Graphene Q-switched Yb:Yttria waveguide laser by evanescent-field interaction delivering an average output power of 0.5 W

Abstract

Pulsed waveguide lasers are interesting sources for a wide range of applications ranging from medicine, industrial processing and defence. Waveguides offer monolithic integrated structures with a natural geometric compatibility with high-power diode laser pump sources allowing compact devices. Additionally, if propagation losses can be kept low, the optical confinement can lead to low laser thresholds, high efficiencies, and low power requirements for passive Q-switching or mode-locking via saturable absorbers (SAs). Rare-earth-doped sesquioxide materials, such as yttria, possess physical and spectroscopic properties that make them very interesting for high-power solid-state lasers, and we have recently reported Q-switched operation of a pulsed laser deposited (PLD)-grown Yb:Y₂O₃ waveguide using a graphene-covered output coupler as an SA. The output power of this laser was limited by damage to the graphene layer, which is directly in the path of the laser beam. However, waveguides also offer the opportunity of coupling the laser beam to the saturable absorber via evanescent-field coupling and this in turn offers the possibility of high-power pulsed operation.
In this paper, we demonstrate an Yb:Y₂O₃ waveguide laser Q-switched using evanescent-field interaction with graphene. 310 nJ pulses at an average power of 456 mW were obtained from a graphene-covered Yb:Y₂O₃ waveguide, which represents more than an order of magnitude improvement when compared to previous Q-switched waveguide lasers using end-butted graphene.

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Identifiers

ORCID for J.A. Grant-Jacob: orcid.org/0000-0002-4270-4247

ORCID for J.I. Mackenzie: orcid.org/0000-0002-3355-6051

ORCID for R.W. Eason: orcid.org/0000-0001-9704-2204

ORCID for D.P. Shepherd: orcid.org/0000-0002-4561-8184

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