Abstract
Even after the Heydemann correction, residual nonlinear errors, ranging from hundreds of picometers to several nanometers, are still found in heterodyne laser interferometers. This is a crucial factor impeding the realization of picometer level metrology, but its source and mechanism have barely been investigated. To study this problem, a novel nonlinear model based on optical mixing and coupling with ghost reflection is proposed and then verified by experiments. After intense investigation of this new model’s influence, results indicate that new additional high-order and negative-order nonlinear harmonics, arising from ghost reflection and its coupling with optical mixing, have only a negligible contribution to the overall nonlinear error. In real applications, any effect on the Lissajous trajectory might be invisible due to the small ghost reflectance. However, even a tiny ghost reflection can significantly worsen the effectiveness of the Heydemann correction, or even make this correction completely ineffective, i.e., compensation makes the error larger rather than smaller. Moreover, the residual nonlinear error after correction is dominated only by ghost reflectance.
Highlights
Picometer level metrology faces increasing demand in numerous key fields, such as gravitationalwave detection, semiconductor industry, and nanotechnology [1,2,3,4,5]
Metrology, a novel nonlinearity model based on ghost reflection and its coupling with optical mixing
The influence of the developed model on the metrology, a novel nonlinearity model based on ghost reflection and its coupling with optical mixing
Summary
Picometer level metrology faces increasing demand in numerous key fields, such as gravitationalwave detection, semiconductor industry, and nanotechnology [1,2,3,4,5]. Doppler frequency shiftoptical (DFS) paths arisingand from ghost compensation algorithms, mainly the Heydemann correction [12,13,14,15,16,17] This correction relies on the reflection [11]. To study the residual nonlinear errors impeding the realization of picometer level compensation [12,13,14,15,16,17], the cause and mechanism of which remain largely uninvestigated. Metrology, a novel nonlinearity model based on ghost reflection and its coupling with optical mixing. The influence of the developed model on the metrology, a novel nonlinearity model based on ghost reflection and its coupling with optical mixing. Nonlinearity Model Based on Ghost Reflection and Its Coupling with Optical Mixing
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