How interferometry in optical measurements improves precision and accuracy

Principles of interferometry

Interferometry is a powerful technique in optical measurements that utilizes the interference of light waves to achieve high precision and accuracy. It works by splitting a coherent light source into two or more beams, which travel different paths before recombining. The resulting interference pattern provides information about the optical path difference between the beams.

Improvements in precision

Enhanced sensitivity

Interferometry significantly improves measurement precision by enhancing sensitivity to small changes in optical path length. The interference pattern can detect variations on the order of a fraction of the wavelength of light, allowing for extremely precise measurements (Kaiser et al., 2017). This high sensitivity enables the detection of minute changes in distance, refractive index, or other optical properties.

Quantum enhancement

Recent advancements in quantum optics have further improved the precision of interferometric measurements. Quantum-enhanced interferometry, utilizing entangled photon pairs, has demonstrated a 2.4 times better measurement precision compared to classical methods, while requiring 62 times fewer photons (Kaiser et al., 2017). This quantum advantage arises from exploiting both spectral and photon-number correlations of energy-time entangled photon pairs.

Improvements in accuracy

Reduction of systematic errors

Interferometry can improve measurement accuracy by reducing systematic errors. In quantum white-light interferometry, for example, the number of fitting parameters is significantly reduced, which eliminates systematic errors and leads to an absolute determination of material parameters (Kaiser et al., 2017). This reduction in systematic errors is particularly beneficial for characterizing optical materials and components.

Absolute distance measurements

Interferometry enables high-accuracy absolute distance measurements. For instance, dispersive interferometry using femtosecond optical frequency combs has achieved absolute distance measurements with errors less than 12 μm over a range of 70 m (Niu et al., 2022). This level of accuracy is crucial for applications in industrial metrology and scientific research.

Applications and benefits

Material characterization

Interferometry is particularly useful for characterizing optical materials. It allows for precise measurements of properties such as chromatic dispersion in optical fibers (Kaiser et al., 2017). The improved accuracy and precision in these measurements contribute to the development of better optical components and systems.

Astronomical observations

In astronomy, intensity interferometry has gained increasing interest for high-resolution imaging. This technique is insensitive to atmospheric turbulence and doesn't require high-precision optical path control, making it suitable for large-scale telescope arrays (Zmija et al., 2023). It has been successfully implemented in existing telescope systems for measuring angular diameters of stars and studying multiple star systems.

Spin-orbit torque measurements

Sagnac interferometry has shown significant improvements in signal-to-noise ratio for magnetic imaging compared to conventional magneto-optical Kerr effect methods. This enhancement allows for quantitative measurements of current-induced magnetic deflections due to spin-orbit torque, even in thin-film magnetic samples with perpendicular magnetic anisotropy (Karimeddiny et al., 2021).

Conclusion

Interferometry significantly enhances both precision and accuracy in optical measurements through its inherent sensitivity to small changes in optical path length, reduction of systematic errors, and ability to perform absolute measurements. These improvements, coupled with recent advancements in quantum optics, have expanded the capabilities of optical metrology across various fields, from material science to astronomy. The continued development of interferometric techniques promises to push the boundaries of measurement precision and accuracy even further, enabling new discoveries and applications in science and technology.