optical field distributions of the modes of these devices become more highly confined with increasing voltage. >

Such devices would be useful for monitoring line voltages in, for example, SF/sub 6/ gas-insulated bus ducts. The theory of the devices is described and the results of tests on a laboratory prototype are presented. Furthermore, the design of a device monolithically integrating a capacitive divider and an integrated-optics Mach-Zehnder interferometer is proposed. >