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We demonstrate, in both theory and experiment, 4-port, electrically tunable photonic filters using silicon contra-directional couplers (contra-DCs) with uniform and phase-shifted waveguide Bragg gratings. Numerical analysis, including both intra- and inter-waveguide couplings, is performed using coupled-mode theory and the transfer-matrix method. The contra-DC devices were fabricated by a CMOS-photonics manufacturing foundry and are electrically tunable using free-carrier injection. A 4-port, grating-based photonic resonator has been obtained using the phase-shifted contra-DC, showing a resonant peak with a 3-dB bandwidth of 0.2 nm and an extinction ratio of 24 dB. These contra-DC devices enable on-chip integration of Bragg-grating-defined functions without using circulators and have great potential for applications such as wavelength-division multiplexing networks and optical signal processing.

We propose to integrate grating-assisted asymmetric couplers with microring resonators for selective resonance excitation and control of coupling efficiency. A grating-coupled microring add-drop filter is experimentally demonstrated using a silicon-on-insulator technology compatible with complementary metal-oxide-semiconductor processing. A dominant longitudinal mode with a side-mode suppression ratio of 8 dB has been obtained across a broad spectral range of over 130 nm. The selected mode shows an out-of-band-rejection ratio of 19 dB and a quality factor (Q) of 25 000. The concept of integrating grating-assisted couplers for mode selectivity can be applied to other microring-based devices for high-Q, single-mode operations.

The results of measurements of the intrinsic phase-differences of titanium- indiffused lithium niobate waveguides, for use in integrated optics Pockels cell high-voltage sensors, are presented. The dependencies of the intrinsic phase-differences of these waveguides on their lengths and widths are investigated; a change of between 4.9 and 5.9 degree(s)/micrometers /mm was obtained. Also, the change in the intrinsic phase-difference as a function of both temperature and time was investigated; a typical change of 0.02 degree(s)/ degree(s)C/mm was measured and, following a small initial change, the bias was found not to drift with time. Some suggestions for possible post-processing of the output signals, of the integrated optics Pockels cell high-voltage sensors, to increase the dynamic range and to compensate for small changes in the bias, are presented.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A novel microstrip resonator structure for use with integrated Y-branch optical modulators fabricated in Ti:LiNbO3 is proposed. The legs of the structure are intended to act as the electrodes of the modulator, with light being directed into each of the output waveguides of the Y-branch on alternate half-cycles of the standing wave excited in the resonator; forming an optical commutator switch. Such resonators having Al2O3 substrates were designed, fabricated, and tested. Measurements on one such resonator, operating at 7.12 GHz and having an unloaded quality factor of 123, indicating that 50 V should develop across the ends of its legs for 35 mW dissipated power; the corresponding values, from the model used to design the resonator, were 179, 50 V,and 24 mW, respectively. Using the model it is shown that a similar resonator fabricated on LiNbO3 should be able to develop about 50 V for 100 mW dissipated power at 15 GHz.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A new optical commutator switch, capable of very high speed pulse generation and pulse multiplexing/demultiplexing, is proposed. It consists of an integrated optical Y-branch modulator and a `cul-de-sac' microstrip resonator. A possible compound digital optical modulator, using these optical commutators, is described. The results of measurements made on a cul-de-sac resonator, fabricated on an alumina substrate, and on optical Y-branch modulators, fabricated on z-cut lithium niobate substrates, are presented. For the resonator the unloaded quality factor was measured. For the optical Y-branch modulators the on/off ratios and percent guided powers were measured as functions of the applied voltage for several branch angles. The results indicate that optical commutators, of the type proposed, could be made. Copyright 1993 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

Coplanar slow-wave electrode structures capable of matching the velocities of microwaves to those of optical waves in compound semiconductor based electro-optic modulators are described. In such an electrode microwaves are slowed by periodically adding pairs of capacitive loading fins to the electrode to increase its capacitance per unit length, without obtaining a corresponding decrease in its inductance per unit length. Electro-optic modulators having wide bandwidths and requiring small amounts of modulating power may be realized by using slow-wave electrodes to achieve the velocity-match condition. The theory of operation of, and the results of some measurements on, electrodes of this type are presented. Copyright 1993 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

International audience; Silicon-on-insulator racetrack resonators can be used as multiplexers in wavelength division multiplexing applications. The free spectral range should be comparable to the span of the C-band so that a maximum number of channels can be multiplexed. However, the free spectral range is inversely proportional to the length of the resonator and, therefore, bending losses can become non-negligible. A viable alternative to increase the free spectral range is to use the Vernier effect. In this work, we present the theory of series-coupled racetrack resonators exhibiting the Vernier effect. We demonstrate the experimental performance of the device using silicon-on-insulator strip waveguides. The extended free spectral range is 36 nm and the interstitial peak suppression is from 9 dB to 17 dB.

To characterize z-cut Ti:lithium niobate Y-branch optical modulators, numerical simulations are performed showing that high on/off ratios are attainable without special Y-junction asymmetries or long electrodes. The effective index and 2-D finite difference beam propagation methods were used for the simulations. A modulator with a 2 deg. Y-branch was fabricated. The measured on/off ratios were 5:1 at 25 V, 12:1 at 50 V, and 60:1 at 75 V, corresponding to 4:1, 12:1, and 62:1 for the simulations for a wavelength of 632.8 nm. Copyright 1991 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

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.

A liquid level sensor based on etched D-shaped silica optical fibers is presented. The optical transmission of the sensor depends on the liquid level. The sensor can be realized as a continuous level sensor with a high resolution and requires only one fiber and one optical source and detector. We have demonstrated a sensor with a resolution of 1 mm. The sensor works for liquids with refractive indices greater than 1.45. We show that the sensor response is the same for increasing and decreasing liquid levels. © 2007 Society of Photo-Optical Instrumentation Engineers.

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.

We report on a push-pull integrated-optics Mach-Zehnder interferometer having one domain-inverted branch and one noninverted branch. It is fabricated in the c(+) side of a LiNbO(3) substrate. We achieve ferroelectric domain inversion in one branch of the waveguide by doping it more heavily with Ti than the other branch and by using a high-temperature treatment that raises the temperature above the doped Curie temperature of the one branch but not of the other. The cumulative electro-optic effect of the inverted branch is found to be opposite that in the noninverted branch when both are subjected to the same electric field.

When the effective-index method is used to reduce a three-dimensional refractive-index distribution to two dimensions, e.g., for use with the two-dimensional beam propagation method, strictly speaking, the effective index n(eff) cannot be calculated for nonguiding regions. Here a technique for obtaining values of n(eff) in such regions is described. The method begins with the index distributions in regions for which values of n(eff) are calculable and then perturbs them for those regions of interest. Using an electro-optic Y-branch optical modulator and a voltage-induced optical waveguide modulator as examples, we demonstrate this method and compare predicted results with measured results.

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. >