In this proposal, we will develop high-resolution photoacoustic techniques for generating and detecting acoustic vibrations in nanoscale systems and demonstrate the feasibility of this system in the characterization of doubly clamped NEMS beam resonators.
The current NER proposal seeks to overcome these resolution problems in photoacoustic microscopy and demonstrate its applicability to nanometer scale devices: NEMS. To accomplish this, we will develop an optical near-field photoacoustic microscopy system that will allow us to generate and detect acoustic and thermal vibrations in NEMS devices. This system will have a modulated CW laser (up to 5 GHz) for excitation and a CW probe laser will be used to monitor the local displacement and temperature, respectively. High spatial resolution will be obtained by incorporating a high refractive index solid immersion lens (SIL) to overcome the diffraction limit in air. The SIL based technique is well suited for the generation and detection of acoustic waves in NEMS devices because it allows for reduction of laser spot size below the diffraction limit in air while maintaining the optical throughput necessary for high sensitivity interferometric detection. The proposed research effort is aimed at evaluating this experimental technique, which will act as an enabling technology and help answer fundamental questions regarding the energy flow through these devices. This NER effort will allow for an initial feasibility study on high-resolution photoacoustic microscopy of NEMS and provide the foundation for future development of near-field optical probes for the generation and detection of acoustic phonons in nanoscale structures. Graduate student support is also included in this effort. The students will have a truly interdisciplinary educational experience and receive training in the areas of near-field optics, acoustics, and nanoscale mechanics. This NER specifically addresses the following themes:
