CPC B01L 3/502715 (2013.01) [B01L 3/50273 (2013.01); B01L 3/502761 (2013.01); G01N 15/1404 (2013.01); G02B 21/32 (2013.01); H03H 9/14505 (2013.01); B01L 2200/0668 (2013.01); B01L 2400/0436 (2013.01); G01N 2015/142 (2013.01)] | 12 Claims |
1. An electroacoustic device comprising a transducer comprising a piezoelectric substrate, first and second electrodes of inverse polarity comprising respective first and second tracks provided on said substrate, the first and second tracks spiraling around a same center, the transducer being configured for generating a swirling ultrasonic surface wave in the substrate, wherein each of the first and second tracks spirals along a line defined by the equation
wherein:
R(θ) is the polar coordinate of the line with respect with the azimuthal angle θ,
φ0 is a free parameter,
l is the vortex order of a swirling SAW of pulsation ω, l being an integer such that |l|≥1.
μ0(θ) is given by:
where zi−zi-1 is the distance between two successive interfaces separating materials stacked onto the substrate, z0 being the height of the interface between the substrate and the layer contacting the substrate, μ0(θ)=0 in case of the absence of stacked layers
where ψ depends on Θ as follows:
sr(ψ) is the wave slowness on the surface plane of the substrate in the direction of propagation ψ, and sz(ψ) is the wave slowness in the out of plane direction, a wave slowness in a direction i being r or z being computed from the wavenumber ki as sr(ψ)=kr(ψ)/ω: and sz(ψ)=kz(ψ)/ω
sr′(ψ) is the derivative of sr(ψ) in respect to the direction of propagation,
α(ψ) is the phase of the vertical motion of the wave propagating in direction ψ versus the associated electric field.
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