Balanced detection for interferometry with a noisy source

Area of Science:

• Optics and photonics
• Nanotechnology
• Metrology

Background:

• Optical properties of nanostructures are contingent upon their size, shape, material composition, and surrounding environment.
• Interferometry, utilizing a broadband light source, is a key technique for probing these optical characteristics.
• A significant limitation in current interferometric measurements is the intrinsic noise associated with broadband supercontinuum sources, which compromises measurement sensitivity.

Purpose of the Study:

• To introduce and evaluate an auto-balancing technique for mitigating noise in broadband supercontinuum sources.
• To enhance the signal-to-noise ratio (SNR) of these sources for improved interferometric measurements.
• To demonstrate the capability of detecting extremely low optical powers with high sensitivity.

Main Methods:

• Implementation of an auto-balancing technique applied to a broadband supercontinuum light source.
• Characterization of noise reduction achieved by the auto-balancing method.
• Interferometric detection of low optical power signals using the noise-reduced source.

Main Results:

• Demonstrated a substantial noise reduction of 41 dB in the broadband supercontinuum source.
• Achieved a significant increase in the signal-to-noise ratio.
• Enabled interferometric detection of optical powers as low as 0.01 picowatts (pW).
• Confirmed successful detection within a short integration time of 5 milliseconds.

Conclusions:

• The auto-balancing technique effectively suppresses noise in broadband supercontinuum sources.
• This noise reduction significantly enhances measurement sensitivity, allowing for the detection of minute optical powers.
• The method holds promise for advancing precision measurements in nanostructure characterization and other optical sensing applications.