We have developed a fiber-optic interferometer optimized for best performance in the frequency range from DC to 1 kHz, with displacement linearity of 1 % over a range of ± 25 nm, and noise-limited resolution of 2 pm. The interferometer uses a tunable IR laser source (nominal 1550 nm wavelength) with high amplitude and wavelength stability, low spontaneous self-emission noise, high sideband suppression and a coherence control feature. The amplitude stability of the source, combined with the use of specially manufactured bend-insensitive fiber and all-spliced fiber construction, result in a robust homodyne interferometer system which achieves resolution of 40 fmHz-1/2 above 20 Hz and approaches the shot-noise-limit of 22 fmHz-1/2 at 1 kHz, without the need for differential detection, and at working distances as large as a millimeter from a suitably reflecting surface. Here we describe the design and construction of the interferometer, and demonstrate its use in the measurement of picometer-scale motions in atomic-scale mechanics studies.
Citation: Review of Scientific Instruments
Pub Type: Journals
interferometry, fiber optics, length metrology