Coherent Length Measuring Machine / DTM-CLMI

As a polarizing Michelson interferometer using PBS and 1/4 wave plate, we have measured the coherent length of the background light of the semiconductor laser. First, it takes the alignment of the interferometer in the He-Ne laser and retracts mirrors on the stage, and then collimating light of the semiconductor laser is incident to the interferometer. After removing the laser light by the polarizing plate, the semiconductor laser is observed only the background light by the camera. By adjusting the movable mirror little by little, it can be found the position that the interference fringes appear. The length of the range that is visible the interference fringes will be coherent length.