Highly thermal-stable heterodyne interferometer with minimized periodic nonlinearity

Area of Science:

• Optics and Photonics
• Metrology
• Interferometry

Background:

• Heterodyne interferometers are susceptible to thermal drift of optics (TDO), causing significant measurement errors.
• Periodic nonlinearity (PNL) is another common error source in interferometric measurements.

Purpose of the Study:

• To propose and experimentally validate a symmetric heterodyne interferometer capable of eliminating TDO and PNL.
• To achieve high-precision measurements by mitigating common error sources in interferometry.

Main Methods:

• A symmetric heterodyne interferometer with spatially separated beams was designed for balanced optical paths.
• A specialized vacuum experimental setup was used for TDO testing.
• Frequency domain and phase quadrature methods were employed for PNL measurement.

Main Results:

• The proposed interferometer achieved a thermal coefficient of 1.2 nm/°C, significantly reducing TDO effects.
• Periodic nonlinearity (PNL) was measured to be undetectable at a noise level of 13 pm.
• The design successfully balanced optical paths and avoided optical mixing.

Conclusions:

• The symmetric heterodyne interferometer effectively eliminates TDO and PNL, offering a significant advancement in precision measurement.
• This design provides a robust solution for applications requiring high accuracy and stability in the presence of thermal variations.