One-frequency laser interferometer using the optic fiber as a polarization-independent interference phase detector

A soft X-ray scanning microscope is built on the X-ray ring's undulator beam line. The beam line will provide more powerful coherent soft X-ray flux to improve the resolution of scanning microscopy to the sub-1000A range and form pictures in seconds rather than minutes. A laser interferometer was developed for encoding the coordinates of the scanning plane of the soft X-ray microscope with 300A resolution. A pair of the optical fibers was used as an interference fringe phase detector in the interferometer which can make the system phase adjustment simpler, more accurate, and polarization-independent. The last character is important because if the fringe phase detector is polarization dependent the interferometer's optical design will be complicated when the optical path of the interferometer has to include additional windows or mirrors which usually change the polarization situation. The optical arrangement of the interferometer is discussed and the schematics of the resolution extending unit and the interferometer's other possible applications are described.