Toward a reconfigurable photonic integrated mode sorter for optomechanical sensing

Abstract

Spatial mode demultiplexing (SPADE) has recently emerged as a platform for quantum-limited measurement and control of nanomechanical resonators; however, taking full advantage of this approach requires reconfigurable coherent manipulation of multiple spatial modes. Here we introduce a reconfigurable SPADE architecture based on a free-space multi-plane light converter (MPLC) interfaced with a low-loss, tunable 3×3 Clements interferometer mesh implemented on a photonic integrated circuit (PIC). The Clements mesh implements arbitrary unitary transformations through thermo-optic phase shifting, enabling dynamic control of the relative amplitudes and phases of multiple modes within a programmable spatial-mode processor. We present initial characterization of the fabricated PIC, including waveguide propagation losses as low as ∼ 0.015 dB/cm, together with coupling loss and Mach-Zehnder interferometer performance. Finally, we analyze adaptive illumination and structured homodyne readout of a membrane resonator with a three-channel Hermite-Gauss mode transceiver, illustrating the potential of the scalable hybrid PIC-SPADE architecture for quantum-limited optomechanical sensing.