Low-coherence heterodyne interferometry using an achromatic frequency shifter based on a frequency-domain optical...

Area of Science:

• Optical Physics
• Metrology
• Interferometry

Background:

• Low-coherence interferometry is crucial for precise measurements.
• Conventional homodyne interferometry faces limitations in signal-to-noise ratio.
• Heterodyne interferometry offers potential for signal enhancement.

Purpose of the Study:

• To develop a high-sensitivity low-coherence heterodyne interferometric system.
• To improve the signal-to-noise ratio (SNR) in low-coherence measurements.
• To demonstrate the effectiveness of a tandem Michelson interferometer configuration.

Main Methods:

• A novel system using two tandem polarizing Michelson interferometers.
• Incorporation of a compact frequency-domain optical delay line.
• Utilized a lock-in amplifier for fringe amplitude and phase detection.
• Achieved a wavelength-independent 4.4 kHz frequency shift using a zero-group-delay configuration.

Main Results:

• The proposed heterodyne system achieved a signal-to-noise ratio over 30-fold higher than conventional homodyne methods.
• Demonstrated high sensitivity in low-coherence measurements.
• Verified the wavelength-independent frequency shift capability.

Conclusions:

• The developed high-sensitivity low-coherence heterodyne interferometric system offers significant advantages.
• The tandem Michelson interferometer design with a frequency-domain delay line enhances measurement precision.
• This technique provides a substantial improvement for applications requiring sensitive low-coherence measurements.