An intuitive picture of the physics underlying optical ranging using frequency shifted feedback lasers seeded by a phase-modulated field

• Published in: Optics communications Vol. 282; no. 11; pp. 2212 - 2216
• Main Authors: Yatsenko, L.P., Shore, B.W., Bergmann, K.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-06-2009; Elsevier
• Subjects: Biological and medical applications; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Interferometers; Metrological applications; Optical instruments, equipment and techniques; Optics; Physics; 42.62.Eh; 42.55.−f; 42.60.Da; 42.30.−d; 42.30.-d; 42.55.-f; Light interferometry; Phase modulation; Michelson interferometers; Measuring methods; Signal-to-noise ratio; Laser beam applications; Frequency shift; Feedback; Optical method; Distance measurement
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2009.02.042

Frequency shifted feedback (FSF) lasers have been demonstrated to have interesting and useful features when used for optical ranging. The use of a phase-modulated seed to the FSF laser dramatically improves the signal-to-noise ratio, enabling distance measurements with the accuracy expected of optical interferometry. We present here an intuitively accessible description of the physics that underlies this dramatic enhancement of optical ranging signals. Unlike a free-running FSF laser, each one of the many equidistant frequency components of the seeded FSF laser spectrum (typically >104) has a definite amplitude, and a phase which varies with component number and modulation frequency Ω of the seed radiation. Suitable adjustment of Ω gives all components a common phase; the resulting constructive interference enhances the signal by orders of magnitude.