Low-Loss Unidirectional Acoustic Focusing Transducer in Thin-Film Lithium Niobate

Abstract

In this work, we present gigahertz low-loss unidirectional acoustic focusing transducers in thin-film lithium niobate. The design follows the anisotropy of fundamental symmetric (S0) waves in X-cut lithium niobate. The implemented acoustic delay line testbed consisting of a pair of the proposed transducers shows a low insertion loss of 4.2 dB and a wide fractional bandwidth of 7.5% at 1 GHz. The extracted transducer loss is 1.46 dB, and the propagation loss of S0 waves is 0.0126 dB/μm. The design framework is readily extendable to other acoustic modes, given consideration on the optimal orientation for power flow and electromechanical transduction.

Non-reciprocal acoustoelectric microwave amplifiers with net gain and low noise in continuous operation

“…For example, reducing the doping concentration to N d = 5 × 10 15 cm −3 could increase the demonstrated gain slope by sixfold. Further reduction in the semiconductor amplifier width, especially when combined with acoustic guiding [28][29][30][31] or focusing 23,32,33 methods, could also reduce the dissipated power and improve the overall device thermal stability. These developments should also improve the noise figure, as our acoustic noise figure is currently limited by the onset of thermal instability.…”

RF acoustic microsystems based on suspended lithium niobate thin films: advances and outlook

“…If neglected, the skew propagation of acoustic waves could lead to additional IL in ADLs [82] and introduce Q degradation or spurious modes in resonators [125]. Elsewhere, it may cause reduced intensity for wave focusing devices [126].…”

“…In addition to potential non-zero PFA issues, one can also leverage it to build more complex in-plane structures (figure 13). One example is the wave focusing transducers [126]. Incorporating PFA considerations in the curved transducers can significantly increase the acoustic wave intensity for interacting with other physics.…”