Ultrasound detection via low-noise pulse interferometry using a free-space Fabry-Pérot

source: © 2018 Optical Society of America

Coherence-restored pulse interferometry (CRPI) is a recently developed method for optical detection of ultrasound that achieves shot-noise-limited sensitivity and high dynamic range. In principle, the wideband source employed in CRPI may enable the interrogation of multiple detectors by using wavelength multiplexing. However, the noise-reduction scheme in CRPI has not been shown to be compatible with wideband operation. In this work, we introduce a new scheme for CRPI that relies on a free-space Fabry-Pérot filter for noise reduction and a pulse stretcher for reducing nonlinear effects. Using our scheme, we demonstrate that shot-noise-limited detection may be achieved for a spectral band of 80 nm and powers of up to 5 mW. [Read More…]

Fig. 1 A schematic of CRPI. EDFA is erbium-doped fiber amplifier; PZ is piezoelectric fiber stretcher; CRF is coherence-restoring filter; and π-FBG is π-phase-shifted fiber Bragg grating. The pulse train from the laser is filtered to a bandwidth of 0.4 nm, amplified, and further filtered by the CRF. Shifts of resonance of the π-FBG are measured by optical demodulator, implemented by a Mach-Zehnder interferometer locked to quadrature.

Oleg Volodarsky, Yoav Hazan, and Amir Rosenthal, “Ultrasound detection via low-noise pulse interferometry using a free-space Fabry-Pérot,” Opt. Express 26, 22405-22418 (2018)