Phase sensitivity in single-shot speckle interferometry using a custom integrating glass-sphere for the measurement of femtometric wavelength change

• Published in: Optics and lasers in engineering 2023-02, Vol.161, p.107382, Article 107382
• Main Authors: Saucedo, B., Dávila, A., Rayas, J.A., Peña-Cruz, M.I.
• Format: Article
• Language: English
• Subjects: Digital holography; Speckle; Spectroscopy
• ISSN: 0143-8166; 1873-0302
• DOI: 10.1016/j.optlaseng.2022.107382

•Phase depends on: dimensions of the optical setup, the internal reflection coefficient, the diameter, and glass index of the integrating sphere.•It is shown that for the correct processing of phase in this kind of interferometer, it is necessary to avoid the singularities of optical vortices.•The OPD can be chosen to detect a wavelength change of tens of femtometres and customised by changing the reflectance of the integrating sphere. Phase sensitivity single-shot speckle interferometry for detection of wavelength changes in the femtometric scale depends on the optical path differences (OPDs) produced by the multiple reflections inside an integrating sphere. In this work the OPDs are calculated using a ray-tracing program of a glass sphere coated with white paint, which shows that the resulting OPDs are distributed randomly over the speckle field-of-view but with a characteristic curve that depends strongly on the dimensions of the optical setup, the internal reflection coefficient, and the diameter of the integrating sphere that combined produce the final phase sensitivity of the optical setup. It is also shown that singularities removal of vortices is necessary for the phase-change calculation. The ray-tracing simulations of the proposed optical setup are confirmed by the experimental results of the optical implementation.