Michelson cum Mach-Zehnder interferometer

Another optical schematic comprising a Michelson and a Mach-Zehnder interferometer into a single set up is proposed for simultaneous studies described above. The combined interferometer is shown in Figure 4.71. The incoming laser beam is split into two beams using a beam splitter. In order to get the surface structure details, the two beams split by the first beam splitter (BS1) are used along with an optical glass window (W) to form a Michelson interferometer. Under normal incidence, approximately light intensity is reflected from the front surface of the glass window. This reflected beam from the window becomes the reference beam of the Michelson interferometer and interferes with a second beam that is obtained after reflection from the crystal surface. This results in a Michelson interferogram that carries the microstructure details of the growing crystal surface. In order to obtain solution characteristics, the two beams split by the first beam splitter (BS1) are used again. These are folded using mirrors (M1 and M2) and beam-splitters (BS1 and BS2) placed at the corners of a rectangle to form a Mach-Zehnder interferometer. The intensity of the reference beam that gets transmitted through the glass window used for the Michelson interferometer interferes with the beam that passes through the chamber where the crystal is growing. The interference of these two beams yields a Mach-Zehnder interferogram that carries details of the thermal, concentration and convective field around the growing crystal. In this manner two interferograms are obtained simultaneously on two CCD cameras to result in the microtopography as well as transport characteristics during growth.