[14p-514-1~8] 1.6 Ultrasonics

[14p-514-5] Development of ultrasonic sensor using fiber-based optical-frequency-comb cavity

〇Takashi Msuoka^1,2, Takashi Ogura¹, Takeo Minamikawa^1,2, Yoshiaki Nakajima^2,3, Yoshihisa Yamaoka⁴, Kaoru Minoshima^2,3, Takeshi Yasui^1,2 (1.Tokushima Univ., 2.JST, ERATO IOS, 3.UEC, 4.Saga Univ.)

Keywords:Ultrasonic wave, fiber based on sensor, Optical-frequency-comb

Photoacoustic (PA) imaging is a hybrid imaging method of light and ultrasonic wave, and it is expected as a biological imaging method that combines the characteristics of light that enables molecular selectivity and the characteristics of ultrasonic wave that enables observation deep in the living body . In general, the ultrasonic wave signal is detected by an electric ultrasonic transducer. However, the low sensitivity of the electric ultrasonic transducer limits the penetration depth of PA imaging. To realize high sensitive detection of the ultrasonic wave, we developed a new sensor using fiber-based optical-frequency-comb (OFC)
OFC shows a spectral structure in which a large number of optical modes that are arranged at equal intervals in the frequency domain of the ultrashort pulse laser. The spectral spacing of the optical-frequency-comb exactly coincides with the repetition frequency of the ultrashort pulse laser in the time domain, and the signal exists in the RF region. The repetition frequency of this pulse is accurately determined by the optical path length of the laser cavity. Therefore, the OFC cavity can be used as a highly accurate sensor. In this report, we evaluated the measurement performance of ultrasonic wave (6 to 12 MHz) applied to a OFC cavity as a fundamental research for the application to a PA imaging.