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Refracto-vibrometry is a technique that uses a laser Doppler vibrometer to measure acoustic pressure fields. The vibrometer laser is directed through a medium towards a stationary retroreflective surface. Acoustic waves (density variations) for which the wavefronts pass through the laser, as the beam travels from the vibrometer to the retroreflector and back, cause variations in the integrated optical path length. This results in a time-varying modulation of the laser signal returning to the vibrometer, enabling optical detection of the acoustic wavefronts. In the current experiment, a Polytec PSV-400 scanning laser Doppler vibrometer, sampled at 100 MHz, monitored the waves emitted by a 1 MHz Panametrics V303 ultrasound transducer immersed in a water tank. The time-varying signal detected by the vibrometer at numerous scan points was used to generate videos of the time evolution of acoustic wavefronts; these videos will be presented. Refracto-vibrometry was also used for optical measurements of the time of flight of ultrasonic waves through different materials, including samples of lead and fabricated bone. This enabled determination of wave propagation speeds. The wave speeds obtained with optical detection using refracto-vibrometry were in agreement with measurements using a conventional ultrasonic transducer to detect the wavefronts.
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X-Band Aom on Chip
ilicon Nitride integrated photonic circuits have drawn much attention owing to its ultra-low loss and large Kerr nonlinearity. However, the lack of Pockels effect makes it difficult to be modulated electro-optically, which posts a major challenge for the further development of Si3N4 circuits with advanced functions. The widely adopted thermo-optical tuning suffers from large power consumption and restricted speed (~1 kHz). In this study, microwave frequency modulation (up to 9 GHz) of Si3N4 ring resonator is achieved by exciting bulk acoustic waves piezoelectrically, which modulates the microring via stress-optical effect. The acoustic waves are confined tightly in a released SiO2 thin film which enhances the acoustic energy density and thus modulation efficiency.
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- Award ID(s):
- 1839164
- PAR ID:
- 10292064
- Date Published:
- Journal Name:
- 34th IEEE International Conference on Micro Electro Mechanical Systems (IEEE MEMS 2021)
- Page Range / eLocation ID:
- 210 - 213
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/MEMS51782.2021.9375395
