Spectrum analysis of acousto-optic signal modulated by ultrasound at different frequency in scattering medium

Ultrasound-modulated optical tomography (UOT) combines optical and acoustic techniques, and has high spatial resolution of ultrasonic location and high sensitivity of optical detection. In this technique, a focused ultrasound is used to locate and label the scattered light. It determines the spatial resolution of UOT and the modulation efficiency of the scattering light. Four kinds of acousto-optic signals modulated by 1, 2.25, 5, and 10 MHz center frequencies of impulse ultrasound are obtained in this letter. The frequency spectrum of these four kinds of acousto-optic signals are achieved by Fast Fourier Transform (FFT). By analyzing the spectrum information of acousto-optic signals modulated by ultrasound at different frequencies, we can find useful feature information and choose an appropriate parameter of ultrasonic probe to improve the signal-to-noise ratio and sensitivity of UOT.