Spatial-mode Demultiplexing Research Articles

Conservative classical and quantum resolution limits for incoherent imaging

I propose classical and quantum limits to the statistical resolution of two incoherent optical point sources from the perspective of minimax parameter estimation. Unlike earlier results based on the Cramér-Rao bound (CRB), the limits proposed here, based on the worst-case error criterion and a Bayesian version of the CRB, are valid for any biased or unbiased estimator and obey photon-number scalings that are consistent with the behaviours of actual estimators. These results prove that, from the minimax perspective, the spatial-mode demultiplexing measurement scheme recently proposed by Tsang, Nair, and Lu [Phys. Rev. X 2016, 6 031033.] remains superior to direct imaging for sufficiently high photon numbers.

Spatial mode demultiplexing technique using angularly multiplexed volume holograms with a phase plate

In this paper, we propose a spatial mode demultiplexing technique that uses a volume holographic demultiplexer (VHDM) with a phase plate. The VHDM can separate the multiplexed spatial modes with a single device by using angularly multiplexed volume holograms. In the VHDM, modal cross-talks, which are called inter-page cross-talks in the holographic data storages, are generated, and hence the separation performance of the VHDM is degraded by the intensity overlap between spatial modes. Therefore, we propose a novel scheme wherein phase modulation with a phase plate is added to the conventional scheme. The proposed scheme can achieve high separation performance by modulating the phase of spatial modes to reduce the intensity overlap. In this study, we demonstrated the basic operation of the proposed method for a specific linearly polarized mode group. The separation performance of the VHDM was observed to be markedly improved by the proposed method.

Subdiffraction incoherent optical imaging via spatial-mode demultiplexing

I propose a spatial-mode demultiplexing (SPADE) measurement scheme for the far-field imaging of spatially incoherent optical sources. For any object too small to be resolved by direct imaging under the diffraction limit, I show that SPADE can estimate its second or higher moments much more precisely than direct imaging can fundamentally do in the presence of photon shot noise. I also prove that SPADE can approach the optimal precision allowed by quantum mechanics in estimating the location and scale parameters of a subdiffraction object. Realizable with far-field linear optics and photon counting, SPADE is expected to find applications in both fluorescence microscopy and astronomy.