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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Imaging spatial-helical mode interference of single photons

Enrique J. Galvez, Eric G. Johnson, Benjamin J. Reschovsky, Laura E. Coyle, A. Shah

Published Jan 13, 2010• 2 citations
Publisher

Abstract

We present a study of the imaging of the interference of spatial-helical modes of single photons. This work includes a mathematical treatment that accounts for the direction of propagation and spatial mode degrees of freedom in the situation where light travels through an interferometer that prepares the light in distinct spatial modes and makes them interfere. We present results of the interference at the single photon level of the spatialhelical modes with topological charge 1 and 0. The results are consistent with the expectation that each photon carries the entire spatial mode information.

DOI
10.1117/12.843076

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We present a study of the imaging of the interference of spatial-helical modes of single photons. This work includes a mathematical treatment that accounts for the direction of propagation and spatial mode degrees of freedom in the situation where light travels through an interferometer that prepares the light in distinct spatial modes and makes them interfere. We present results of the interference at the single photon level of the spatialhelical modes with topological charge 1 and 0. The results are consistent with the expectation that each photon carries the entire spatial mode information.
We present measurements of the helical mode of single photons and do so by sending heralded photons through a Mach–Zehnder interferometer that prepares the light in a helical mode with topological charge one, and interferes it with itself in the fundamental non-helical mode. Masks placed after the interferometer were used to diagnose the amplitude and phase of the mode of the light. Auxiliary measurements verified that the light was in a non-classical state. The results are in good agreement with theory. The experiments demonstrate in a direct way that single photons carry the entire spatial helical-mode information.
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Reading quantum information of single photons is commonly realized by quantum tomography or the direct (weak) measurement approach. However, these methods are time-consuming and face enormous challenges in characterizing single photons from an ultrafast light source due to the stringent temporal mode matching requirements. Here, we retrieve the spatial wavefunction of indistinguishable single photons from both a continuous wave source and a femtosecond light source using a self-referencing interferometer. Our method only requires nine ensemble-averaged measurements. This technique simplifies the measurement procedure of single-photon wavefunction and automatically mode matches each self-interfering single photon temporally, which enables the measurement of the spatial wavefunction of single photons from an ultrafast light source.