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Photorefractive Interferometer For Industrial Laser-UT Applications
  The TWM is a fully integrated laser-ultrasonic detection unit for non-contact measurement of ultrasond. Laser-ultrasonics is a non-destructive inspection technique, which combines the precision of conventional ultrasonic inspection with the ease of use of optical techniques. The TWM is available in two model: a high sensitivity model, for laboratory investigation, and a fast-response model, for operation in industrial or noisy environment.
  In the TWM, a pump beam and a signal beam, which carries the ultrasonic information in the form of a phase modulation, interfere inside a photorefractive crystal. Through the photorefractive effect, an index grating is created inside the crystal that reproduces the illumination (signal beam) interference pattern. The index grating then diffracts the pump beam. Thus, as shown in the figure, a reference beam is created with the same spatial structure as the signal beam. Such a process can be viewed as “real-time” holography. The signal beam transmitted through the crystal interferes on the optical detector with the diffracted pump beam (reference signal) to perform phase demodulation and to give an electrical signal proportional to the surface displacement.
  The TWM is available with an integrated frequency-stabilized continuous wave Nd:YAG laser operating at a wavelength of 1064 nm.  The laser power outputs are available for the detection laser ranging from 500 mW up to 2 W. With the detection laser head integrated inside the TWM unit, all of the laser output power is used to “pump” the photorefractive crystal. With this configuration, the optimum response time for the two-wave mixing setup is achieved, for a given laser source. For industrial application where even more laser power is required, the TWM can easily be coupled TECNAR’s pulsed detection laser, the PDL.
  The TWM is supplied with an optical probe that focuses the detection laser light on the target’s surface and collects the back-scattered light. The probe is link to the TWM unit with optical fibers housed in protective flexible tubing. The optical probe can be customized to your specifications.
  The TWM can also be supplied for operation with an external the detection laser. A fiber input is provided to easily inject the pump beam inside the TWM unit. An optional module to split the external laser into pump and illumination beams is also available at TECNAR.
  To know more about this system or to receive a quotation, please do not hesitate to contact us at:

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