High-frequency devices operating at 3 GHz or higher are required, for instance, for future 4th generation mobile phone systems in Japan. Using a substrate with a high acoustic velocity is one method to realize a high-frequency acoustic or elastic device. A Lamb wave has a high velocity when the substrate thickness is thin. To realize a high-frequency device operating at 3 GHz or higher using a Lamb wave, a very thin (less than 0.5 μm thick) single-crystal plate must be used. It is difficult to fabricate such a very thin single crystal plate. The authors have attempted to use a c-axis orientated epitaxial LiNbO(3) thin film deposited by a chemical vapor deposition system (CVD) instead of using a thin LiNbO(3) single crystal plate. Lamb wave resonators composed of a interdigital transducer (IDT)/the LiNbO(3) film/air gap/base substrate structure like micro-electromechanical system (MEMS) transducers were fabricated. These resonators have shown a high frequency of 4.5 and 6.3 GHz, which correspond to very high acoustic velocities of 14,000 and 12,500 m/s, respectively, have excellent characteristics such as a ratio of resonant and antiresonant impedance of 52 and 38 dB and a wide band of 7.2% and 3.7%, respectively, and do not have spurious responses caused by the 0th modes of shear horizontal (SH(0)) and symmetric (S(0)) modes.

It has been considered that it is difficult to realize a high-frequency device of 3 GHz or more, for instance, for a fourth generation mobile phone system in Japan, using a conventional surface acoustic wave (SAW) substrate. In this study, we attempted to fabricate a highfrequency resonator using Lamb waves, which has a high velocity and consists of a thin LiNbO 3 film deposited by chemical vapor deposition (CVD). As a result, a 1-port Lamb wave resonator composed of an electrode/thin epitaxial LiNbO 3 film/air-gap/base substrate was fabricated. The measured resonator has a high resonant frequency of 4.5 GHz, which corresponds to a very high velocity of 14,000 m/s, a large impedance ratio of 52 dB, and a relatively wide bandwidth of 7.2%.

This paper describes a micro electromechanical systems type wavelength-selective pyroelectric sensor, with highly c-axis oriented Aluminum nitride film as the pyroelectric material. Wavelength-selective infrared absorption is realized via periodic structures of holes patterned into the top metal electrode that also collects pyroelectric charge signal. The periodic hole array results in optical absorption resonances whose wavelength is determined by the hole pitch, demonstrated experimentally using a Fourier transform infrared spectrometer and numerically calculated using the finite difference time domain method. A significant difference in infrared absorption between patterned and unpatterned detectors is demonstrated through optical experiments comparing the pyroelectric responses.

Currently, a high frequency device more than 3 GHz is required. High frequency resonators with resonant frequencies of 4.5 and 6.3 GHz were fabricated by utilizing an anti‐symmetric first mode (A1) of a Lamb wave having a high velocity consisting of a thin LiNbO3 film deposited by a chemical vapor deposition (CVD) system. By measuring polarities of their LiNbO3 films, it was clarified that the thinner film had a large mixture of +c and −c domains, and the occupation ratio of main polarity influenced their frequency characteristics.