Air-wedge shearing interferometer

There are four nearly equal intensity Fresnel reflections (~4% for refraction coefficient 1.5) from the air-wedge interferometer (Fig.1): The angle between beams 1-2 and 3-4 is non adjustable and depends only on the shape of the glass wedge.

Because of its extremely thin air-gap, the air-wedge interferometer was successfully applied in experiments with femto-second high-power lasers.

The air-wedge interferogram from even this very short coherence length laser beam exhibits clear, high-contrast interference lines.

[9] But this "classical" air-wedge arrangement has never been used for interferometry with field visualization owing to the overlap of all four reflected beams in the image plane.

Design described in this article eliminates this obstruction and makes the air-wedge interferometer effective for practical applications with a visualization field interferometry.

Figure 1. Beam path inside of air-wedge interferometer.
Figure 3. Example of air-wedge interferometer.
Figure 4. Interferogram of laser-He jet interaction at +15ps.