## 5 Conclusions  
When an oil immersion objective is used in an interferometric measurement system that undergoes laser power changes, an additive phase term caused by the immersion oil reaction will be present. This effect occurs when coupling an interferometer and an optical trap, where the latter is used to manipulate the object under test that the interferometer will measure. To obtain a correct interferometer measurement, that additive phase term must be removed from the measurement. In this study, it is demonstrated that the immersion oil, which is required by the microscope objective, is the component that reacts to the change in laser power, causing a phase shifting in the observed interferograms. Therefore, the immersion oil was analyzed optically, thermally, and morphologically, independent of the trap-interferometer setup. It was concluded that when there is a change in the laser source, it is necessary to calibrate the additive phase term in the trap-interferometer array, to subsequently considered it in the measurements, as presented in Section 4.1.  
The direct applications of this study impact microscopes that use immersion oil and are used to measure a certain parameter. In addition, since power decreases during the useful life of a laser, it would be necessary to implement the calibration described herein on a periodic basis. Another calibration would imply characterizing the ray convergence point of an oil immersion microscope objective, depending on the application and the equipment used. For example, for techniques such as microscopic interferometry, digital holographic microscopy, or 3D flow cytometry, the phase term added due to the change in the oil refractive index would have to be considered. In the same sense, for an optical trap or a confocal microscope, there would be a change in the system's optical geometry. More robust work concerning the optical, thermal, and morphological behavior of the material discussed here is left open.  
It is reiterated that the time-dependent change in volume corresponds to the change in temperature and refractive index, since oil expands with heat. In addition, as the laser power increases, the WD decreases, the trap gradient force is higher, the oil is excited, and the oil's \(n\) decreases; thus, there is a piston in the phase maps.  
Conceptualization, J.A.R.; methodology, A.D.D.-F. and J.A.R.; software, A.D.D.-F. and J.A.R.; validation, J.A.R.; formal analysis, A.D.D.-F. and J.A.R.; investigation, A.D.D.-F. and J.A.R.; resources, J.A.R., A.M.-G. and R.R.C.; data curation, J.A.R.; writing--original draft preparation, A.D.D.-F. and J.A.R.; writing--review and editing, J.A.R., A.M.-G. and R.R.C.; visualization, A.D.D.-F. and J.A.R.; supervision, J.A.R.; project administration, J.A.R. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Consejo Nacional de Humanidades, Ciencias y Tecnologias, grant number 758043.  
Not applicable.  
Data Availability StatementThe data here presented is accessible for research purposes upon direct request from the authors. Requests for access should be directed to the corresponding authors in line with established academic protocols.  
The authors declare no conflicts of interest.