A novel all-fiber saturable absorber based on a dysprosium-doped silica fiber for more robust midinfrared pulsed fiber lasers

Description

In the last decades, there is a high interest in monitoring greenhouse gases emissions from the permafrost thawing, in particular methane and carbon dioxide, to better understand and predict the impacts of the climate change. The existing devices and methods to quantify those gases are either expensive and hard to deploy but can take measurements on a long period of time, such as Eddy towers, or time consuming since an operator must be on site to operate and measure the gas fluxes, with a closed flux chamber, for example. So, there is a high demand for novel, reliable and user-friendly devices to quantify those gases on a long period of time at a high enough frequency for an affordable price to be able to take more measurements overtime and to get a better overview of the climate change that is occurring, especially in Quebec's North. Optical spectroscopy over the thawing permafrost, thermokarts and over lakes would make a good alternative to current technologies to improve the quantity of measurements overtime while enhancing the spatial resolution of the measurements compared to Eddy towers. It also requires less operator time than flux chambers because the measurements can be fully automated.To make reliable spectroscopy measurement on an open path in any lighting conditions, a powerful enough and efficient light source, such as a fiber laser, is required. A mid-infrared fiber laser can be used to efficiently probe methane concentrations since the fundamental absorption peak of this gas is centered around a wavelength of 3.3 μm. However, because the lack of fiberized components, novel fiber components must be developed to improve the robustness of such lasers before they can safely be deployed in remote, uncontrolled environments such as the Arctic.In this presentation, we will introduce a new all-fiber saturable absorber (SA) based on a dysprosium-doped silica fiber that is more robust than previous mid-infrared SA, and thus improves the robustness and reliability of the whole laser system, since there is no need for any free space coupling of signals into the small core optical fiber. We also demonstrate an easy to use, robust and reliable Q-switched all-fiber laser emitting at 2.8 μm based on this novel SA. Furthermore, the physics applying to this saturable absorber might also apply to other rare-earth dopants in silica to provide fiberized saturable absorbers optimized for other wavelengths as well.

Abstract

International audience

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