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The Wedged Optical Flat is Held in Place with Three Magnets.
These Shearing Interferometers can be used with incident beams as small as Ø1 mm and as large as Ø50 mm depending on which shear plate is used. The interference pattern is sensitive to the beam divergence and can be used to qualitatively determine whether the beam is collimated. As shown in the figure to the right, the plate has three steel balls fixated to the bottom of the plate, which attach magnetically to the base. This magnetic retention mechanism enables easy swapping of plates when different beam diameters are used. Please see the Specs tab for compatible plates and bases.
In addition, there is a hole drilled into the back of the base plate, thus enabling the light that is transmitted through the wedged optical flat to continue unimpeded. For all models except the SI500, this hole is SM1-threaded (1.035"-40). The base plate, diffuser plate, and shear-plate come packaged in an aluminum carrying case.
Plates Compatible with Multiple Shearing Interferometer Bodies
Magnetic Steel Balls Secure the Plate to the Base
Applicable Beam Diameters Engraved on Plate
Thorlabs offers five interchangable shear plates, which together are designed to be used with incident beam diameters ranging from 1 mm to 50 mm. The magnetically coupled kinematic design of these plates allows them to be precisely located on the shearing interferometer. Multiple plates are compatible with the same base (see the table below for compatibility), thus enabling the plate to be interchanged easily if the beam diameter being used for particular experiment changes. Different shear plates are offered for different diameter beams due to the optimization of the wedge angle for the beam diameter.
The SIVS accessory is helpful for viewing the fringe pattern created by a small diameter beam. By replacing the standard diffuser plate viewing screen on the SI035, SI050, SI100, or SI254* with this accessory, the size of the fringes will increase, thereby making it easier to determine if the light is collimated. The SIVS comes packaged with two 1/16" screws so that it can be secured to the shearing interferometer.
If desired, the mounting plate for the SIVS can be purchased separately (SITST). It features a standard Thorlabs SM1 (1.035"-40) thread, which is compatible with any of our SM1-threaded components.