High-frequency surface acoustic wave devices at very low temperature: Application to loss mechanisms evaluation

Abstract

Previous work on high-performance bulk wave resonators in the frequency range of 5 to 25 MHz has shown that, by cooling to liquid helium temperature, acoustic losses become negligible. Therefore other sources of losses can be precisely measured. A similar approach is followed in the present work for high-frequency surface wave resonators. Experiments have been performed at 416 MHz on quartz devices. It is shown that for surface waves propagating in a good surface acoustic wave ͑SAW͒ resonator an important source of acoustic loss is due to intrinsic acoustic losses. By cooling the device to below 30 K, the quality factor Q shows a T Ϫ4 dependence characteristic of intrinsic acoustic losses. Below 4-10 K a plateau region is reached. High Q values in the range of 1.5ϫ10 5 have been obtained at 4.2 K for 416-MHz devices, yielding a Qϫ f product of 7.5ϫ10 13 almost as good as for cooled bulk devices. Another set of measurements on a lithium niobate ͑LiNbO 3 ͒ resonator at 847 MHz does not give a significant increase of quality factor Q at low temperature. This is due to the presence of other loss mechanisms not related to intrinsic acoustic losses because the LiNbO 3 resonator operates in a leaky mode rather than a Rayleigh mode. The applications of the method to the characterization of new kinds of SAW resonators will be helpful for optimizing high-Q surface wave resonators at high frequencies, based on new modes or new materials.

Sub-optical wavelength acoustic wave modulation of integrated photonic resonators at microwave frequencies

“…An average value of 6 dB mm À 1 is obtained, which should be considered as an upper bound estimation of the propagation loss, because effects such as the reflection of the acoustic wave by the waveguide are not considered in the calculation. With this apparently high value of linear loss 35,36 , the total acoustic loss, however, is insignificant, considering that the footprint of photonic devices typically spans only a few tens of micrometres. Although the interference effect can be used to enhance A/O modulation at a specific frequency, the large passband ripples are undesirable for signal processing applications.…”

Universal Quantum Transducers Based on Surface Acoustic Waves

“…Q m refers to losses due to interaction with thermal phonons, losses due to defects in the material, and propagation losses due to contamination [37,38]. These losses ultimately limit Q: Low-temperature experiments on quartz have demonstrated SAW resonators with Q m × f½GHz > 10 5 [22,23]. Another source of losses is due to mode conversion into bulk modes.…”

“…(3) Our scheme is built upon an established technology [14,15]: Lithographic fabrication techniques provide almost arbitrary geometries with high precision as evidenced by a large range of SAW devices such as delay lines, bandpass filters, resonators, etc. In particular, the essential building blocks needed to interface qubits with SAW phonons have already been fabricated, according to design principles familiar from electromagnetic devices: (i) SAW resonators, the mechanical equivalents of Fabry-Perot cavities, with low-temperature measurements reaching quality factors of Q ∼ 10 5 even at gigahertz frequencies [22][23][24], and (ii) acoustic waveguides as analog to optical fibers [14]. (4) For a given frequency in the gigahertz range, due to the slow speed of sound of ∼10 3 m=s for typical materials, device dimensions are in the micrometer range, which is convenient for fabrication and integration with semiconductor components, and about 10 5 times smaller than corresponding electromagnetic resonators.…”

Universal Quantum Transducers Based on Surface Acoustic Waves

“…Q m refers to losses due to interaction with thermal phonons, losses due to defects in the material and propagation losses due to contamination [36,37]. These losses ultimately limit Q: Low temperature experiments on quartz have demonstrated SAW resonators with Q m × f [GHz] > 10 5 [21,22]. Another source of losses is due to mode-conversion into bulk-modes.…”

“…(3) Our scheme is built upon an established technology [14,15]: Lithographic fabrication techniques provide almost arbitrary geometries with high precision as evidenced by a large range of SAW devices such as delay lines, bandpass filters or resonators etc. In particular, the essential building blocks needed to interface qubits with SAW phonons have already been fabricated, according to design principles familiar from electromagnetic devices: (i) SAW resonators, the mechanical equivalents of Fabry-Perot cavities, with low-temperature measurements reaching quality factors of Q ∼ 10 5 even at gigahertz frequencies [21][22][23], and (ii) acoustic waveguides as analogue to optical fibers [14]. (4) For a given frequency in the gigahertz range, due to the slow speed of sound of approximately ∼ 10 3 m/s for typical materials, device dimensions are in micrometer range, which is convenient for fabrication and integration with semiconductor components, and about 10 5 times smaller than corresponding electromagnetic resonators.…”