Measurement of the radial mode spectrum of photons through a phase-retrieval method

Abstract

We propose and demonstrate a simple and easy-to-implement projective-measurement protocol to determine the radial index 'p' of a Laguerre-Gaussian (LGlp) mode. Our method entails converting any specified high-order LG0p mode into a near-Gaussian distribution that matches the fundamental mode of a single-mode fiber (SMF) through the use of two phase-screens (unitary transformations) obtained by applying a phase-retrieval algorithm. The unitary transformations preserve the orthogonality of modes and guarantee that our protocol can, in principle, be free of crosstalk. We measure the coupling efficiency of the transformed radial modes to the SMF for different pairs of phase-screens. Because of the universality of phase-retrieval methods, we believe that our protocol provides an efficient way of fully characterizing the radial spatial profile of an optical field.

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Cited by in corpus (4)

• Using all transverse degrees of freedom in quantum communications based on a generic mode sorter
• Near-perfect measuring of full-field transverse-spatial modes of light
• An experimental technique for measuring radial coherence
• Entangled ripples and twists of light: Radial and azimuthal Laguerre-Gaussian mode entanglement