The Surface Acoustic Wave (SAW) technique is applied for the first time to quantify the properties of a responsive polymer brush layer. Using a single SAW chip, the response of five different brush compositions to several pH changes was monitored in parallel in a single run. These results were compared with QCM-D studies on the same system. SAW exhibited two remarkable advantages against QCM-D: (i) multiplexing capability, which allowed considerable reduction in experimental time and expenses (1/8 reduction of experimental time, 1/5 in the number of chips, and 1/10 in solvent consumption in our case), and (ii) higher sensitivity in both mass and viscosity change than QCM-D (4-5 times higher in our systems). Our results demonstrate the suitability and advantages of the SAW technology for application in polymer science, in particular for the study of the compositional effects in responsive thin layers.

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The design and implementation of in-fiber acousto-optic (AO) devices based on acoustic flexural waves are presented. The AO interaction is demonstrated to be an efficient mechanism for the development of AO tunable filters and modulators. The implementation of tapered optical fibers is proposed to shape the spectral response of in-fiber AO devices. Experimental results demonstrate that the geometry of the tapered fiber can be regarded as an extra degree of freedom for the design of AO tunable attenuation filters (AOTAFs). In addition, with the objective of expanding the application of AOTAFs to operate as an amplitude modulator, acoustic reflection was intentionally induced. Hence, a standing acoustic wave is generated which produces an amplitude modulation at twice the acoustic frequency. As a particular case, an in-fiber AO modulator composed of a double-ended tapered fiber was reported. The fiber taper was prepared using a standard fusion and pulling technique, and it was tapered down to a fiber diameter of 70 μm. The device exhibits an amplitude modulation at 2.313 MHz, which is two times the acoustic frequency used (1.1565 MHz); a maximum modulation depth of 60%, 1.3 dB of insertion loss, and 40 nm of modulation bandwidth were obtained. These results are within the best results reported in the framework of in-fiber AO modulators.

We show preliminary results of the implantation of a stabilized Michelson interferometer for the characterization of ultrasonic transducers. The detection system consists of a Michelson interferometer in which a feedback system has been integrated to set the interferometer at the linear region of detection and to compensate optical phase changes introduced by environmental vibrations; this allows us to work in the most sensible region of the system and obtain output signals proportional to the detected displacements (< 10 nm). The obtained results show that it is possible to detect ultrasonic displacements close to 0,2 nm in a bandwidth of 3 MHz using a He-Ne laser with an output power of 1 mW. Preliminary characterization of ultrasonic displacements generated by an ultrasonic transducer immersed in a water tank was performed using this interferometer.