Apparatus, systems, and methods of acoustic energy confinement with phononic crystals

Patent metadata

Field	Value
Publication number	US-10084426-B2
Application number	US-201715695523-A
Country	US
Kind code	B2
Filing date	Sep 5, 2017
Priority date	Dec 15, 2015
Publication date	Sep 25, 2018
Grant date	Sep 25, 2018

Abstract

An acoustic resonator includes a wafer and a first phononic crystal disposed on the wafer to define an acoustic waveguide so as to propagate an acoustic wave along a propagation direction. The first phononic crystal includes a first two-dimensional (2D) array of metal stripes having a first period on the propagation direction. The apparatus also includes a second phononic crystal and a third phononic crystal disposed on two sides of the first phononic crystal and having a different period from the first period. The second phononic crystal and the wafer define a first reflector to reflect the acoustic wave. The third phononic crystal and the wafer define a second reflector to reflect the acoustic wave.

First claim

The invention claimed is:

1. An apparatus for confining an acoustic wave, the apparatus comprising:
a wafer;
a first phononic crystal disposed on the wafer, the first phononic crystal and the wafer defining an acoustic waveguide to propagate the acoustic wave along a propagation direction, the first phononic crystal comprising a first two-dimensional (2D) array of metal stripes having a first period along the propagation direction;
a second phononic crystal disposed on a first side of the first phononic crystal, the second phononic crystal comprising a second 2D array of metal stripes having a second period, different than the first period, along the propagation direction, the second phononic crystal and the wafer defining a first reflector to reflect the acoustic wave; and
a third phononic crystal disposed on a second side, opposite the first side, of the first phononic crystal, the third phononic crystal comprising a third 2D array of metal stripes having a third period, different than the first period, along the propagation direction, the third phononic crystal and the wafer defining a second reflector to reflect the acoustic wave,
wherein the second period is different than the third period.

2. The apparatus of claim 1 , wherein the wafer comprises silicon.

3. The apparatus of claim 1 , wherein the first 2D array of metal stripes comprises at least one of copper or tungsten.

4. The apparatus of claim 1 , wherein the first period is about 10 nm to about 1 μm.

5. An apparatus for confining an acoustic wave, the apparatus comprising:
a wafer;
a first phononic crystal disposed on the wafer, the first phononic crystal and the wafer defining an acoustic waveguide to propagate the acoustic wave along a propagation direction, the first phononic crystal comprising a first two-dimensional (2D) array of metal stripes having a first period along the propagation direction;
a second phononic crystal disposed on a first side of the first phononic crystal, the second phononic crystal comprising a second 2D array of metal stripes having a second period, different than the first period, along the propagation direction, the second phononic crystal and the wafer defining a first reflector to reflect the acoustic wave; and
a third phononic crystal disposed on a second side, opposite the first side, of the first phononic crystal, the third phononic crystal comprising a third 2D array of metal stripes having a third period, different than the first period, along the propagation direction, the third phononic crystal and the wafer defining a second reflector to reflect the acoustic wave,
wherein the second period is more than 10% greater than the first period.

6. The apparatus of claim 1 , wherein the second period is substantially equal to the third period.

7. The apparatus of claim 1 , further comprising:
at least one acoustic transducer, disposed between the first phononic crystal and the wafer, to convert an electrical signal into the acoustic wave.

8. The apparatus of claim 7 , wherein the at least one acoustic transducer comprises at least one field-effect transistor (FET).

9. The apparatus of claim 7 , wherein the at least one acoustic transducer comprises an array of acoustic transducers, having a transducer period substantially equal to the first period, disposed along the propagation direction, wherein adjacent acoustic transducers in the array of acoustic transducers are configured to generate acoustic signals having opposite phases.

10. The apparatus of claim 1 , further comprising:
a sensing transducer, disposed between the first phononic crystal and the wafer, to convert the acoustic wave into at least one electrical signal.

11. The apparatus of claim 10 , wherein the sensing transducer comprises an FET.

12. The apparatus of claim 1 , further comprising:
a fourth array of 2D metal stripes disposed between the first 2D array of metal stripes and the second 2D array of metal stripe, at least one spacing between adjacent metal stripes in the fourth array of metal stripes is greater than the first period and less than the second period.

13. The apparatus of claim 1 , further comprising:
a fourth array of 2D metal stripes disposed between the first 2D array of metal stripes and the second 2D array of metal stripes, wherein respective spacings between adjacent metal stripes change progressively from the first period to the second period along the propagation direction.

14. A method of confining an acoustic wave, the method comprising:
guiding the acoustic wave along a propagation direction in a waveguide defined by a wafer and a first phononic crystal disposed on the wafer, the first phononic crystal comprising a first two-dimensional (2D) array of metal stripes having a first period along the propagation direction;
reflecting the acoustic wave by a first reflector defined by the wafer and a second phononic crystal disposed on a first side of the first phononic crystal, the second phononic crystal comprising a second 2D array of metal stripes having a second period, different than the first period, along the propagation direction; and
reflecting the acoustic by a second reflector defined by the wafer and a third phononic crystal disposed on a second side, opposite the first side, of the first photonic crystal, the third phononic crystal comprising a third 2D array of metal stripes having a third period, different than the first period, along the propagation direction; and
generating the acoustic wave using an array of acoustic transducers, having a transducer period substantially equal to the first period, disposed along the propagation direction, wherein adjacent acoustic transducers in the array of acoustic transducers are configured to generate acoustic signals having opposite phases.

15. The method of claim 14 , wherein generating the acoustic wave comprises generating the acoustic wave using at least one field-effect transistor (FET) disposed between the first photonic crystal and the wafer.

16. The method of claim 14 , wherein generating the acoustic wave comprises generating the acoustic wave having a wave vector along the propagation direction k x substantially equal to π/a, where a is the first period of the first 2D array of metal stripes.

17. The method of claim 14 , further comprising:
converting the acoustic wave into at least one electrical signal using a sensing transducer, disposed between the first phononic crystal and the wafer.

18. The method of claim 17 , wherein converting the acoustic wave comprises transmitting the acoustic wave into an FET.

19. The method of claim 14 , further comprising:
propagating the acoustic wave through a transition region defined by the wafer and a fourth array of 2D metal stripes disposed between the first 2D array of metal stripes and the second 2D array of metal stripes so as to reduce scattering of the acoustic wave, at least one spacing between adjacent metal stripes in the fourth array of metal stripes is greater than the first period and less than the second period.

20. The method of claim 14 , further comprising:
propagating the acoustic wave through a transition region defined by the wafer and a fourth array of 2D metal stripes disposed between the first 2D array of metal stripes and the second 2D array of metal stripes so as to reduce scattering of the acoustic wave, wherein spacing between adjacent metal stripes changes progressively from the first period to the second period along the propagation direction.

21. An acoustic reso

Assignees

• Massachusetts Inst Technology

Inventors

• Bahr Bichoy W
• Weinstein Dana

Classifications

• H01P3/08

  Microstrips; Strip lines · CPC title

• H01L41/09

  Electricity · mapped topic

• H03H9/17

  having a single resonator (crystal tuning forks H03H9/21) · CPC title

• H03H9/02244 Primary

  of microelectro-mechanical resonators · CPC title

• H03H9/2405 Primary

  of microelectro-mechanical resonators · CPC title