Subnanometer absolute displacement measurement using a frequency comb referenced dual resonance tracking Fabry-Perot...

Area of Science:

• Metrology
• Optical Interferometry
• Laser Physics

Background:

• Fabry-Perot (F-P) interferometry is a high-resolution, nonlinear-free displacement metrology technique.
• Single resonance tracking F-P interferometry has limited measurement range.
• Absolute displacement measurement requires high resolution and extended range.

Purpose of the Study:

• To develop a dual resonance tracking (DRT) F-P interferometer system for absolute displacement measurement.
• To achieve a measurement range of tens of millimeters while maintaining high resolution.
• To validate the system's performance against established metrology standards.

Main Methods:

• Utilizing a high-finesse F-P cavity with two external cavity diode lasers (ECDLs) locked to dual resonances.
• Employing the Pound-Drever-Hall locking scheme for laser stabilization.
• Measuring absolute optical frequencies with a reference diode laser stabilized by an optical frequency comb.

Main Results:

• Experimental demonstration of a 20 mm measurement range with approximately 10 pm resolution.
• Displacement residuals within 10 nm over the 20 mm range when compared to a heterodyne interferometer.
• Mechanical stability of the F-P cavity identified as the primary limitation on resolution.

Conclusions:

• The developed DRT F-P interferometer system enables high-resolution, long-range absolute displacement metrology.
• This technology shows promise for precision length metrology applications, including Watt balance and Joule balance projects.
• The system offers a traceable and nonlinear-free method for critical scientific measurements.