LiTaO3/Silicon Composite Wafers for the Fabrication of Low Loss Low TCF High Coupling Resonators for Filter Applications

AbstractSAW devices are widely used for radio-frequency (RF) telecommunication filtering and the number of SAW filters, resonators or duplexers is still increasing in RF stage of cellular phones. Therefore, a strong effort is still dedicated to reduce as much as possible their sensitivity to environmental parameter and more specifically to temperature. Bounding processes have been developed at FEMTO-ST and CEA-LETI using either Au/Au or direct bonding techniques for the fabrication of composite wafers combining materials with very different thermoelastic properties, yielding innovative solutions for about-zero temperature coefficient of frequency (TCF) bulk acoustic wave devices. In the present work, this approach has been applied to (YXl)/42∘ lithium tantalate plates, bounded onto (100) silicon wafers and thinned down to 25μm. The leading idea already explored by other groups as mentioned in introduction consists in impeding the thermal expansion of the piezoelectric material using silicon limited expansion. 2GHz resonators have been built on such plates and tested electrically and thermally, first by tip probing. A dramatic reduction of the TCF is observed for all the tested devices, allowing to reduce the thermal drift of the resonators down to a few ppm.K-1 within the standard temperature range. We then propose an analysis of the frequency-temperature behavior of the device to improve the resonator design to use these wafers for industrial applications

Theory of imaging a photonic crystal with transmission near-field optical microscopy

While near-field scanning optical microscopy (NSOM) can provide optical images with resolution much better than the diffraction limit, analysis and interpretation of these images is often difficult. We present a theory of imaging with transmission NSOM that includes the effects of tip field, tip/sample coupling, light propagation through the sample and light collection. We apply this theory to analyze experimental NSOM images of a nanochannel glass (NCG) array obtained in transmission mode. The NCG is a triangular array of dielectric rods in a dielectric glass matrix with a two-dimensional photonic band structure. We determine the modes for the NCG photonic crystal and simulate the observed data. The calculations show large contrast at low numerical aperture (NA) of the collection optics and detailed structure at high NA consistent with the observed images. We present calculations as a function of NA to identify how the NCG photonic modes contribute to and determine the spatial structure in these images. Calculations are presented as a function of tip/sample position, sample index contrast and geometry, and aperture size to identify the factors that determine image formation with transmission NSOM in this experiment.Comment: 28 pages of ReVTex, 14 ps figures, submitted to Phys. Rev.

Computing the optical near-field distributions around complex subwavelength surface structures: A comparative study of different methods

Some 15 years ago, optical topographic signals with subwavelength resolution were obtained independently by several experimental teams. Since this exploratory period, a growing number of experimental configurations have been proposed and continuously developed. Simultaneously, this research field was supported by different theoretical works, aimed at developing our understanding of the interaction of optical fields with mesoscopic objects. Over the past three years, several theoretical frameworks have been proposed (Green's functions, field susceptibility, boundary conditions methods, multiple multipoles expansions, etc.). In this paper, an attempt at a careful comparison between two classes of numerical models is presented. Using the same test object, we discuss and compare the numerical solutions issued from a reciprocal-space perturbative method (Rayleigh approximation) and the solution originating from a direct-space integral approach (Green's function or field susceptibility). The discussion is given for different values of the relevant experimental parameters. The convergence of both approaches is investigated

Computational lens for the near field

A method is presented to reconstruct the structure of a scattering object from data acquired with a photon scanning tunneling microscope. The data may be understood to form a Gabor type near-field hologram and are obtained at a distance from the sample where the field is defocused and normally uninterpretable. Object structure is obtained by the solution of the inverse scattering problem within the accuracy of a perturbative, two-dimensional model of the object

French national cohort of first use of dalbavancin: a high proportion of off-label use

Dalbavancin is a glycopeptide antibiotic with a long half-life, recently marketed in Europe for skin and soft tissue infections (SSTI), but real-life use is not well-known. We aimed to describe all first prescriptions in France over an 18-month period. We performed a retrospective study on all adult patients who received at least one dose of dalbavancin from July 1, 2017 to September 31, 2018. Data were collected thanks to a standard questionnaire. Failure was defined as: persistent or reappearance of signs of infection; and/or switch to suppressive antibiotic treatment; and/or death from infection. We included 75 patients from 29 French hospitals. Main indications were bone and joint infections (BJIs) (64.0%), endocarditis (25.3%), and SSTIs (17.3%). Main bacteria involved were: Staphylococcus aureus (51.4%), including methicillin-resistant S. aureus (MRSA) (19.4%); and coagulase-negative staphylococci (CNS) (44.4%). Median MICs for staphylococci to vancomycin and dalbavancin ranged from 0.875 mg/L to 2.0 mg/L, and 0.040 mg/L to 0.064 mg/L, respectively. Dalbavancin was used after a mean of 2.3 ± 1.2 lines of antimicrobial treatment. Main treatment regimens for dalbavancin were a weekly 2-dose regimen (1500mg each) in 38 (53.2%) cases, and a single-dose regimen (1500mg) in 13 (18.3%) cases. Overall, at the patients\u27 last visit, clinical cure was observed in 54/72 patients, while failure was found in 14/72 patients. First uses of dalbavancin in France were mostly off-label. Most of them were due to BJIs, and often as rescue therapy for severe infections. Even in off-label situations, dalbavancin seems safe and effective

Electrodynamics in complex systems: Application to near-field probing of optical microresonators

This paper discusses recent theoretical efforts to develop a general and flexible method for the calculation of the field distributions around and inside complex optical systems involving both dielectric and metallic materials. Starting from the usual light-matter coupling Hamiltonian, we derive a self-consistent equation for the optical field in arbitrary optical systems composed of N different subdomains. We show that an appropriate solving procedure based on the real-space discretization of each subdomain raises the present approach to the rank of an accurate predictive numerical scheme. In order to illustrate its applicability, we use this formalism to address challenging problems related to nonradiative energy transfers in near-field optics. In particular, we investigate in detail the detuning of a microresonator probed by a near-field optical probe.</p