Papers by Natalya Naumenko
Journal of Applied Physics, Sep 14, 2014
Plate modes in LiTaO<inf>3</inf> for application in wide band resonator filters with improved temperature characteristics
Rigorous analysis of plate modes propagating in LiTaO3 plates was performed using the numerical t... more Rigorous analysis of plate modes propagating in LiTaO3 plates was performed using the numerical technique SDA-FEM-SDA. The characteristics of zero- and first-order plate modes were calculated in rotated YX cuts of LT as functions of cut angle and plate thickness. Orientations providing high electromechanical coupling (up to 19%), zero TCF at resonance and high velocities (up to 19,000 m/s) were found and investigated. The wave motions following the propagation of some modes are visualized. The possibility of enhancement of some modes by deposition of metal film on the plate bottom surface and the sensitivity of higher-order modes to variation of plate thickness are discussed.
Spurious Modes in Laterally Excited Bulk Acoustic Resonators (XBARs): Analysis and Suppression
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, Jun 1, 2023
Two-dimensional acousto-optic SLM
Acousto-optic two-dimensional modulators based on monoclinic KYW crystal
2022 International Conference Laser Optics (ICLO), Jun 20, 2022
Optimal design for an innovative very-high-temperature hybrid SAW sensor
Surface Acoustic Wave sensors are a promising enabling technology to achieve temperature monitori... more Surface Acoustic Wave sensors are a promising enabling technology to achieve temperature monitoring in extreme conditions, and especially at very high temperature, above 900°C. Applications in the air and space, chemical, steel, and automotive industries are notably expected. Although many of the technical challenges posed by the development of these sensors have been tackled and solved over the years, there is still no SAW sensor able to withstand very high temperatures for a long time on the market (yet). A possible alternative could be to combine a SAW transponder with a thermocouple ('SAW Hybrid'). The thermocouple would be read wirelessly using a SAW transponder, itself located at a place nearby where the temperature doesn't exceed 350°C. The feasibility of this concept was recently demonstrated, using a 400MHz device. However, the obtained sensitivity was very low, and an optimized Design is needed, to increase it. It is notably expected that a higher operating frequency will significantly improve the sensitivity. In this paper, we present an optimal Design of the SAW Hybrid AlN/LN multilayered structure, for operation at 2.45GHz, with buried Pt electrodes.
Theoretical and experimental investigation of spurious modes in a SAW delay line based on langasite
The measured characteristics of a test SAW device built on YX cut of LGS were analyzed in the tim... more The measured characteristics of a test SAW device built on YX cut of LGS were analyzed in the time-frequency domain, using spectrogram representation. Especially, spurious modes were detected and investigated. A combination of numerical techniques was applied to the analysis of the observed spurious modes, including simulation of the admittance of a Pt grating on an LGS plate of finite thickness and visualization of the wave structure at different frequencies. The influence of the anisotropy on the frequency-time ratio was taken into account for each of three obliquely propagating bulk waves via detailed numerical investigation of the BAW slowness surface. The main spurious BAW modes propagating parallel to the surface or at certain tilt angles and reflected from the bottom were identified. The frequency-time dependences predicted via analysis of BAW anisotropy showed good agreement with experimental results.
Acousto-optic spatial light modulator (SLM) based on KYW crystal
We designed a new configuration of acousto-optic spatial light modulator based on biaxial crystal... more We designed a new configuration of acousto-optic spatial light modulator based on biaxial crystal KY(WO4)2 (KYW). This material has proved to be a good candidate to fill the gap between paratellurite having high acousto- optic efficiency and quartz having low efficiency but high laser-induced damage threshold. The modulator uses isotropic diffraction by a slow quasi-shear bulk acoustic wave propagating in the autocollimation direction. This ensures good compromise between acousto-optic figure of merit, which is only 30% less than in z-cut longitudinal- wave paratellurite, and high laser-induced damage threshold. The prototype modulator has the spatial resolution of 250 with the central frequency of 100 MHz and the aperture of 20 mm. The designed spatial light modulator is aimed at high-power ultrashort laser pulse shaping applications in near and middle infrared.
Spurious Modes in Laterally Excited Bulk Acoustic Resonators (XBARs): Analysis and Suppression
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Materials, Nov 17, 2022
Monoclinic potassium rare-earth crystals are known as efficient materials for solid-state lasers ... more Monoclinic potassium rare-earth crystals are known as efficient materials for solid-state lasers and acousto-optic modulators. A number of specific configurations for acousto-optic devices based on those crystals have recently been proposed, but the acousto-optic effect of those crystals has only been analyzed fragmentarily for some interaction directions. In this work, we numerically searched for the global maxima of an acousto-optic figure of merit for isotropic diffraction in KGd(WO 4 ) 2 and KY(WO 4 ) 2 crystals. It was demonstrated that the global maxima of the acousto-optic figure of merit in those crystals occur in the slow optical mode propagating along the crystal's twofold symmetry axis and in the acoustic wave propagating orthogonally, both for quasi-longitudinal and quasi-shear acoustic modes. The proposed calculation method can be readily used for the optimization of the acousto-optic interaction geometry in crystals with arbitrary symmetry.
InTech eBooks, Nov 14, 2011
Since 70-ies, when the first delay lines and filters employing surface acoustic waves (SAW) were ... more Since 70-ies, when the first delay lines and filters employing surface acoustic waves (SAW) were designed and fabricated, the use of SAW devices in special and commercial applications has expanded rapidly and the range of their working parameters was extended significantly (Hashimoto, 2000; Ruppel, 2001, 2002). In the last decade, their wide application in communication systems, cellular phones and base stations, wireless temperature and gas sensors has placed new requirements to SAW devices, such as very high operating frequencies (up to 10 GHz), low insertion loss, about 1 dB, high power durability, stable parameters at high temperatures etc. The main element of a SAW device is a piezoelectric substrate with an interdigital transducer (IDT) used for generation and detection of SAW in the substrate. The number of single crystals utilized as substrates in SAW devices did not increase substantially since 70ies because a new material must satisfy the list of strict requirements to be applied in commercial SAW devices: sufficiently strong piezoelectric effect, low or moderate variation of SAW velocity with temperature, low cost of as-grown large size crystals for fabrication of 4-inch wafers, long-term power durability, well developed and non-expensive fabrication process for SAW devices etc. Today only few single crystals are utilized as substrates in SAW devices: lithium niobate, LiNbO 3 (LN), lithium tantalate, LiTaO 3 (LT), quartz, SiO 2 , lithium tetraborate, Li 2 B 4 O 7 (LBO), langasite, La 3 Ga 5 SiO 14 (LGS) and some crystals of LGS group (LGT, LGN etc.) with similar properties. The SAW velocities in these single crystals do not exceed 4000 m/s, which limit the highest operating frequencies of SAW devices by 2.5-3 GHz because of limitations imposed by the line-resolution technology of IDT fabrication. The minimum achievable insertion loss and maximum bandwidth of SAW devices depend on the electromechanical coupling coefficient, which can be evaluated for SAW as k 2 ≈2ΔV/V, where ΔV is the difference between SAW velocities on free and electrically shorted surfaces. The largest values of k 2 can be obtained in some orientations of LN and LT. Ferroelectric properties of these materials are responsible for a strong piezoelectric effect. As a result, k 2 reaches 5.7% in LN and 1.2% in LT, for SAW. For leaky SAW (LSAW) propagating in rotated Y-cuts of both crystals, the coupling is higher and can exceed 20% for LN and 5% for LT. However, LSAW attenuates because of its leakage into the bulk waves when it propagates along the crystal surface. As a www.intechopen.com Acoustic Waves-From Microdevices to Helioseismology 422 result, insertion loss of a SAW device increases. Attenuation coefficient depends on a crystal cut and IDT geometry. For example, in 36º to 48º rotated YX cuts of LT and in 41º to 76º YX rotated YX cuts of LN, high electromechanical coupling of LSAW can be combined with low attenuation coefficient via simultaneous optimization of orientation and electrode structure (Naumenko & Abbott, US patents, 2003, 2004). When these substrates are utilized in radiofrequency (RF) SAW filters with resonator-type structures, low insertion loss of 1dB or even less can be obtained. Today such low loss filters are widely used in mobile communication and navigation systems. The main drawback of these devices is high sensitivity of the characteristics to variations of temperature because the typical values of temperature coefficient of frequency (TCF) vary between-30 ppm/ºC and-40 ppm/ºC for LT and between-60 ppm/ºC and-75 ppm/ºC for LN. Contrary to LN and LT, quartz is characterized by excellent temperature stability of SAW characteristics but low electromechanical coupling coefficient, k 2 <0.15%. Hence, even in resonator-type SAW filters with very narrow bandwidths, about 0.05%, where the loss of radiated energy is minimized due to the energy storage in a resonator, the best insertion loss achieved in a SAW device with matching circuits is only 2.5-4 dB. In some orientations of LBO, LGS and other crystals of LGS group, zero TCF is combined with a moderate electromechanical coupling coefficient. However, these crystals have limited applications in commercial SAW devices because low SAW velocities restrict highfrequency applications on LGS and LBO dissolves in water and acid solutions, which prohibits application of conventional wafer fabrication processes to this material and finally results in an increased cost of SAW devices. Hence, none of available single crystalline materials provides a combination of large piezoelectric coupling, zero TCF and high propagation velocity. A strong need in such material exists today, especially for application in SAW duplexers and multi-standard cellular phones, where the temperature compensation is the key issue because of necessity to divide a limited frequency bandwidth into few channels with no overlapping allowed in a wide range of operating temperatures. As an alternative to conventional SAW substrates, layered or multilayered (stratified) materials were studied extensively since 80-ies but only in the last decade some of these structures found commercial applications in SAW devices, due to the recent successes of thin film deposition technologies and development of robust simulation tools for design of SAW devices on layered structures.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, Sep 1, 2014
Dispersion of Lamb waves propagating in AlN plates with a periodic Al grating on the top surface ... more Dispersion of Lamb waves propagating in AlN plates with a periodic Al grating on the top surface and an Al electrode on the bottom surface is investigated using the numerical technique SDA-FEM-SDA, which combines finite element modeling (FEM) analysis of the electrode region with spectral-domain analysis (SDA) of the adjacent multi-layered half-spaces. Characteristics of zero-order and higher-order Lamb waves are presented as functions of plate thickness and spectral frequency, which varies in the first Brillouin zone. The structures of typical Lamb waves are examined via visualization of the instantaneous displacement fields in the AlN plate confined between the grating and the bottom electrode. The mechanism of building hybrid modes, which arise from intermode coupling between the counter-propagating Lamb waves of different symmetry and order, is illustrated by two examples of modes propagating with wavelengths λ = 3p and λ = 4p, where p is the pitch of the grating.
Analysis of interaction between two SAW modes in Pt grating on langasite cut (0°, 138.5°, 26.6°)
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, Nov 1, 2011
The numerical technique based on a previously developed rational approximation of harmonic admitt... more The numerical technique based on a previously developed rational approximation of harmonic admittance of a periodic grating was applied to analysis of SAW behavior in platinum grating on langasite cut with Euler angles (0°, 138.5°, 26.6°). The approximation is able to take into account interaction between surface and bulk waves or between two SAW modes. SAW dispersion was calculated at different values of electrode thickness varying between 1% and 4% of wavelength. It was found that with increasing Pt thickness, SAW behavior in the grating is strongly affected by interaction between two SAW modes propagating in the same orientation. An additional stopband, which results from this interaction, occurs at certain detuning from synchronous reflection condition and can cause spurious resonances of the admittance function. Interaction between two SAW modes is also responsible for anomalously slow growth of reflectivity with increasing platinum thickness.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, Sep 1, 2020
Fig. 1. ConTour shows a multitude of heterogeneous data items in several columns in the relations... more Fig. 1. ConTour shows a multitude of heterogeneous data items in several columns in the relationship view (bottom). The detail views display a selected pathway and selected chemical structures of compounds (top).
High-velocity surface acoustic waves in diamond and sapphire with zinc oxide film
Applied Physics Letters, Nov 8, 1999
We report two numerical examples of high-velocity surface acoustic waves, a type of surface waves... more We report two numerical examples of high-velocity surface acoustic waves, a type of surface waves which was recently shown to exist if a thin film is present on a surface. The nonattenuated high-velocity surface waves have been found in diamond orientation with Euler angles (0°,0°,45°) and sapphire orientation with Euler angles (0°,−20.3°,0°), with zinc oxide film. In diamond, the wave has “symmetric” structure with displacement in the symmetry plane while, in sapphire, the example of a “nonsymmetric” solution is presented. The numerical analysis has confirmed that, in both examples, the wave has a true surface nature, with one-partial structure in a substrate.
Symmetry Aspects in the Use of Multilayered Substrates for SAW Devices
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, 2022
Multilayered structures extensively studied as a novel type of substrates for surface acoustic wa... more Multilayered structures extensively studied as a novel type of substrates for surface acoustic wave (SAW) devices are characterized by an asymmetry of wave propagation: acoustic wave characteristics generally change with inversion of propagation direction or interchange of top/bottom surfaces in one of the layers, though separately each material is symmetric for such inversions. In this paper, the matrix formalism known as an effective tool for theoretical and numerical investigation of acoustic wave propagation in multilayered structures is applied to explain the existence of asymmetry and analyze its relation to the symmetry and orientations of combined materials. This phenomenon is illustrated by examples of layered structures combining LiTaO3 (LT) plate with quartz or Si, previously reported as potential substrates for SAW devices with improved performance. Asymmetry arises from anisotropy of combined materials and occurs even when one of these materials is non-piezoelectric. It was estimated numerically as a variation of SAW resonator characteristics with substrate or plate inversion and was analyzed as a function of plate or substrate orientation. In particular, it was shown that 'polarity inverted' structure enabling alternative resonator performance for the same material layers can be obtained either by an interchange of top/bottom surfaces of a piezoelectric plate or by inversion of propagation direction in a substrate. Asymmetry decreases with the introduction of an isotropic layer at the plate-substrate interface.
THE ANOMALOUS ELASTIC ANISOTROPY OF LiZB407 AND ITS INFLUENCE ON SAW PROPERTIES
The anomalous elastic anisotropy of Li2B407 caused by the “incorrect” relation between two elasti... more The anomalous elastic anisotropy of Li2B407 caused by the “incorrect” relation between two elastic modula, c33 and c44, is proved to be responsible for the existence of earlier found undamped longitudinal horizontally polarized (LH) type leaky waves. A simple proof is presented to show that “ray-polarized” quasilongitudinal bulk wave propagating in the plane of reflectional symmetry satisfies the stress-free conditions when the boundary plane is parallel to polarization vector and orthogonal to the plane of reflectional symmetry. The close relation between the particular directions, such as acoustic axes, and the existence of “non-leaky” waves is analyzed using the “exceptional wave line” method. LH type leaky waves exist in crystal cuts with Euler angles ((p,e,90), where cp is arbitrary when 8=40 ... 46”. If y45” the permitted interval of 8 angle is the largest: 8=35-68”.
Selection of materials for multilayered structures to be used in packageless sensors
Recently a multilayered structure with a low-velocity layer sandwiched between two high-velocity ... more Recently a multilayered structure with a low-velocity layer sandwiched between two high-velocity materials, one of which also works as a supporting substrate and another one as a coat isolating the wave from the influence of undesired external factors, was suggested for application in packageless sensors [1,2]. The thickness of a middle piezoelectric layer must be sufficient to confine the wave within this layer. The suggested combinations of materials included ZnO or GaN as a waveguiding layer, sapphire or diamond as a supporting substrate and Al2O3 (alumina) or AlN as a coating. In the present work, two previously reported structures were analyzed and compared to find the selection criterion for optimal combination of materials enabling high coupling of the useful mode and suppression of parasitic modes.
On the excitation of surface and pseudo-surface quasi-bulk waves
An investigation is made of the specific features of the excitation of (pseudo) quasi bulk surfac... more An investigation is made of the specific features of the excitation of (pseudo) quasi bulk surface waves. Particular attention is focused on the analysis of wave fields associated with “non-physical” plane wave solutions. As illustrations, numerical computations have been performed for SH-waves and quasi-longitudinal leaky waves in quartz
LiNbO<sub>3</sub> Plate Bonded to Quartz as a Substrate for High Frequency Wideband SAW Devices
Bonded wafers combining a thin LiNbO3 plate with a quartz substrate were studied numerically as p... more Bonded wafers combining a thin LiNbO3 plate with a quartz substrate were studied numerically as potential substrate materials for high frequency wideband SAW devices. Longitudinal leaky waves propagating with velocities up to 7000 m/s were investigated, and the multilayered structure was optimized to combine high velocity, high electromechanical coupling and negligible propagation losses. In the optimized structures non-attenuated waves can propagate with velocities V=5500-6200 m/s and coupling up to 18%. Examples of simulated admittances of SAW resonators demonstrate that in some optimal LiNbO3/quartz structures high quality factors Q>5000 can be achieved simultaneously at resonant and antiresonant frequencies if duty factor of electrode structure varies between 0.48 and 0.65. Due to sufficiently large optimal plate and electrode thicknesses, 40% and 5% of a wavelength, respectively, the found structures can be employed in SAW resonators operating at high frequencies, up to 5 GHz.
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Papers by Natalya Naumenko