A set of floating electrodes and a relatively thick buffer layer of low-dielectric constant is interspaced between the coplanar RF transmission line and the LiNbO/sub 3/ substrate containing the optical wave-guide structure. The composite structure is designed to feature a 50-/spl Omega/ characteristic impedance, to have an effective dielectric constant equal to that of the optical wave for close velocity match, and to have a 3 dB bandwidth of 40 GHz. The purpose of the floating electrodes is to optimize the modulation sensitivity resulting in an improvement of about 6 dB. As a result, the RF power required for full modulation is lower than heretofore reported changing over the range from below 2 GHz to 20 GHz, from 44 mW to less than 70 mW. The close agreement between the theoretical and experimental values of the design parameters demonstrates the usefulness of the quasistatic assumption in the analysis of the composite structure.

Annealed proton-exchanged periodically segmented channel waveguides were fabricated in Z-cut lithium niobate. The propagation losses as a function of the duty cycle and the segmentation period are reported. Waveguiding was observed at large segmentation periods, up to 100 mu m. For duty cycles > 0.5, the propagation losses are nearly the same as measured for a continuous waveguide with the same width, namely similar to-1.45 dB/cm. With decreasing duty cycle, the mode expands in the transverse directions.

A series of measurements of nuclear stimulated desorption was performed for 103Ru, using thin ruthenium films irradiated by thermal neutrons. The magnitude, time dependence and electric charge state of the outgoing 103Rh flux was investigated. The utilization of monoenergetic electrons accompanying the 103Rh decay for thin film thickness measurement is considered.

Periodically segmented waveguides with periods of few tens of micrometers and nonconnected segments are studied experimentally in Ti:LiNbO3. The near-field patterns were found to expand with decreasing duty cycle but to be independent of the segmentation period. The measured segmentation losses vary between 0.5 and 2.5 dB/cm, depending on the period and the duty cycle. These results agree with a simple numerical model, based on two loss mechanisms: waveguide segmentation and surface relief related to Ti indiffusion.

47K atoms produced and separated at ISOLDE were embedded in a platinum foil by implantation, decaying therein to 47Ca. The foil was transferred to a vacuum chamber, and a sizeable fraction (around 10%) of the 47Ca was extracted from it by ohmic heating. The extraction procedure was repeated successfully for a number of times over a long period. An equivalent procedure failed to extract the 47Ca atoms out of a tungsten foil.

Buried waveguiding planar modes of well-defined profiles were observed in samples undergoing simultaneous Ti indiffusion and Li outdiffusion in a water vapor atmosphere. Each of these modes was distinctly excited by end-fire fiber coupling and suffered no loss by metal loading. An index profile which fits the mode shapes measured, and a mechanism is suggested based on the influence of a Ti-rich layer compound on the Li outdiffusion process.

A series of measurements of nuclear stimulated desorption was performed for compounds containing the isotopes 47Ca and Mo-99. A persistent charged component was observed in the desorbed flux of Sc-47 resulting from the decay of 47Ca. A transient charged component in the flux of Tc-99m was detected for some chemical forms of the Mo-99 compound.

A novel integrated-optic coupling configuration is proposed. The device operation is based on the confinement of the coupling zone to the length of a very short Fabry-Perot cavity. The cavity is electrooptically coupled with a parallel outcoupling guide. By employing accurate lithographic techniques for the fabrication of milled integrated mirrors, with total lengths of the order of 5-10 mum, devices 100 to 200 mum long can be considered. These can perform full coupling operation at bandwidths in the range of many tens of GHz with typically 12 to 15 dB extinction ratio. The same configuration can be also used for low frequency switching, where extinction ratio > 20 dB is expected. Calculated results are based on the parameters of Ti: LiNbO3 waveguides supporting 1.53 mum wavelength TM mode.

The spatial distribution of the spontaneous polarization In LiNbO3 may be changed by proton-exchange. The treatment of this crystal in benzoic acid causes the appearance of a layer of reversed-direction spontaneous polarization near the z+-surface. We have investigated proton-exchanged LiNbO3 utilizing both ferroelectric electron emission (FEE) and the Surface Laser Intensity Modulation Method (SLIMM) to measure the spatial distribution of spontaneous polarization. The FEE diminished sharply in benzoic acid-treated samples. SLIMM showed that the proton-exchange treatment caused reversal of the direction of spontaneous polarization in a layer about 1.2 mum thick on the z+-surface. No reversal occurred on the z-surface.

A method for ultraclean radioactive marking is presented, utilizing the process of nuclear stimulated desorption. It employs a sequence of two slow radioactive decays. The primary decay causes a nucleus to desorb from a substrate onto which it had been placed. The desorbing daughter nuclei, being themselves radioactive, then constitute an ultraclean marking flux. A manifestation of this mechanism for the special case of the 47Ca→47Sc→47Ti decay is described. An application to end-point detection in wet etching is presented and quantitatively simulated.

The decay chain 99Mo→99mTc wa and of their time dependence. Submonolayer quantities of a compound containing 99Mo were evaporated onto a stainless steel surface. The secondary decay was utilized to determine the desorption resulting from the recoil imparted during the primary decay. The initial nuclear delayed desorption probability measured was about 5%.