Parametric resonator and filter using the same

1. A resonator, comprising:

a vibrator that performs mechanical vibration;

an exciting unit that applies an exciting force to the vibrator; and

a modulating unit configured to cyclically vary a spring property of the vibrator according to a cycle of the exciting force,

wherein the vibrator vibrates when the exciting force is applied to the vibrator from the exciting unit.

2. The resonator according to claim 1 , wherein the modulating unit is configured to vary the spring property of the vibrator so as to increase a vibration amplitude of the vibrator.

3. The resonator according to claim 2 , wherein a modulation frequency of the spring property of the vibrator is the same as a frequency of the exciting force from the exciting unit.

4. A resonator, comprising:

a vibrator that performs mechanical vibration;

an exciting unit that applies an exciting force to the vibrator; and

a modulating unit configured to modulate a spring property of the vibrator according to a cycle of the exciting force from the exciting unit,

wherein the vibrator vibrates when the exciting force is applied to the vibrator from the exciting unit;

wherein a modulation frequency of the spring property of the vibrator is the same as a frequency of the exciting force from the exciting unit;

wherein the exciting unit applies the exciting force to the vibrator such that a cyclic exciting force from the exciting unit has a value proportional to sin ωt;

wherein the modulating unit modulates the spring property such that an increment of the spring property is in proportion to cos(ωt+φ); and

wherein a phase φ is in a range of −22.5° to 112.5° or a range of 25 157.5° to 292.5°.

5. The resonator according to claim 4 , wherein the phase φ is approximately 45° or 225°.

6. The resonator according to claim 1 , wherein a modulation frequency of the spring property of the vibrator is two times as much as a frequency of the exciting force from the exciting unit.

7. A resonator, comprising:

a vibrator that performs mechanical vibration;

an exciting unit that applies an exciting force to the vibrator; and

a modulating unit configured to modulate a spring property of the vibrator according to the exciting force,

wherein the vibrator vibrates when the exciting force is applied to the vibrator from the exciting unit;

wherein a modulation frequency of the spring property of the vibrator is two times as much as a frequency of the exciting force from the exciting unit;

wherein the exciting unit applies the exciting force to the vibrator such that a cyclic exciting force from the exciting unit has a value proportional to sin ωt;

wherein the modulating unit modulates the spring property such that an increment of the spring property is in proportion to cos(2ωt+φ); and

wherein a phase φ is in a range of −225° to 45°.

8. The resonator according to claim 7 , wherein the phase φ is approximately −90°.

9. The resonator according to claim 6 , wherein, in a case where in the exciting unit, a cyclic exciting force has a value proportional to sin ωt and a resonance angular frequency of when the spring property is not modulated is ω 0 , the modulating unit modulates the spring property such that an increment of the spring property is in proportion to cos 2ω(t−D), and a delay time D is in a range of 0 to 0.625 times as large as 2π/(2ω 0 ) or in a range of 0.875 to 1 times as large 25 as 2π/(2ω 0 ).

10. The resonator according to claim 9 , wherein the delay time D is approximately 0.25 times as large as 2π/(2ω 0 ).

11. The resonator according to claim 1 , wherein the exciting unit is an electrode which is located near the vibrator and converts a variation in voltage between the vibrator and the electrode into the exciting force applied to the vibrator.

12. A resonator, comprising:

a vibrator that performs mechanical vibration;

an exciting unit that applies an exciting force to the vibrator; and

a modulating unit that modulates a spring property of the vibrator,

wherein the vibrator vibrates when the exciting force is applied to the vibrator from the exciting unit;

wherein the modulating unit modulates the vibrator according to the exciting force; and

wherein the modulating unit includes a temperature control unit which controls a temperature of the vibrator, and the modulating unit modulates the spring property according to a variation in the temperature of the vibrator.

13. The resonator according to claim 12 , wherein the temperature control unit generates the time variation in the temperature of the vibrator according to light radiation from a light radiating unit.

14. The resonator according to claim 12 , wherein the temperature control unit includes a current control unit which controls an amount of current supplied to the vibrator, and controls the temperature of the vibrator using Joule heat.

15. The resonator according to claim 12 , wherein the vibrator has fixed portions or supporting portions at two locations or more, and uses peripheral portions of the fixed portions or the supporting portions as vibration nodes.

16. The resonator according to claim 15 , wherein the vibrator is a both-end supported beam.

17. The resonator according to claim 13 , wherein the light radiating unit includes a light source and a mirror and is configured such that light emitted from the light source passes through the vibrator, is reflected on the mirror, and is incident on the vibrator.

18. The resonator according to claim 17 , wherein the light radiating unit includes:

a laser diode which is provided at one end of the vibrator; and

a mirror which is provided at the other end thereof; and

wherein the light radiating unit radiates a laser beam from the one end of the vibrator to the other end thereof in a longitudinal direction of the vibrator and performs an optical pumping.

19. The resonator according to claim 18 , wherein the vibrator is configured such that peripheral portions of the vibrator other than both ends thereof are surrounded by a region where a refractive index is smaller than a refractive index of the vibrator.

20. The resonator according to claim 17 , wherein the vibrator has both ends where source and drain regions are formed, the longitudinal direction of the vibrator is used as a channel, a gate electrode is formed at a predetermined gap from the channel, and the gate electrode is made of a metal or a polycide metal to forms a reflective surface.

21. The resonator according to claim 1 , wherein at least the vibrator is sealed in a vacuum.

22. A filter using the resonator according to claim 1 .