A rapid nanometre-precision autocorrelator

TL;DR

This paper introduces a rapid autocorrelator technique capable of achieving approximately 30 nm depth resolution per pixel in 30 seconds, utilizing statistical estimation and sCMOS camera imaging for high-precision measurements.

Contribution

The paper presents a novel method combining nonlinear optics, statistical estimation, and camera imaging to achieve nanometre-precision depth measurements rapidly.

Findings

Achieves ~30 nm depth resolution in 30 seconds per pixel.

Standard error of delay measurement falls below 1 nm after 30 seconds.

Numerical simulations confirm near shot-noise-limited precision.

Abstract

The precise measurement of a target depth has applications in biophysics and nanophysics, and non-linear optical methods are sensitive to intensity changes on very small length scales. By exploiting the high sensitivity of an autocorrelator's dependency on path length, we propose a technique that achieves $\approx$30 nm depth resolution for each pixel in 30 seconds. Our method images up-converted pulses from a non-linear crystal using a sCMOS camera and converts the intensity recorded by each pixel to a delay. By utilising statistical estimation theory and using the data from a set of 32$\times$32 pixels, the standard error of the detected delay falls below 1 nm after 30 seconds of measurement. Numerical simulations show that this result is extremely close to what can be achieved with a shot-noise-limited source and is consistent with the precision that can be achieved with a sCMOS camera.