Aberrations measurement of fiber-end microlens by free-space microoptical ronchi interferometer

We developed a microoptical Ronchi interferometer system in which a V-groove, an out-of-plane grating, a beam splitter, and a 45deg upward reflector integrated on a single silicon chip were used to measure the wavefront aberration caused by a microlens on the fiber front end. By the use of the microelectromechanical systems configuration, the fringe patterns caused by the different spherical aberration and defocus balances of the 0.34-numerical-aperture microlens can be captured and analyzed accordingly. As demonstrated by the experimental results, the proposed setup is capable of carrying out a simple wavefront variation measurement in the microscopic scale