title: Quasi-balanced two-wave mixing interferometer for remote ultrasound detection.
abstract: We present an improved detection scheme for a two-wave mixing interferometer with a Bi12SiO20crystal. The proposed detection scheme allows quasi-balanced detection of ultrasonic signals whereby electrical disturbances are suppressed. Quasi-balancing is achieved by changing the polarity of the high voltage at the photorefractive crystal, leading to an inversion of the optical interference signal, in combination with inversion of the detector signal using a signal inverter before the data acquisition device. The polarity of the high voltage is changed by utilizing an H-bridge consisting of five high-voltage relays. Microcontrollers are used to synchronize the reversion of the high voltage at the photorefractive crystal and the inversion of the measured signals. We demonstrate remote measurement of ultrasonic waves and shown that electrical disturbances are suppressed using the quasi-balanced mode.
authors.affiliation: Research Center for Non-Destructive Testing GmbH (RECENDT), Altenberger Straße 69, 4040 Linz, Austria ; Christian Doppler Laboratory for Photoacoustic Imaging and Laser Ultrasonics, Altenberger Straße 69, 4040 Linz, Austria.
authors.forename: Armin
authors.initials: A
authors.lastname: Hochreiner
authors.affiliation: Research Center for Non-Destructive Testing GmbH (RECENDT), Altenberger Straße 69, 4040 Linz, Austria.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Reitinger
authors.affiliation: Research Center for Non-Destructive Testing GmbH (RECENDT), Altenberger Straße 69, 4040 Linz, Austria.
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Bouchal
authors.affiliation: Christian Doppler Laboratory for Photoacoustic Imaging and Laser Ultrasonics, Altenberger Straße 69, 4040 Linz, Austria.
authors.forename: Saeid
authors.initials: S
authors.lastname: Zamiri
authors.affiliation: Research Center for Non-Destructive Testing GmbH (RECENDT), Altenberger Straße 69, 4040 Linz, Austria ; Christian Doppler Laboratory for Photoacoustic Imaging and Laser Ultrasonics, Altenberger Straße 69, 4040 Linz, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Burgholzer
authors.affiliation: Research Center for Non-Destructive Testing GmbH (RECENDT), Altenberger Straße 69, 4040 Linz, Austria ; Christian Doppler Laboratory for Photoacoustic Imaging and Laser Ultrasonics, Altenberger Straße 69, 4040 Linz, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Berer
keywords: interferometer; laser ultrasound; photoacoustic imaging; quasi-balanced detection; two-wave mixing