ZnO Thin Films and Their Application to Germanium Acousto-optic Modulators
The deposition system and parameters for repeatably producing highly oriented ZnO thin films suitable for high frequency acousto-electric transducers are described. At the high super-saturations used the state of the nucleating surface and the partial pressure of oxygen, in the sputtering gas mix, are shown to critically affect the texture and stress level in the film. The performance of a germanium acousto-optic modulator employing a ZnO thin film transducer is compared with that expected theoretically. The photoelastic constant of germanium at 10.6 μ is shown to be 0.42 ± 0.05. The analysis indicates that a germanium acoust-ooptic modulator could be used to efficiently couple energy out of a CO2 laser.