Optimum Small Optical Beam Displacement Measurement

TL;DR

This paper derives the quantum noise limit for optical beam displacement measurement, showing that a new homodyne detection scheme with TEM10 mode outperforms traditional split detection, especially when using squeezed light.

Contribution

It introduces an optimal displacement measurement scheme using TEM10 homodyne detection, surpassing split detection in efficiency and performance.

Findings

The quantum noise limit for beam displacement is derived.

The proposed TEM10 homodyne scheme outperforms split detection.

Squeezed light enhances measurement sensitivity in both schemes.

Abstract

We derive the quantum noise limit for the optical beam displacement of a TEM00 mode. Using a multimodal analysis, we show that the conventional split detection scheme for measuring beam displacement is non-optimal with 80% efficiency. We propose a new displacement measurement scheme that is optimal for small beam displacement. This scheme utilises a homodyne detection setup that has a TEM10 mode local oscillator. We show that although the quantum noise limit to displacement measurement can be surpassed using squeezed light in appropriate spatial modes for both schemes, the TEM10 homodyning scheme out-performs split detection for all values of squeezing.