Optical Detection of Ultrasound

Stabilized Fiber Optic Sensor for Ultrasound Detection

“…However, for displacements much less than the wavelength of laser light, only local oscillations about a point will occur. Typical displacements associated with ultrasound are small, 1 to 50 nm [19], compared to the wavelength of light we are using, 780 nm. Consequently, we expect local oscillations about a point to result.…”

Sensitivity of an Embedded Fiber Optic Ultrasound Sensor

“…Shot noise lirnited phase shift: The shot noise lirnited minimum detectable phase shift for a path stabilized interferometer has been investigated by Wagner [8]. The following expression for the signal to noise ratio (SNR) of a path stabilized interferometer results by dividing the root-mean squared signal current from the photodetector by the root-mean squared noise current [9] : (7) where 11 is the photodetector efficiency, h is Planck's constant, v is the frequency of light, Bis the bandwidth ofthe measurement, P 518 is the signal intensity, and Pis the averagelight intensity on the detector.…”

“…The following expression for the signal to noise ratio (SNR) of a path stabilized interferometer results by dividing the root-mean squared signal current from the photodetector by the root-mean squared noise current [9] : (7) where 11 is the photodetector efficiency, h is Planck's constant, v is the frequency of light, Bis the bandwidth ofthe measurement, P 518 is the signal intensity, and Pis the averagelight intensity on the detector. The averagelight intensity and signal intensity given in Eq.…”

Technique for Measuring Spatial Distribution of the Surface Acoustic Wave Velocity in Metals

“…The velocity of the surface acoustic waves is determined by measuring the distance between the SAW emitting and receiving areas and also by the respective propagation time of the acoustic wave. To measure the velocity one uses the SAW transmission and reception by utilizing contact piezoelectric transducers (Murav'ev et al, 1996; Zhi et al, 2000; John-son, 1993) or non-contact laser techniques (Wagner, 1990). To determine the spatial distribution of the SAW velocity several measuring schemes are used.…”