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Proceedings Paper

Highly efficient polarization-selective out-coupling of harmonic light in birefringent WGM resonators (Conference Presentation)
Author(s): Luke S. Trainor; Florian Sedlmeir; Christian Peuntinger; Harald G. L. Schwefel

Paper Abstract

The strong confinement obtained in whispering gallery mode (WGM) resonators is highly conducive to nonlinear effects, due to both resonant enhancement of the fields and a large modal overlap. This confinement can, however, also lead to difficulties; it is difficult to efficiently pump the nonlinear interaction whilst also extracting the signal light, especially when very different wavelengths are involved. The common coupling mechanisms to WGM resonators are all evanescent, and the coupling rates inherit the exponential decay of the evanescent field. The decay length of these fields is proportional to the wavelength, so longer wavelength modes will tend to couple more than their shorter counterparts. Experimentally this hinders efficiency and, by extension, observation of nonlinear processes. Through the use of a birefringent prism, and the different phase-matching conditions it imposes on coupling orthogonally-polarized modes, we can independently control the coupling rates of a pump mode and its second harmonic in an x-cut lithium niobate resonator. We thereby critically couple pump and signal in kind, increasing the process’s efficiency fifteen-fold. This selective coupling can easily be applied to birefringent resonators, where the birefringence is large enough, through use of a prism of the same material. This can also be used with isotropic media, if a suitable birefringent material can be found.

Paper Details

Date Published: 14 March 2018
Proc. SPIE 10518, Laser Resonators, Microresonators, and Beam Control XX, 105180L (14 March 2018); doi: 10.1117/12.2295863
Show Author Affiliations
Luke S. Trainor, Univ. of Otago (New Zealand)
Florian Sedlmeir, Max-Planck-Institut für die Physik des Lichts (Germany)
Univ. of Otago (New Zealand)
Christian Peuntinger, Univ. of Otago (New Zealand)
Harald G. L. Schwefel, Univ. of Otago (New Zealand)

Published in SPIE Proceedings Vol. 10518:
Laser Resonators, Microresonators, and Beam Control XX
Alexis V. Kudryashov; Alan H. Paxton; Vladimir S. Ilchenko, Editor(s)

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