Moderate-coherence sensing with optical cavities: ultra-high accuracy meets ultra-high measurement bandwidth and range

• Published in: Communications engineering 2024-01, Vol.3 (1), p.17-8, Article 17
• Main Authors: Dickmann, Johannes, Shelling Neto, Liam, Sauer, Steffen, Kroker, Stefanie
• Format: Article
• Language: English
• Subjects: 639/166/984; 639/166/988; 639/624/1075/1083; 639/624/1107; Accuracy; Bandwidths; Coherent electromagnetic radiation; Electromagnetic radiation; Engineering; Gravitational waves; Holes; Interferometry; Lasers; Radiation; Semiconductor lasers; Sensors; Silicon wafers; Spectrum allocation
• ISSN: 2731-3395; 2731-3395
• DOI: 10.1038/s44172-024-00164-w

Interferometric sensors, renowned for their exceptional accuracy, leverage the wave properties of coherent electromagnetic radiation. The periodicity of the measurement signal often critically limits the measurement range of sensors utilizing interferometry. Here we introduce a cavity-based interferometry concept that capitalizes on a laser with moderate coherence, thereby combining ultra-high accuracy with ultra-high measurement bandwidth and range. To this end mid-fringe detection is combined with measurements of the interferometric visibility. We present experimental results that demonstrate the effectiveness of our approach exemplarily for length sensing. Notably, our system achieves an accuracy of 1 nm with a measurement range of 120 μm (relative uncertainty of 0.00083 %) and a bandwidth ranging from 0 Hz to 20 kHz. These findings support advancements in high-precision sensing applications that demand simultaneous accuracy, measurement range and bandwidth. Dickmann and colleagues present an interferometric sensing scheme that delivers improved accuracy with wider dynamic range and high speed. They use the multiple modes of a Fabry-Perot laser diode with the weighted power to measure with moderate coherence and thus break up the periodicity of the sensor signal.