Real-time superresolution interferometric measurement enabled by structured nonlinear optics

TL;DR

This paper introduces a real-time superresolution interferometric measurement technique using structured nonlinear optics, overcoming traditional wavelength limits and enabling practical, high-precision measurements with bright beams and low-cost detectors.

Contribution

The authors demonstrate a novel method employing structured nonlinear optics for superresolution interferometry, achieving high photon de Broglie wavelength resolution in real time.

Findings

Achieved up to 12-photon de Broglie wavelength resolution.

Demonstrated real-time superresolution measurement with high visibility.

Used low-cost detectors with bright sensing beams.

Abstract

Optical interferometers are pillars of modern precision metrology, but their resolution is limited by the wavelength of the light source, which cannot be infinitely reduced. Magically, this limitation can be circumvented by using an entangled multiphoton source because interference produced by an N-photon amplitude features a reduced de Broglie wavelength {\lambda}/N. However, the extremely low efficiency in multiphoton state generation and coincidence counts actually negates the potential of using multiphoton states in practical measurements. Here, we demonstrate a novel interferometric technique based on structured nonlinear optics, i.e., parametric upconversion of a structured beam, capable of superresolution measurement in real time. The main principle relies in that the orbital angular momentum (OAM) state and associated intramodal phase within the structured beam are both continuously multiplied in cascading upconversion to mimic the superresolved phase evolution of a multiphoton amplitude. Owing to the use of bright sensing beams and OAM mode projection, up to a 12-photon de Broglie wavelength with almost perfect visibility is observed in real time and, importantly, by using only a low-cost detector. Our results open the door to real-time superresolution interferometric metrology and provide a promising way toward multiphoton superiority in practical applications.