Harmonics-assisted optical phase amplifier

TL;DR

This paper introduces a harmonic generation-based phase amplifier that coherently amplifies phase differences in optical signals, offering a practical and efficient alternative to NOON state methods for high-precision measurements.

Contribution

The paper proposes and demonstrates a novel phase amplification scheme using cascaded harmonic generation, which is more feasible and robust than NOON state-based methods.

Findings

Achieved fourfold phase amplification using cascaded second-harmonic generation.

Demonstrated the potential for recycling amplification processes for higher gains.

Showed advantages over NOON state methods in optical phase measurement.

Abstract

The change in the relative phase between two light fields serves as a basic principle for the measurement of the physical quantity that guides this change. It would therefore be highly advantageous if the relative phase could be amplified to enhance the measurement resolution. One well-known method for phase amplification involves the use of the multi-photon number and path entangled state known as the NOON state; however, a high-number NOON state is very difficult to prepare and is highly sensitive to optical losses. Here we propose and experimentally demonstrate in principle a phase amplifier scheme with the assistance of a harmonic generation process. The relative phase difference between two polarization modes in a polarized interferometer is amplified coherently four times with cascaded second-harmonic generation processes. We demonstrate that these amplification processes can be recycled and therefore have the potential to realize much higher numbers of multiple amplification steps. The phase amplification method presented here shows considerable advantages over the method based on NOON states and will be highly promising for use in precision optical measurements.