Nanometer-resolution distance and surface structure measurement bv incoherent laser-feedback

We provide a simple analysis to explain how the wavelength of a diode laser is shifted by the strong, incoherent optical feedback. Our preliminary experiments indicate that, in addition to wavelength changes, the laser diode´s driving current is also extremely sensitive to the feedback. Thus, by detecting the bias current variations we could obtain similar nm ranging resolution without the complexity of a spectrometer. The technique can be made more compatible with integrated optics and existing technologies facilitating its applications in more difficult physical environments that may exist in industry or a medical´setting. Experimental results are provided that show 3-D surface structure imaging obtained by implementing this incoherent confocal laser-feedback technique in a scanning microscope.