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Cryogenic piezoelectric effects in thin film strontium titanate devices

Ahmed Khalil, Anja Ulrich, Kamal Brahim, Andries Boelen, Danut-Valentin Dinu, Halil Cuma, Ioannis Petrides, Sandeep Seema Saseendran, Xavier Rottenberg, Pol Van Dorpe, Kristiaan De Greve, Oskar Painter, Clement Merckling, Frédéric Peyskens, Christian Haffner

Abstract

Next generation quantum technologies will need to rely on efficient transduction between electrical, optical, and mechanical quantum degrees of freedom to generate large-scale entanglement over large distances. The performance of such transducers is fundamentally limited by the cryogenic properties of the underlying materials. Here, we demonstrate that engineering strain in ferroelectric thin-film strontium titanate ($\mathrm{SrTiO_3}$) not only results in an exceptionally large Pockels coefficient, but also in a robust linear piezoelectric response at cryogenic temperatures, surpassing previous thin-film benchmarks. We measure piezoelectric tensor elements of $d_{15} = 151.8 \pm 1.5$ pm/V and $d_{33} = 54.8 \pm 4$ pm/V, and an effective photoelastic coefficient of $p_{\mathrm{eff}}$ = 0.56 at 5~K. Utilizing these enhanced properties, we demonstrate the first $\mathrm{SrTiO_3}$-on-oxide acousto-optic modulator with a voltage-length product ($V_πL$) of $0.874 \pm 0.084$ V.cm, outperforming state-of-the-art unreleased modulators that typically feature a $V_πL$ of a few V.cm. Our results establish thin-film $\mathrm{SrTiO_3}$ as a promising material system for integrated quantum photonics operating at cryogenic temperatures.

Cryogenic piezoelectric effects in thin film strontium titanate devices

Abstract

Next generation quantum technologies will need to rely on efficient transduction between electrical, optical, and mechanical quantum degrees of freedom to generate large-scale entanglement over large distances. The performance of such transducers is fundamentally limited by the cryogenic properties of the underlying materials. Here, we demonstrate that engineering strain in ferroelectric thin-film strontium titanate () not only results in an exceptionally large Pockels coefficient, but also in a robust linear piezoelectric response at cryogenic temperatures, surpassing previous thin-film benchmarks. We measure piezoelectric tensor elements of pm/V and pm/V, and an effective photoelastic coefficient of = 0.56 at 5~K. Utilizing these enhanced properties, we demonstrate the first -on-oxide acousto-optic modulator with a voltage-length product () of V.cm, outperforming state-of-the-art unreleased modulators that typically feature a of a few V.cm. Our results establish thin-film as a promising material system for integrated quantum photonics operating at cryogenic temperatures.
Paper Structure (15 sections, 50 equations, 9 figures, 2 tables)

This paper contains 15 sections, 50 equations, 9 figures, 2 tables.

Table of Contents

  1. Piezoelectricity extraction
  2. Electrical characterization and impedance extraction
  3. Mason model and electromechanical coupling
  4. $e_{15}$ extraction based on BAW
  5. Acoustic wave excitation dependency on piezoelectric tensor
  6. Single domain piezoelectric coefficient of twin-domain structure
  7. Acoustic propagation losses
  8. Acousto-optic modulation
  9. Calculating the $V_\pi L$
  10. Photoelasticity
  11. Moving boundary contribution
  12. Photoelastic contribution
  13. Effective photoelastic coefficient of SrTiO$_3$
  14. Optical response with increased RF power
  15. Materials overview

Figures (9)

  • Figure 1: Microscope image of a representative IDT fabricated on a SrTiO$_3$ thin film.
  • Figure 2: a) Mason equivalent circuit model for the IDT electromechanical response. The typical measured resistance and wideband $\mathrm{Im}[Z]$ are shown in (b) and (c), respectively. (d) Shows the numerically simulated map from capacitance to SrTiO$_3$ permittivity.
  • Figure 3: Measured impedance for LFE IDT with $\Lambda = 8~\mu$m at 5K with $13\;V/\mu$m bias.
  • Figure 4: (a) Slowness curves for Rayleigh wave with and without piezoelectric coupling accounting only $e_{33}$ component. (b) Rayleigh wave electromechanical coupling for different piezoelectric tensor elements.
  • Figure 5: Simulated mode profiles with its corresponding driving domain for (a) Rayleigh wave and (b) Bulk shear wave.
  • ...and 4 more figures