Axial response in semiconductor laser confocal interferometric microscope under full optical feedback
We compare the performance of the optical feedback semiconductor laser Michelson interferometer (OSMI), optical feedback Mach-Zehnder feedback interferometer (OMZI), and full feedback OSMI in terms of the interferogram contrast and the axial response produced when the sample mirror is scanned under a confocal configuration. The OMZI interferogram shows peaks of varying contrast when the length of one of its arms is changed from –λ to λ. An iterative method is formulated to approximate the steady state interferogram that is generated by a full-feedback OSMI which involves an infinite number of optical reflections of the laser output power. The OSMI, OMZI, and full feedback OSMI interferograms have periods of λ/2 with the full feedback OSMI interferogram producing the highest contrast among the three. The full feedback OSMI also produces the narrowest axial response as computed from the fullwidth at half maximum (FWHM) of the perturbed laser output power.