# Subdiffraction incoherent optical imaging via spatial-mode demultiplexing: semiclassical treatment

## TL;DR

This paper provides a semiclassical analysis of a spatial-mode demultiplexing (SPADE) scheme for far-field incoherent optical imaging, demonstrating its superior accuracy over direct imaging in estimating moments of subdiffraction objects.

## Contribution

It generalizes SPADE for various point-spread functions and evaluates its error performance in estimating object moments under realistic noise conditions.

## Key findings

- SPADE outperforms direct imaging in estimating higher-order moments.
- The analysis applies to a broad class of point-spread functions.
- SPADE achieves lower estimation errors near the diffraction limit.

## Abstract

I present a semiclassical analysis of a spatial-mode demultiplexing (SPADE) measurement scheme for far-field incoherent optical imaging under the effects of diffraction and photon shot noise. Building on previous results that assume two point sources or the Gaussian point-spread function, I generalize SPADE for a larger class of point-spread functions and evaluate its errors in estimating the moments of an arbitrary subdiffraction object. Compared with the limits to direct imaging set by the Cram\'er-Rao bounds, the results show that SPADE can offer far superior accuracy in estimating the second and higher-order moments.