Elastic wave device
An elastic wave device includes a first IDT electrode on a first main surface of a LiNbO 3 substrate, and a second IDT electrode on a second main surface thereof. The application of alternating voltages with reversed phases to each other to the first and second IDT electrodes excites plate waves in which SH waves in a high order mode predominate. The elastic wave device uses the plate waves in the high order mode in which the SH waves predominate.
1. An elastic wave device comprising:
a LiNbO 3 substrate including a first main surface and a second main surface on an opposite side of the first main surface;
a first IDT electrode provided on the first main surface of the LiNbO 3 substrate; and
a second IDT electrode provided on the second main surface of the LiNbO 3 substrate so as to be opposed to the first IDT electrode across the LiNbO 3 substrate; wherein
a plate wave in a high order mode in which an SH wave predominates is excited in the LiNbO 3 substrate as an elastic wave in response to alternating voltages of reversed phases to each other being applied to the first IDT electrode and the second IDT electrode.
2. The elastic wave device according to claim 1 , wherein in Euler angles (ϕ, θ, ψ) of the LiNbO 3 substrate, ϕ=0±5°, ψ=0±5°, and θ is about 72° or more and about 97° or less.
3. The elastic wave device according to claim 1 , wherein a thickness of the LiNbO 3 substrate is about 0.05λ or more and about 0.52λ or less, and λ represents a wavelength determined by a pitch of electrode fingers of the first and second IDT electrodes.
4. The elastic wave device according to claim 1 , wherein a duty of each of the first and second IDT electrodes is about 0.15 or more and about 0.77 or less.
5. The elastic wave device according to claim 1 , wherein the first and second IDT electrodes each include an electrode film made of Al or an alloy having Al as a main constituent, and a film thickness of each of the electrode films is about 0.035λ or less, and λ represents a wavelength determined by a pitch of electrode fingers of the first and second IDT electrodes.
6. The elastic wave device according to claim 1 , wherein a fractional bandwidth of the elastic wave device is 17% or more.
7. The elastic wave device according to claim 1 , wherein a fractional bandwidth of the elastic wave device is 20% or more.
8. An elastic wave device comprising:
a LiNbO 3 substrate including a first main surface and a second main surface on an opposite side of the first main surface;
an IDT electrode provided on the first main surface of the LiNbO 3 substrate; and
an electrode film provided on the second main surface of the LiNbO 3 substrate so as to occupy an entire area enclosed with outer edges of the IDT electrode in a plan view from a side of the first main surface; wherein
a plate wave in a high order mode in which an SH wave predominates is excited in the LiNbO 3 substrate as an elastic wave in response to an alternating voltage being applied to the IDT electrode.
9. The elastic wave device according to claim 8 , wherein in Euler angles (ϕ, θ, ψ) of the LiNbO 3 substrate, ϕ=0±5°, ψ=0±5°, and θ is about 68° or more and about 96° or less.
10. The elastic wave device according to claim 8 , wherein a thickness of the LiNbO 3 substrate is about 0.05λ or more and about 0.18λ or less, and λ represents a wavelength determined by a pitch of electrode fingers of the IDT electrode.
11. The elastic wave device according to claim 8 , wherein a duty of the IDT electrode is about 0.1 or more and about 0.68 or less.
12. The elastic wave device according to claim 8 , wherein the IDT electrode includes an electrode film made of Al or an alloy having Al as a main constituent, and a film thickness of the electrode film is about 0.022λ or less, and λ represents a wavelength determined by a pitch of electrode fingers of the IDT electrode.
13. The elastic wave device according to claim 8 , wherein the electrode film defines a floating electrode.
14. The elastic wave device according to claim 8 , wherein the electrode film is made of one of Ti, Au, Ni, Cr, and a conductive compound including one of ZnO and ITO.
15. The elastic wave device according to claim 8 , wherein a fractional bandwidth of the elastic wave device is 17% or more.
16. The elastic wave device according to claim 8 , wherein a fractional bandwidth of the elastic wave device is 20% or more.
17. The elastic wave device according to claim 8 , wherein a thickness of the LiNbO 3 substrate is about 0.07λ or more and about 0.16λ or less, and λ represents a wavelength determined by a pitch of electrode fingers of the IDT electrode.