Fig. 1: Working principle and characterization of the laser-based ultrasound sensor. | Nature Communications

Fig. 1: Working principle and characterization of the laser-based ultrasound sensor.

From: Optical-resolution functional gastrointestinal photoacoustic endoscopy based on optical heterodyne detection of ultrasound

Fig. 1

a Schematic of the laser sensor. Ultrasound waves modulate the sensor geometry with a coefficient Sm. b Vector diagram for measurement of the signal vs with an acoustically induced phase modulation Δθ. The noise (gray shading) is decomposed into the in-phase component Ni and quadrature-phase component Nq. c Heterodyne phase detection. The acoustic response in laser phase variation is amplified by the gain factor G. The induced phase variation is then read out at radio frequencies via heterodyne detection. d–f Measured phase response, phase noise, and NEPD spectra. RF: radio frequency. NEPD: noise-equivalent pressure density.

Back to article page