Vacuum compatible vertical-laser alignment method based on an oil mirror and air-spaced doublets

Area of Science:

• Precision Measurement and Metrology
• Optical Engineering
• Vacuum Technology

Background:

• Vertical lasers are crucial for precision measurements, including kilogram realization using Kibble and joule balances.
• Accurate vertical alignment is essential for metrology and applications like aerospace gravity measurements.
• Existing alignment methods may face limitations in vacuum compatibility or precision.

Purpose of the Study:

• To propose and validate a novel vacuum-compatible vertical laser alignment method.
• To measure and compensate for vertical deviation angles of laser beams with high accuracy.
• To develop a miniaturized, nonmagnetic alignment system for demanding environments.

Main Methods:

• Utilizing dimethyl silicone oil as a natural direction reference in a vacuum.
• Employing air-spaced doublets as focusing elements to translate angular deviation into measurable spot distances.
• Implementing an "air-spaced doublets+aperture" optical element to mitigate off-axis errors.

Main Results:

• Experimental validation of the proposed vacuum-compatible alignment system.
• Demonstration of the system's ability to measure and compensate for vertical laser deviation.
• Achieved a Type B uncertainty of 19.19 µrad for the alignment system.

Conclusions:

• The developed alignment method is vacuum compatible, nonmagnetic, and miniaturizable.
• The system offers significant improvements for mass traceability and potential aerospace applications.
• The novel optical design effectively suppresses critical systematic errors like off-axis error.