A superresolution-enhanced spectrometer beyond the Cramer-Rao bound in phase sensitivity.

Area of Science:

• Sensing and Metrology
• Classical Optics
• Optical Spectroscopy

Background:

• Precision measurement relies on Fisher information, with the Cramer-Rao lower bound (CRLB) defining the shot-noise limit.
• Classical coherence techniques have improved resolution, but practical applications face limitations like lithography.
• Superresolution in phase sensitivity has been achieved using higher-order intensity correlations.

Purpose of the Study:

• To introduce a classical coherence technique for enhancing precision metrology in optical spectrometers.
• To demonstrate superresolution beyond the diffraction and CRLB limits.
• To provide a robust, classical alternative to quantum sensing methods.

Main Methods:

• Utilizing higher-order intensity correlations of a phase-controlled interferometer output.
• Applying superresolution principles to an optical spectrometer.
• Employing a scanning mode with fringe counting for robust performance.

Main Results:

• Achieved enhanced frequency resolution in optical spectrometers, linearly proportional to the intensity-product order.
• Demonstrated a method that overcomes the Cramer-Rao lower bound (CRLB).
• Showcased a purely classical technique robust against environmental noise.

Conclusions:

• The developed coherence technique offers a novel approach to precision metrology, surpassing classical limits.
• This method provides a robust and practical alternative to quantum sensing for enhanced resolution.
• The linear scalability with intensity-product order presents significant advantages for future metrology applications.