TEMPO is based on photorefractive two-wave mixing. A dynamic hologram (resulting from the interferences between the reference beam and the signal beam) is recorded in the photorefractive crystal. The response time of the process permits to compensate the slow phase change (low frequency acoustic vibration for example) of the signal beam but not the fast change at high frequencies (>1 kHz). The diffraction of the reference beam by the dynamic hologram creates a local oscillator adapted to the signal i.e. same wavefront and same direction. Two-wave mixing in a photorefractive material is equivalent to an adaptive beam splitter. The two beams - signal and adapted local oscillator - are in perfect quadrature and are incident on the photodetector that delivers a homodyne signal.

We use high performances photorefractive crystal with reliable properties to insure an optimum two-wave mixing process. A high voltage field is applied on the photorefractive crystal in order to optimize the coupling and maintain the quadrature between the signal and the diffracted reference (adapted local oscillator). Photorefractive two-wave mixing has been extensively studied over the past 40 years and is a well-controled process. For more information on technical litterature, please consult TEMPO ressources and/or contact us.

Taking advantage of the large collection aperture of TEMPO makes it possible to implement the simultaneous measurement of in-plane and out-of-plane surface displacement. We propose TEMPO 2D, dedicated to in-plane and out-of-plane displacement measurement. TEMPO 2D has the same footprint and optical architecture as TEMPO 1D (out-of-plane measurement) and delivers 2 output signal (in-plane and out-of-plane).

For more technical detail about TEMPO 2D, please consult the technical notes in TEMPO ressources.

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