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Method for generating high purity Laguerre-Gaussian modes

Method for generating high purity Laguerre-Gaussian modes
Method for generating high purity Laguerre-Gaussian modes
Generation of a donut-shaped first-order Laguerre-Gaussian (LG01) vortex mode via a method designed to yield high mode purity is reported. Our approach utilises a novel twin-spot end-pumping scheme to directly excite the first order Hermite-Gaussian (HG01) mode in a solid-state laser, followed by a novel astigmatic mode converter based on spherical (concave) mirrors aligned at oblique incidence. A simple theoretical model for the mode converter is derived and from this the design approach is explained along with the potential benefits compared to conventional schemes based cylindrical-lens astigmatic mode converters, particularly for power scaling. As a proof-of-principle and to confirm the benefits of this scheme in terms of high mode purity we have applied it to an end-pumped Nd:YVO4 laser to generate a (LG01) beam with a controllable sense of azimuthal phase and hence orbital angular momentum. A method for characterising the resulting beam based on analysis of the spiral interference pattern derived with the aid of a Mach-Zehnder interferometer is described and yields a value for the LG01 mode purity of 94%. Common sources of mode impurity are identified and the prospects for scaling to higher power whilst maintaining high mode purity are considered.
Laser modes, solid-state lasers
0018-9197
1-9
Clarkson, W.A.
3b060f63-a303-4fa5-ad50-95f166df1ba2
Uren, Robin
409f690c-eb0b-42cb-b1b7-3d334211235e
Smith, Callum
3fc58a4e-ecd6-455e-840b-275efa52fba1
Beecher, Stephen J.
b3664adc-d6b5-4a5a-a09a-8e1415c6d3f5
Clarkson, W.A.
3b060f63-a303-4fa5-ad50-95f166df1ba2
Uren, Robin
409f690c-eb0b-42cb-b1b7-3d334211235e
Smith, Callum
3fc58a4e-ecd6-455e-840b-275efa52fba1
Beecher, Stephen J.
b3664adc-d6b5-4a5a-a09a-8e1415c6d3f5

Clarkson, W.A., Uren, Robin, Smith, Callum and Beecher, Stephen J. (2019) Method for generating high purity Laguerre-Gaussian modes. IEEE Journal of Quantum Electronics, 55 (5), 1-9. (doi:10.1109/JQE.2019.2931006).

Record type: Article

Abstract

Generation of a donut-shaped first-order Laguerre-Gaussian (LG01) vortex mode via a method designed to yield high mode purity is reported. Our approach utilises a novel twin-spot end-pumping scheme to directly excite the first order Hermite-Gaussian (HG01) mode in a solid-state laser, followed by a novel astigmatic mode converter based on spherical (concave) mirrors aligned at oblique incidence. A simple theoretical model for the mode converter is derived and from this the design approach is explained along with the potential benefits compared to conventional schemes based cylindrical-lens astigmatic mode converters, particularly for power scaling. As a proof-of-principle and to confirm the benefits of this scheme in terms of high mode purity we have applied it to an end-pumped Nd:YVO4 laser to generate a (LG01) beam with a controllable sense of azimuthal phase and hence orbital angular momentum. A method for characterising the resulting beam based on analysis of the spiral interference pattern derived with the aid of a Mach-Zehnder interferometer is described and yields a value for the LG01 mode purity of 94%. Common sources of mode impurity are identified and the prospects for scaling to higher power whilst maintaining high mode purity are considered.

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More information

In preparation date: 5 March 2019
Submitted date: 5 March 2019
Accepted/In Press date: 12 July 2019
e-pub ahead of print date: 25 July 2019
Published date: October 2019
Keywords: Laser modes, solid-state lasers

Identifiers

Local EPrints ID: 433777
URI: https://eprints.soton.ac.uk/id/eprint/433777
ISSN: 0018-9197
PURE UUID: 662ac586-96e1-48f8-8e17-cb05325bc85d

Catalogue record

Date deposited: 03 Sep 2019 16:30
Last modified: 01 Oct 2019 16:31

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Contributors

Author: W.A. Clarkson
Author: Robin Uren
Author: Callum Smith
Author: Stephen J. Beecher

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