Search

International audience

National audience

International audience; &nbsp

International audience; In this work, electromechanical coupling factor, K2, and Temperature Coefficient of Frequency (TCF) of Bulk Acoustic Wave (BAW) resonators based on high aspect ratio ridge structures in 42°Y-X LiTaO3 (LT) and Z-cut LT single crystals with different Li stoichiometries were studied experimentally, analytically and by combined finite element / boundary element analysis. Initially, analytical analysis was carried out to determine the contribution of different elastic constants in thickness field excitation of shear modes in high aspect ratio ridge structures. The analysis shows shear modes that are dependent on C44 in ridge resonators based on 42°Y-X and Z-cut LT crystals. However, the measured frequency response of such structures exhibited many spurious resonances, making difficult the direct extraction of acoustical parameters. A fitting procedure that allows taking into account several resonances occurring simultaneously in a restricted frequency range was used. Higher K2 and more positive temperature dependence of frequency were determined for ridge structures in nearly stoichiometric crystals compared to those of equivalent structures in congruent ones.

International audience; Beam self-trapping by pyroelectric effect is reported in a LiNbO3 film. The underlying physics specific to this arrangement is especially characterized by a response time orders of magnitude faster than in bulk LiNbO3

International audience

International audience; We report on low-loss vertical tapers for efficient couplingbetween confined LiNbO3 optical ridge waveguides and Single ModeFibers. 3D-Pseudo-Spectral-Time-Domain calculations and Optical-Coherence-Tomography-based methods are advantageously used for thenumerical and experimental study of the tapers. The tapered-section is donesimultaneously with the ridge waveguide by means of a circular precisiondicing saw, so that the fabrication procedure is achieved in only two steps.The total insertion losses through a 1.6 cm long ridge waveguide aremeasured to be improved by 3 dB in presence of the taper. These taperedridgewaveguides open the way to the low-cost production of low-lossphase modulators or resonators.

Over the past decades, minutiarization and compacity have become a focus subject for companies specialisedin the manufacturing of radio-frequency components. Active components are typically manuafctured onsilicon wafers with well-known structuring methods. Passive ones are often manufactured on single cristalsuch as Quartz or Lithium Niobate, especially for acoustic wave generation or lightwave guiding. Theguiding of optical or acoustical waves leads to the manufacturing of sensors or filters which can be usedfor telecommunications or for the industry. Improvement in waveguiding allows for less power-consuming andmore compact devices but a 3D-structuring is usually required. This technology readness is high leveled forsilicon structuring but not for single crystals such as Lithium Niobate. This work presents the development andthe manufacturing of high aspect ratio three-dimensionnal structures in single-crystals using precise sawing.These structures show an optical waveguiding capability which allow the improvements of electro-opticmodulators or filters. Combined with a periodic reversing of Lithium Niobate polarization, these structuresallows for bulk acoustic wave generation leading to high electromechanical coupling and equivalent phasevelocity resonant modes. In non-linear optic field, this kind of structures lead to the improvement of secondharmonic generation e_ciency by reducing the cross section of waveguide. The manufactured devices in theframework of this project can actuelly be used in several domains of physic.; La miniaturisation est l’objectif actuel de tous les fabricants de composants radio-fréquence depuis plusieursdécennies. Si les composants actifs pour la microélectronique sont fondés sur la structuration de plaquesde silicium, les composants passifs reposent sur l’utilisation de cristaux tels que le quartz ou le niobate delithium. Ce dernier est particulièrement utilisé quand il s’agit de générer et exploiter des ondes élastiques, ainsique pour le guidage de faisceaux lumineux afin de réaliser des filtres ou des capteurs sensibles à différentsparamètres environnementaux. L’amélioration du guidage de ces ondes permet un gain en consommation et encompacité des dispositifs mais nécessite une structuration de la matière souvent tridimensionnelle. Cette étapetechnologique clé est industriellement mature pour la mise en forme du silicium, mais s’avère di_cilementtransposable à des matériaux tels que le quartz ou le niobate de lithium. Les travaux présentés dans cemanuscrit visent à réaliser des structures tridimensionnelles à hauts facteurs de forme dans des matériauxmonocristallins à l’aide d’une scie circulaire de précision. Des structures utilisant l’inversion périodique dedomaine ferroélectrique seront réalisées afin de les utiliser pour y guider des ondes élastiques possédant descouplages électromécaniques particulièrement élevées. Le guidage d’ondes optiques par le biais de ces mêmesstructures permet une amélioration du confinement par rapport aux systèmes de guidage massifs classiquescouramment utilisés pour la réalisation de filtre ou de modulateur électro-optiques. En utilisant conjointementle guidage d’ondes optiques et les domaines ferroélectriques alternés, les structures ainsi découpées permettentl’apparition de phénomènes optiques non-linéaires exaltés par l’amélioration du confinement. Ces structuresont ainsi montré leur intérêt dans plusieurs domaines de la physique avec un champ applicatif particulièrementvaste

Over the past decades, minutiarization and compacity have become a focus subject for companies specialisedin the manufacturing of radio-frequency components. Active components are typically manuafctured onsilicon wafers with well-known structuring methods. Passive ones are often manufactured on single cristalsuch as Quartz or Lithium Niobate, especially for acoustic wave generation or lightwave guiding. Theguiding of optical or acoustical waves leads to the manufacturing of sensors or filters which can be usedfor telecommunications or for the industry. Improvement in waveguiding allows for less power-consuming andmore compact devices but a 3D-structuring is usually required. This technology readness is high leveled forsilicon structuring but not for single crystals such as Lithium Niobate. This work presents the development andthe manufacturing of high aspect ratio three-dimensionnal structures in single-crystals using precise sawing.These structures show an optical waveguiding capability which allow the improvements of electro-opticmodulators or filters. Combined with a periodic reversing of Lithium Niobate polarization, these structuresallows for bulk acoustic wave generation leading to high electromechanical coupling and equivalent phasevelocity resonant modes. In non-linear optic field, this kind of structures lead to the improvement of secondharmonic generation e_ciency by reducing the cross section of waveguide. The manufactured devices in theframework of this project can actuelly be used in several domains of physic.; La miniaturisation est l’objectif actuel de tous les fabricants de composants radio-fréquence depuis plusieursdécennies. Si les composants actifs pour la microélectronique sont fondés sur la structuration de plaquesde silicium, les composants passifs reposent sur l’utilisation de cristaux tels que le quartz ou le niobate delithium. Ce dernier est particulièrement utilisé quand il s’agit de générer et exploiter des ondes élastiques, ainsique pour le guidage de faisceaux lumineux afin de réaliser des filtres ou des capteurs sensibles à différentsparamètres environnementaux. L’amélioration du guidage de ces ondes permet un gain en consommation et encompacité des dispositifs mais nécessite une structuration de la matière souvent tridimensionnelle. Cette étapetechnologique clé est industriellement mature pour la mise en forme du silicium, mais s’avère di_cilementtransposable à des matériaux tels que le quartz ou le niobate de lithium. Les travaux présentés dans cemanuscrit visent à réaliser des structures tridimensionnelles à hauts facteurs de forme dans des matériauxmonocristallins à l’aide d’une scie circulaire de précision. Des structures utilisant l’inversion périodique dedomaine ferroélectrique seront réalisées afin de les utiliser pour y guider des ondes élastiques possédant descouplages électromécaniques particulièrement élevées. Le guidage d’ondes optiques par le biais de ces mêmesstructures permet une amélioration du confinement par rapport aux systèmes de guidage massifs classiquescouramment utilisés pour la réalisation de filtre ou de modulateur électro-optiques. En utilisant conjointementle guidage d’ondes optiques et les domaines ferroélectriques alternés, les structures ainsi découpées permettentl’apparition de phénomènes optiques non-linéaires exaltés par l’amélioration du confinement. Ces structuresont ainsi montré leur intérêt dans plusieurs domaines de la physique avec un champ applicatif particulièrementvaste

International audience; We report on low-loss vertical tapers for efficient coupling between confined LiNbO3 optical ridge waveguides and Single Mode Fibers. 3D-Pseudo-Spectral-Time-Domain calculations and Optical-Coherence-Tomography-based methods are advantageously used for the numerical and experimental study of the tapers. The tapered-section is done simultaneously with the ridge waveguide by means of a circular precision dicing saw, so that the fabrication procedure is achieved in only two steps. The total insertion losses through a 1.6 cm long ridge waveguide are measured to be improved by 3 dB in presence of the taper. These tapered-ridge waveguides open the way to the low-cost production of low-loss phase modulators or resonators.

This paper investigates some properties of vibrating beam resonators in length extensional mode and mainly the energy loss by coupling between the beam and the frame of the device. The resonators were designed and built using an alternative material of quartz, the langasite (LGS), which has some interesting piezoelectric and thermal properties. The process of microfabrication is based on the anisotropic chemical etching whose main advantage is that it is a low cost process. Several characterizations of the devices were performed to control first the shape of the cantilever and the size of the tip at its end. Second, electrical and optical measurements were conducted to obtain the resonant frequency for extensional mode and to detect the shear mode of vibration. The results were compared with the theoretical ones which have been obtained using a FEM simulator. In this paper, we proved the interest of such devices to obtain probes with high performances for FM-AFM microscopy.

This work presents a comparison between three different High-overtone Bulk Acoustic Resonators based on different materials. Furthermore, the goal of this work is to realize a High-overtone Bulk Acoustic Resonators presented a temperature coefficient of frequency less than 10 ppm over a wide range of temperature around a turnover temperature, and a Q.f product higher than 5×10 13 Hz. After a discussion about the choice of materials to achieve such resonator and the description of our microfabrication, three High-overtone Bulk Acoustic Resonators based on a Lithium of Niobate, Quartz, Lithium of Tantalate, AlN and Sapphire materials are compared in term of the temperature coefficient of frequency, the Q.f product and the phase noise. The new HBAR exhibits a Q.f product around 3.7×10 13 Hz, a turnover around 55°C with a parabolic shape and a temperature coefficient of frequency around +/-4 ppm/K.

National audience; &nbsp

National audience; &nbsp