26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Characterisation of a six mode selective photonic lantern for displacement sensing of a trapped nanoparticle.

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral ANZOS | Photonics and Optics (ANZCOP)

Speaker

Benjamin Field (University of Sydney)

Description

While traditionally developed for astronomy use cases, photonic lanterns are finding use in a wider range of fields, leveraging their spatial mode demultiplexing (SPADE) capabilities.

We explore the use of mode-selective lanterns as the SPADE receiver for the displacement sensing of levitated nanoparticles [1]. When collecting the scattered light from a trapped particle, it has been shown that the center-of-mass (COM) motional degrees of freedom (DOF) couple to linearly polarized (LP) spatial modes with varying efficiency. We here study demultiplexing the scattered light into a high fidelity 6 mode photonic lantern. In particular, we are interested in
improving the measurement efficiency by increasing the number of modes. Using higher-order modes also opens the possibility to measure rotational DOF. Using photonic lanterns for dynamic imaging of nanomechanical oscillators puts new requirements on the lantern, including high power handling, temperature stability and a high fidelity breakdown into the LP mode basis.

This talk explores the characterisation of the lantern to ensure it is fit for purpose. Making phase sensitive measurements using off axis holography [2], we analyse the change in the transfer matrix as the lantern is subject to temperature changes, and high laser powers. With these characterisations completed, we assess the coupling efficiency of the various motional DOF (translational and rotational) of a levitated nanoparticle to the photonic lantern.

[1] T. J. Dinter et al., ‘Three-dimensional and selective displacement sensing of a levitated nanoparticle via spatial mode decomposition’, Phys. Rev. Res., vol. 8, no. 2, 2026, doi: 10.1103/9mnc-ddvw.

[2] A. K. Taras et al., ‘Illuminating the lantern: coherent, spectro-polarimetric characterization of a multimode converter’, Opt. Express, OE, vol. 34, no. 1, pp. 1012–1025, Jan. 2026, doi: 10.1364/OE.583186.