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Grating couplers with nanoscale periodicity have been fabricated on silicon-on-insulator (SOI) substrates by electron beam lithography and reactive ion etching. A versatile experimental apparatus has been implemented to measure the efficiency of these gratings in coupling free-space radiation into planar waveguides. This coupling efficiency has been measured as a function of grating depth and the angle and wavelength of incident radiation. Coupling efficiencies of at least 5% and as high as 20% are demonstrated for wavelengths in the vicinity of 1550 nm and incident angles around 45deg.

We present experimental details of anodic bonding of optical fibers to silicon wafers having conventional thickness using an ultra-thin silicon layer as a stress-reducing layer. These results are expected to play a significant role in integrating microelectromechanical systems (MEMS) devices with optical fibers to form a new class of devices. Tensile bond strength measurements are presented as a function of bonding temperature that indicate optimum temperatures for both the optical-fiber to silicon bonding and silicon-to-silicon bonding. These measurements indicate that the maximum average tensile strength of the fiber-to-silicon bonds is 4.25 MPa at 400 °C and the maximum average strength of the thick silicon-to-silicon bonds is 7.93 MPa at 350 °C. We also demonstrate the simultaneous anodic bonding of up to five layers of silicon, each 250 μm thick. A 2D ANSYS simulation reveals that ultra-thin silicon does play a role as a stress-reducing layer.

We present the fabrication and initial testing of novel optically interrogated pressure and temperature sensors fabricated directly on optical fibers using microelectromechanical systems (MEMS) technology. A new micromachining process for use on a flat fiber end face that includes photolithographic patterning, wet etching of a cavity and anodic bonding of a silicon diaphragm is utilized. Two prototype pressure sensors, fabricated on 400 μm diameter multimode fibers, have been tested displaying an approximately linear response to static pressure (14–80 psi). A prototype temperature sensor, fabricated by anodically bonding an ultra-thin crystalline silicon onto a fiber end face, has been tested in the range 25–300 °C. A minimum detectable temperature variation of 6 °C is observed. Since these sensors are significantly miniaturized, they will find application in situations where small size is advantageous and where dense arrays may be useful.

Solutions of poly(p-phenylene benzobisthiazole) (PBZT) in methane sulfonic acid (MSA) were prepared and studied. Solutions with concentrations less than 0.04 wt % PBZT were characterized by dilute solution viscometry. Planar PBZT waveguides were spin-coated from a 0.5 wt % PBZT solution onto oxidized silicon wafers. The optical attentuation of the resulting polymer waveguides was measured and found to depend on both the thickness of the oxide layer on the silicon substrate and also the wavelength of the incident light. The lowest optical loss recorded for PBZT in this investigation was 4.81 ± 1.39 dB/cm at 834 nm. This work thus demonstrates the successful fabrication of PBZT into thin-film planar waveguides. The PBZT films prepared here also show improved optical characteristics over PBZT films prepared previously by either extrusion or spin coating. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1448–1456, 2000

Optical channel waveguides formed by focused ion beam (FIB) implantation-induced mixing of AlGaAs multiple quantum well structures and subsequent oxidation of the mixed regions have the potential of significantly reducing the size of integrated photonic waveguide structures. Since FIB implantation is a direct write process characterized by nanoscale precision, we suggest its use for forming channel waveguides having nanoscale (submicrometer) widths. Calculations presented for such channel waveguides show reductions in size by at least an order of magnitude are possible for directional couplers and other structures involving curved channel waveguide sections. Such size reductions would allow the realization of significantly higher levels of device integration than are now currently possible.

Channel optical waveguides have been formed on both GaAs and InP substrates utilizing deuterium passivation of the surface to provide planar confinement and etching to provide lateral confinement. Design criteria were established for obtaining single mode channel waveguides for the present case of small index changes and thick surface layers associated with deuterium passivation. Planar and channel waveguide operations were demonstrated and channel waveguide propagation losses have been measured. For GaAs channel waveguides, optical loss was measured as a function of channel waveguide width, ranging from 3 to 9 μm, with a minimum loss found for a width of 6.0 μm. Channel waveguide losses as low as 12.7 dB/cm for GaAs and 6.0 dB/cm for InP have been measured at λ=1.3 μm. For InP this loss value is close to the limiting value imposed by free carrier absorption in the semiconductor region below the passivated region. Since the waveguide loss due to free carriers can be reduced by increasing waveguide confine...

Curved, single-mode, silicon oxynitride optical ridge channel waveguides have been characterized by measuring mode field profile alteration, bending loss, and transition loss. The results were compared to theoretical calculations. Near field imaging of the channel mode field profiles showed the effect of bend radius on mode shape. Good agreement was obtained between the measurements and profiles obtained from two-dimensional (2-D) beam propagation method calculations. The exponential dependence of bending loss on bend radius and the variation of transition loss on the lateral offset between channels having different bend radius were successfully modeled by two simple theories.

Near field scanning optical microscopy (NSOM) has been used to investigate the guided mode intensity distribution in optical channel waveguides, phase-matched directional couplers, and symmetric Y-junctions. A near field measurement of the guided mode intensity profile across the optical channel waveguide has been performed and compared with model calculations. The near field guided mode intensity profiles above the waveguides were measured as a function of distance along the propagation direction of both a directional coupler and a Y-junction, providing a near field view of the spatial evolution of optical power in these structures.

Plasma-polymerized hexamethyldisiloxane (HMDS) films have been prepared as both planar and channel wave guides. The optical attenuation results measured in both the planar and channel HMDS wave guides were found to be similar, thus demonstrating that the inherent solvent resistance and chemical inertness of the plasma polymerized films allows the use of common photoresist techniques, including application of the photoresist, photomasking, and subsequent etching. This may be contrasted with wave guides made from conventional polymers, where careful consideration must be given to photoresist/polymer compatibility, because the photoresist solvents may adversely affect the underlying polymer and lead to degradation of the material during processing. © 1995 John Wiley & Sons, Inc.

Photon scanning tunneling microscopy (PSTM) has been used to characterize optical channel waveguides. Both He Ne laser and semiconductor diode laser wavelengths are utilized in the measurement of the evanescent field intensity associated with the propagating modes of optical waveguides. A tapered optical fiber tip, and also a semiconductor heterostructure tip attached to an optical fiber are employed for detection. Local values of effective refractive index are calculated from measurements of both TE and TM polarizations and compared to model calculations.

We have formed optical channel waveguides using focused ion beam (FIB) induced compositional mixing in an Al x Ga 1-x As multiple quantum well (MQW) structure. A focused Si ++ ion beam at 160 keV is implanted with a single scan of 5×10 14 cm -2 followed by rapid thermal annealing (RTA) at 950°C for 10 sec in order to achieve spatially selective compositional mixing. Raman microprobe spectra are used to characterize the lateral variation of compositional mixing transverse to the channel waveguides. Propagation loss of 4 μm and 8 μm wide channel waveguides are measured. Channel waveguide mode lateral intensity distributions are measured and used to determine the changes in effective refractive indices which are then used to estimate mixing depth.

A new configuration for a Mach-Zehnder interferometric electric field sensor device utilizing the electrooptic effect is reported. The lithium niobate device uses no metallic electrodes and operates solely by immersion in an electric field. Reverse poling of one arm of the interferometer provides opposing optical phase changes in the two interferometer arms when placed in an electric field. One fabricated device exhibits a measured minimum detectable field of 0.22 V/m/spl radic/Hz and a frequency response of greater than 1 GHz. Theoretical calculations show that detection of 0.11 V/m/spl radic/Hz is attainable while the upper frequency limit can exceed 6 GHz. >

The nonlinear phenomenon of polarization rotation in Ti:LiNbO3 optical channel waveguides was investigated using Raman microprobe microscopy. Polarization sensitive Raman selection rules permitted the identification of polarization rotation of the propagating transverse electric or transverse magnetic waveguide mode. From an analysis of the Raman scattered light collected orthogonal to the waveguide surface the threshold power necessary to initiate the process of mode conversion could be determined. In addition, the Raman microprobe was used to determine waveguide loss coefficients by collecting inelastically scattered light. The values obtained by this method were compared to those measured by collecting the elastically scattered light. A value for the asymmetric component, β15, of the photovoltaic tensor was calculated to be 7.8×10−13 A/W for the X‐cut, Y‐propagating and 3.8×10−14 A/W and 1.2×10−14 A/W for the rapid thermally annealed Z‐cut, Y‐propagating channel waveguides, respectively.

Raman scattering has been used to study the formation of tungsten silicide thin films. The tungsten films were sputter deposited on p‐type

We describe the fabrication, and initial testing of a novel optically interrogated, microelectromechanical system (MEMS) pressure sensor in which the entire MEMS structure is fabricated directly on an optical fiber A new micromachining process for use on a flat fiber end face that includes photolithographic patterning, wet etching of a cavity, and anodic bonding of a silicon diaphragm is utilized. We have employed both 200- and 400-/spl mu/m-diameter multimode optical fibers. A pressure sensor fabricated on an optical fiber has been tested displaying an approximately linear response to static pressure (0-80 psi). This sensor is expected to find application in situations where small size is advantageous and where dense arrays may be useful.

To examine aspects of an integrated photonic electric-field sensor, we calculate electro-optically induced refractive-index change in regular and reverse-poled LiNbO(3). Specifically, for y-propagating extraordinary modes, we determine how index change depends on electric-field magnitude and direction. To accomplish this, changes in index-ellipsoid shape and orientation are found by the use of a numerical eigenvalue procedure to diagonalize the impermeability tensor; then, refractive index is calculated by the use of a vector reference-frame transformation and a small perturbation approximation. A general formula is inferred from calculations for specific field directions. Electro-optic coefficients for reversepoled LiNbO(3) are obtained by application of a tensor reference-frame transformation to those of LiNbO(3). The index-calculation procedure has utility beyond the problem that is considered.

A rapid thermal annealing (RTA) system has been used to initiate indiffusion of Ti into LiNbO(3) for fabrication of optical channel waveguides. Four separate processes are investigated, each with different RTA temperature vs time variations followed by furnace heating. The sample processed with a fast initial ramp of temperature vs time to 875 degrees C yielded the lowest waveguide propagation loss of 1 dB/cm at a wavelength of 632.8 nm, compared with samples processed with other RTA variations and with a sample undergoing only furnace processing. Use of a dry O(2) ambient during RTA resulted in a smoother waveguide surface with no outdiffusion, when compared with use of a wet O(2) ambient.

The concept of having the effective refractive index of an optical waveguide mode be independent of temperature is introduced. It is shown that this concept should be realizable with a Corning 7059 glass thin-film waveguide supported on a SiO(2)-Si substrate for a waveguide thickness of 0.37 microm. Measurements of effective refractive index as a function of temperature confirm this prediction of temperature independence in that they show a very small variation with temperature for a 0.35-microm thick waveguide in comparison with that for a 0.98-microm thick waveguide.

Planar GaAlAs optical waveguides in which the waveguide core region is composed of multiple quantum wells are considered. Calculations of optical waveguide dispersion are performed to determine variations in effective refractive indexes for TE and TM modes and in the mode birefringence for large ranges of total waveguide thickness, number, and refractive index of well and barrier layers, and the ratio of well and barrier layer thickness. Ranges of these parameters which yield optical waveguides having unusually high birefringence and optical waveguides supporting single polarization planar propagation only are identified. >

Selectively oxidized vertical cavity surface emitting lasers (VCSELS) have been studied by spectrally resolved near field scanning optical microscopy (NSOM). We have obtained spatially and spectrally resolved images of both subthreshold emission and lasing emission from a selectively oxidized VCSEL operating at a wavelength of 850 nm. Below threshold, highly local high gain regions, emitting local intensity maxima within the active area, were observed; these were found to serve as lasing centers just above threshold. Above threshold, the near field spatial modal distributions of low order transverse modes were identified by spectrally analyzing the emission; these were found to be complex and significantly different from those measured in the far field.

A single polarization optical waveguide structure is introduced and demonstrated experimentally. The optical waveguide structure considered is a silicon nitride film deposited onto an oxidized silicon wafer so as to form a single-mode planar waveguide. Single polarization is achieved by choosing layer thicknesses, so that the attenuation due to substrate coupling for the TM mode is much larger than that for the TE mode. Calculations are presented to define ranges of design parameters over which TM attenuation can be 3-4 orders of magnitude higher than that for TE. In one sample having a TE loss of 0.28 dB/cm measured at a wavelength of 0.63 mu m a ratio of TM to TE attenuation of over 750 is experimentally demonstrated. >

Recent results from our laboratories on the design and characterization of optical waveguides are reviewed. Modelling of the design of channel optical waveguides is discussed and two means of experimental characterization that provide spatially local information are presented. Raman microprobe spectroscopy is used to explore the role of stress induced by a thin dielectric overlayer used to form channel waveguides in GaAlAs, and thus the role of photoelastic effects on waveguide behaviour. Photon scanning tunnelling microscopy is used to investigate local surface and index variations by probing the evanescent waveguide field.

Tunable photonic crystal (PC) waveguides have been designed using plane-wave expansion calculations for application to photonic integrated circuits. Wavelength selective propagation has been observed in silicon-on-insulator (SOI) PC waveguides fabricated by electron-beam lithography and inductively coupled plasma etching. Incorporation of DNA into an SOI PC lattice has been demonstrated, and novel tunable PC devices using biophotonic materials have been considered.

Incorporation of DNA into nanoscale wells in a silicon substrate has been demonstrated to show fabrication feasibility for optically tunable photonic crystal waveguides. A change in propagation characteristics due to DNA incorporation has been observed for a silicon-on-insulator photonic crystal waveguide.

Planar solid immersion mirrors have been implemented to inject grating-coupled infrared light from 30 mum wide rectangular channel waveguides into ~1.6 mum wide photonic crystal waveguides with high efficiency.

Freestanding, multimode optical channel waveguides formed by micromachining silicon are demonstrated. Fabrication utilizes standard microelectromechanical systems (MEMS) technology. Losses in the 0.57-0.80-dB/cm range are measured for channel waveguides with an air-silicon-air structure, whereas losses in the 1.12-1.52-dB/cm range are measured for channel waveguides with a SiO(2)-silicon-SiO(2) structure. Freestanding channel waveguides, along with optical fibers and other MEMS structures, can readily be mounted on a silicon MEMS platform to provide optimal alignment for maximizing optical coupling, and they are thus expected to be useful in devices that involve light and MEMS structures.

An analysis is presented that describes minimization of overall channel waveguide length in integrated optical circuits incorporating directional couplers and curved sections. Calculations are presented for LiNbO/sub 3/, GaAlAs, and SiO/sub 2/-Si based optical channel waveguides. The results demonstrate the presence of a minimum total length corresponding to a particular degree of field confinement. The value of overall length at the minimum is shown to be significantly lower than that for other values of field confinement allowing single-mode operation. >

This chapter examines the contribution of micromachining techniques in the specific context of fiber optically interrogated interferometer sensing technology. We focus on the sensing principles based on physical or mechanical effects that change the effective refractive index or phase of an optical signal induced by motion or deformation of micro-electromechanical systems (MEMS) structures. Many physical parameters such as temperature, pressure, force, and acceleration can be converted to a displacement or strain. Traditionally, fiber optically interrogated sensors are preferred over conventional electrical (piezoresistive, piezoelectric etc.) sensors in specific applications where small size, light weight, immunity to electromagnetic interference (EMI), compatibility with next-generation fiber-optic networks, and high temperature tolerance are required. Acquiring accurate, transient measurements in harsh environments of high-EM fields, vibration, and temperature, has pushed the limits of available sensor technologies. This has resulted a relatively a new sensor technology where a micromachined sensor element (or chip) “extrinsic” to an optical fiber is interrogated using an optical fiber (Figure 1). Although the fiber is not used as a sensor itself, its role is nevertheless very important for the operation of these sensors. By optically transmitting the measurement information without any electronics or optical source at the measurement site, it enables remote sensing with a virtually infinite transmission bandwidth and use of the sensor in harsh environments where electronics cannot operate. The micromachined sensor elements can contain integrated optic (IO) components such as optical waveguides and/or micro-mechanical structures such as diaphragms, cantilevers, and beams and are linked by optical fibers to a remote light source and receiver. Open image in new window FIGURE 1 Fiber optically interrogated micromachined “extrinsic” sensors in (a) reflective mode and (b) transmissive mode.

Optical microelectromechanical system pressure sensors based on the principle of Fabry-Perot interferometry have been developed and fabricated using the technique of silicon-to-silicon anodic bonding. The pressure sensor is then integrated onto an optical fiber by a novel technique of anodic bonding without use of any adhesives. In this anodic bonding technique we use ultrathin silicon of thickness 10 microm to bond the optical fiber to the sensor head. The ultrathin silicon plays the role of a stress-reducing layer, which helps the bonding of an optical fiber to silicon having conventional wafer thickness. The pressure-sensing membrane is formed by 8 microm thick ultrathin silicon acting as a membrane, thus eliminating the need for bulk silicon etching. The pressure sensor integrated onto an optical fiber is tested for static response, and experimental results indicate degradation in the fringe visibility of the Fabry-Perot interferometer. This effect was mainly due to divergent light rays from the fiber degrading the fringe visibility. This effect is demonstrated in brief by an analytical model.

We present results of near field scanning optical microscopy measurements performed on single mode AlGaAs ridge channel waveguides. The optical intensity distribution just above the surface of the waveguide structure has been measured by scanning a tapered, aluminum‐coated, fiber probe transverse to the waveguide propagation direction. Experimental results are compared with model calculations performed using both the effective index and beam propagation methods. An accurate description of submicron features in the intensity profile near the ridge edges, as well as the magnitude of the field outside the channel, requires the use of the beam propagation method.

In this paper we present novel anodic bonding of optical fibers to silicon wafers of conventional thickness. In this technique we use an ultra-thin silicon layer as an intermediate stress reducing layer. Anodic bonding of optical fibers to silicon enables integration of optical pressure sensors and temperature sensors for harsh and biomedical environments onto optical fibers by non-adhesive means. Non-adhesive integration of MEMS sensors onto optical fibers will lead to creation of new class of devices. Results include tensile bond strength test that indicate maximum average tensile strength of the fiber-to-thick silicon bonds is 4.29 MPa corresponding to bonding at 400/spl deg/C and ANSYS simulation which verify the role of ultra thin silicon as a stress reducing layer.

GaAs quantum well (QW) lasers with distributed Bragg reflection (DBR) Al0.3Ga0.7As/GaAs superlattice gratings have been fabricated by the single‐step, maskless focused ion beam (FIB) mixing. 200 keV Si++ FIB implantation with a beam diameter of ∼60–70 nm and a dose of 1014 cm−2 was used to obtain localized compositional mixing. The DBR grating period was 350 nm, corresponding to a third order grating matched to the emission from the 30 nm wide QW. Lasing operation was examined by optical pumping. With a pumping power 1.6× the threshold value, lasing modes were observed near 827 nm, with a spacing of 3 A and a linewidth of 1.5 A.

Near field microscopy is used to investigate the guided mode intensity distribution of optical channel waveguides and directional couplers with subwavelength spatial resolution. The directional coupler consisted of two single mode optical ridge channel waveguides formed with silicon nitride deposited on a lower cladding layer of SiO2 on a silicon substrate. A near field measurement of the guided mode intensity profile in the transverse direction parallel to the waveguide surface was performed across one of the optical channel waveguides. These variations are compared with model calculations. Similar transverse measurements of light propagating through a directional coupler were performed at many locations along the coupler, providing a view of the evolution of optical power transfer.

An optical pressure sensor has been fabricated which uses an integrated-optical ring resonator to measure the strain induced in a micromachined silicon diaphragm. A silicon substrate is etched from the side opposite the silicon oxynitride optical waveguides to produce a rectangular diaphragm whose long edge lies underneath a straight section in the ring. Pressure-induced changes in the resonant frequency of the ring are measured using a frequency swept laser diode. A linear response to pressure is observed for the TM mode with a sensitivity of 0.0094 rad/kPa. This pressure sensor is rugged, is amenable to batch fabrication, and it provides a link-insensitive readout. >

This program involved research on the utilization of near field optical microscopic and spectroscopic techniques to investigate spatial configurations on a nanometer scale of both integrated photonic structures and semiconductor nanostructures. We have made significant accomplishments in our research effort involving use of these near field techniques to investigate several important areas including photonic bandgap structures or photonic crystals, vertical cavity surface emitting lasers (VCSEL's), and optical waveguides including multiple interference structures. Near field microscopic and spectroscopic measurements performed on these structures provides more understanding of their behavior than can be ascertained in other ways; such understanding is expected to point toward improved device structures.

Pressure sensors utilizing MEMS technology for fabrication of the sensing element, interrogation by fiber optics, and which are suitable for propulsion applications are described. Devices utilizing micro-opto-electro-mechanical systems (MOEMS) technology are often better suited for harsh environments than electrically interrogated MEMS devices, so with sturdy packaging these optical devices may be useful to many propulsion applications. MOEMS pressure sensors can also be incorporated into arrays for detailed spatial characterization along with inherent high speed temporal characterization. Such characterization is expected to be very useful for propulsion systems. This presentation will first review optical-MEMS pressure sensor configurations. We will then concentrate on configurations most suitable for high speed applications in harsh environments. Examples of experimental results for static pressure test as well as for dynamic pressure test carried out in a shock tube demonstrating good linearity, sensitivity and time response will then be presented. Hybrid and monolithic array configurations will be presented. A discussion of the use of wavelength division multiplexing for efficient accessing of array elements will also be included.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Arrays of pressure sensors utilizing microelectromechanical systems (MEMS) technology for fabrication of the sensing element and interrogation by fiber optics are described. Optically interrogated MEMS devices are potentially more suitable for many propulsion applications involving harsh environments than electrically interrogated MEMS devices. Pressure sensor elements form a Fabry-Perot interferometer so that reflected light measures pressure. Rationale for the design of the geometry of sensor elements and array configurations will be presented. These devices are designed to provide sensitivity over a given pressure range, ease of fabrication, and array configurations useful for propulsion characterization. Sensor element and array fabrication will be discussed. These sensor elements are fabricated by etching shallow cavities in glass substrates followed by electrostatic bonding of silicon onto the glass over the cavity. The silicon is then etched to form the pressure sensitive diaphragm. Linear arrays having 6 elements will be described. Experimentally results for static pressure tests and dynamic pressure test carried out in a shock tube demonstrate reasonable linearity, sensitivity and time response.

Incorporation of DNA into nanoscale wells in a silicon substrate has been demonstrated to show fabrication feasibility for optically tunable photonic crystal waveguides. A change in propagation characteristics due to DNA incorporation has been observed for a silicon-on-insulator photonic crystal waveguide.

We report on the use of a Raman microprobe to investigate the nonlinear optical process of polarization rotation in Ti:LiNbO3 optical channel waveguides. Selection rules allow the Raman scattered signal collected in a direction orthogonal to the plane of the waveguide to provide information regarding the polarization state of the light propagating in the waveguide. From this data a threshold value of power necessary to initiate the polarization rotation is obtained and used to calculate a value of β15, an asymmetric component of the photovoltaic tensor. The value of β15 for an X‐cut, Y‐propagating channel waveguide was found to be 8×10−13 A/W and that for a rapid thermally annealed Z‐cut, Y‐propagating sample 4×10−14 A/W.

Near field scanning optical microscopy (NSOM) has been used to investigate the guided mode intensity distribution in channel waveguides, directional couplers, and Y-junctions. The intensity profile above the sample surface and transverse to the waveguide propagation direction has been measured using a tapered optical fiber to probe the guided evanescent field. The fiber probe was maintained at a constant height above the sample surface using feedback provided by performing these near field scanning measurements simultaneously with shear force microscopy topography measurements. Single mode channel waveguides were formed by etching a ridge in planar Si3N4/SiO2 structures and were excited with light of a wavelength of 830 nm. Measurements transverse to a channel waveguide revealed a cosine squared variation of intensity above the ridge and an exponential decay away from the ridge, as expected. Considerations for characterizing AlGaAs waveguides in this manner also are discussed. Multiple scans along the two waveguides of a directional coupler provided a detailed view of optical power transfer from one waveguide to the other and were in agrement with beam propagation method calculations. We anticipate that this type of measurement will provide a more detailed understanding of a central photonic structure, the channel waveguide, and its incorporation into a variety of device configurations.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Near field microscopy has been used to investigate the guided mode intensity distribution in a variety of optical channel waveguide structures. We have studied the optical field intensity distribution in channel waveguides, directional couplers, and Y-branches above the surface of the structures scanning transverse to the waveguide propagation direction. Single mode channel waveguides are formed by etching a ridge in Si3N4/SiO2 structures and excited at a wavelength of 833 nm. Measurements of the intensity distribution transverse to a channel waveguide reveal a cosine squared variation of intensity above the ridge region and an exponential decay away from the ridge region, in agreement with theoretical expectations. For more complicated structures, for instance the directional coupler, measurements along the two waveguides of the coupler provide a detailed view of optical power transfer from one waveguide to the other. Measurements also provide a detailed view of the evolution of the optical power in the Y-junction.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A high-speed low-skew system clock distribution network on a multichip module (MCM) is considered in systems perspective using system bandwidth, allowable system switching energy, number of clock signal fanout nodes supported, and the flexibility of the network structure to accommodate placement and routing requirements of various integrated circuits on MCM. Electrical H-tree networks modeled as lossless transmission lines are designed and evaluated along with guided wave optical H-tree networks. System performance analysis of optical and electrical H-tree networks on MCM suggests that optical H-tree clock distribution network has a superior capability compared to the electrical one by providing larger bandwidth, larger fanout, smaller system switching energy, and a flexible network configuration.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The complexity of optoelectronic systems is motivating the need for CAD tools which can simulate electronic and photonic device and circuit behaviors simultaneously and at multiple levels of abstraction. We describe such a tool, called AnaVHDL, which is being developed to concurrently simulate the behavior of optoelectronic systems consisting of digital, analog, and optical circuits. The approach is to extend the very high speed integrated circuit Hardware Description Language (VHDL) to describe the behavior of analog circuits and optical components, and to develop a simulation kernel which supports both discrete-event and continuous-mode simulation.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Advances in the development of a newly configured Mach-Zehnder interferometric electric field sensor device utilizing the electro-optic effect are reported. The integrated optical lithium niobate device operates solely by immersion in an electric field, using no metallic electrodes. Reverse poling of one arm of the interferometer results in additive optical phase changes in the interferometer arms when the device is placed in an electric field. Recently fabricated devices have exhibited a measured minimum detectable field of 34 mV/m per √Hz and a frequency response of greater than 10 GHz.

An electrically passive optical pressure sensor has been fabricated which uses a integrated-optical Y-junction ring resonator to measure the strain induced in a micromachined silicon diaphragm. A silicon substrate is etched from the side opposite the silicon oxynitride optical waveguides to produce a rectangular diaphragm whose long edge lies underneath a straight section in the ring. Pressure-induced changes in the resonant frequency of the ring are measured using a frequency swept laser diode. A linear response to pressure is observed for the TM mode with a sensitivity of 0.0094 rad/kPa. The transmissivity function of the resonator is derived and compared with measured response. This pressure sensor is rugged, amenable to batch fabrication, and it provides a link insensitive readout.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Near field scanning optical microscopy (NSOM) has been used to investigate the guided mode intensity distribution in optical channel waveguides, phase-matched directional couplers, and symmetric Y- junctions. A near field measurement of the lateral guided mode intensity profile was performed across the optical channel waveguide, and compared with model calculations. The near field guided mode intensity profiles above the waveguides were measured as a function of distance along both a directional coupler and a Y-junction, providing a near field view of the spatial evolution of optical power in these structures.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.