Limitations to the determination of a Laguerre–Gauss spectrum via projective, phase-flattening measurement

Qassim, H., Miatto, F. M., Torres, J. P., Padgett, M. J. , Karimi, E. and Boyd, R. W. (2014) Limitations to the determination of a Laguerre–Gauss spectrum via projective, phase-flattening measurement. Journal of the Optical Society of America B: Optical Physics, 31(6), A20-A23. (doi:10.1364/JOSAB.31.000A20)

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Publisher's URL: http://dx.doi.org/10.1364/JOSAB.31.000A20

Abstract

One of the most widely used techniques for measuring the orbital angular momentum (OAM) components of a light beam is to flatten the spiral phase front of a mode, in order to couple it to a single-mode optical fiber (SMOF). This method, however, suffers from an efficiency that depends on the OAM of the initial mode and on the presence of higher-order radial modes. The reason is that once the phase has been flattened, the field retains its ringed intensity pattern and is therefore a nontrivial superposition of purely radial modes, of which only the fundamental one couples to a SMOF. In this paper, we study the efficiency of this technique both theoretically and experimentally. We find that even for low values of the OAM, a large amount of light can fall outside the fundamental mode of the fiber, and we quantify the losses as functions of the waist of the coupling beam of the OAM and radial indices. Our results can be used as a tool to remove the efficiency bias where fair-sampling loopholes are not a concern. However, we hope that our study will encourage the development of better detection methods of the OAM content of a beam of light.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Boyd, Professor Robert and Padgett, Professor Miles
Authors: Qassim, H., Miatto, F. M., Torres, J. P., Padgett, M. J., Karimi, E., and Boyd, R. W.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Journal of the Optical Society of America B: Optical Physics
Publisher:Optical Society of America
ISSN:0740-3224
ISSN (Online):1520-8540

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