Ranging and interferometry with a frequency shifted feedback laser L.P. Yatsenko a , B.W. Shore b, * , K. Bergmann b a Institute of Physics, Ukrainian Academy of Sciences, Prospect Nauki 46, Kiev-39, 03650, Ukraine b Universita ¨ t Kaiserslautern, 67653 Kaiserslautern, Germany Received 15 May 2004; accepted 30 August 2004 Abstract The potential advantages of chirped pulses for very precise measurement of distance, through frequency-domain ranging, has prompted consideration of frequency shifted feedback (FSF) lasers as sources of interferometer light. We here derive theoretical limitations to the spatial accuracy one can expect in such applications, by considering ana- lytical expressions for the electric field emerging from a frequency shifted feedback (FSF) laser seeded by a CW laser whose finite bandwidth originates in phase fluctuations. We also consider consequences of fluctuations in cavity size. We show that, for surfaces flat within the laser footprint, such a system can provide the subwavelength accuracy of conventional interferometry but without dependence on material-dependent phase shifts. Although noise has been important for previous uses of FSF lasers in optical ranging and interferometry, we here show that a frequency mod- ulated seeding laser can be used to better advantage than noise. Ó 2004 Elsevier B.V. All rights reserved. PACS: 42.55.f; 42.60.Da; 42.55.Ah Keywords: Optics; Lasers; Frequency shifted feedback; Interferometry; Profilometry; Frequency-domain ranging 1. Introduction Rapid and nonintrusive measurements of dis- tances from millimeter to kilometer with accura- cies of microns or less are now feasible using techniques of optical frequency domain ranging (OFDR) wherein a measurement of distance is ob- tained from a measurement of frequency differ- ences [1–5]. The technique can be regarded either as a form of chirped optical radar [6] or as a form of interferometry using chirped laser input. As has been demonstrated, [7,8] the needed interferometer seed laser can use the technique of frequency- 0030-4018/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.optcom.2004.08.051 * Corresponding author. Present address: Department of Physics, 618 Escondido Cir, Livermore, CA 94550, USA. Tel.: +1 925 455 0627. E-mail address: bwshore@alum.mit.edu (B.W. Shore). Optics Communications 242 (2004) 581–598 www.elsevier.com/locate/optcom