Calibration of the Fabry-Pérot free spectral range using a tunable laser in a Michelson interferometer

Abstract

Abstract. Coherent interferometric absolute distance metrology enables different techniques for length metrology. Measurements are made without ambiguity, by using either one or several synthetic wavelengths resulting from the beating of two or more wavelengths or, in the case of frequency sweeping interferometry ͑FSI͒, from a frequency sweep. These techniques require accurate measurements of the frequency variation, a task which is usually performed with a Fabry-Pérot ͑FP͒ interferometer. Sensor performances are highly dependent on the FP free spectral range ͑FSR͒, which must be accurately known. We describe a method to measure the FSR of an FP using a tunable laser in a Michelson interferometer, using both absolute and relative distance measurements. The optical setup is based on a frequency-sweeping sensor and a controlled translation table. An uncertainty of 45 ppm in the measurement of a 1-GHz FSR is obtained. The method is indicated for the calibration of the FP in the frequency-sweep-range-measuring subsystem of a frequency sweeping sensor absolute distance sensor as it does not require any addition hardware, configuring a self-calibration approach.

Dimensional Metrology and Frequency Sweeping Interferometry

“…The FP has a free spectral range of 1 GHz (TOPTICA high resolution, temperature stabilized, confocal Fabry-Pérot with a real finesse up to 1000). The FP was calibrated using the sensor hardware by means of two absolute measurements and a relative calibrated distance measurement between the two absolute positions, a kind of self-calibration (Cabral & Rebordão, 2006). This is a simple procedure and thus highly convenient to be implemented in space applications.…”

Advances in wide-tuning and narrow-linewidth external-cavity diode lasers

“…The mode-hop-free tuning of lasers is important in many applications. For example, it can prevent the distortion of interference fringes in frequency-scanning interference [74] and reduce measurement uncertainty [75]. However, the tuning range is still limited without mode hopping in practice owing to mechanical errors, vibrations, gain chip surface reflectivity, temperature, and air conditions.…”

Extending the mode-hop-free tuning range of an external-cavity diode laser by synchronous tuning with mode matching

“…The interference fringes will be distorted when mode hops occur [5]. Also, a wider mode-hop-free (MHF) tuning range will lead to a lower uncertainty of measurement [6]. Consequently, the MHF tuning ranges of ECDLs are critical for an FSI system.…”