Gain dynamics in a highly ytterbium-doped potassium double tungstate thin-film amplifier

Yean Sheng Yong, Shanmugam Aravazhi, Sergio A. Vázquez-Córdova, Jennifer L. Herek, Sonia M. García-Blanco, Markus Pollnau

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Abstract

Active media with high rare-earth concentrations are essential for small-footprint waveguide amplifiers. When operating at high population inversion, such devices are often affected by undesired energy-transfer processes and thermal effects. In this work, we study a 32-μm-thick epitaxial layer of potassium gadolinium ytterbium double tungstate with a high Yb content of 57at.%, representing an Yb3+ concentration of ∼3.8 × 1021 per cubic centimeter, grown onto an un-doped KY(WO4)2 substrate. The pump absorption, luminescence decay, and small-signal gain are investigated under intense pumping conditions. Spectroscopic signatures of an energy-transfer process and of quenched ions, as well as thermal effects are observed. We present a gain model which takes into account excessive heat generated due to the abovementioned experimental observations. Based on finite-element calculations, we find that the net gain is significantly reduced due to, firstly, a fraction of Yb3+ ions not contributing to stimulated emission, secondly, a reduction of population inversion owing to a parasitic energy-transfer process and, thirdly, degradation of the effective transition cross-sections owing to device heating. Nevertheless, a signal enhancement of 8.1 dB was measured from the sample at 981 nm wavelength when pumping at 932 nm. The corresponding signal net gain of ∼800 dB/cm, which was achieved without thermal management, is promising for waveguide amplifier operating without active cooling.

Original languageEnglish
Title of host publicationSolid State Lasers XXVIII
Subtitle of host publicationTechnology and Devices
EditorsW. Andrew Clarkson, Ramesh K. Shori
PublisherSPIE
Volume10896
ISBN (Electronic)9781510624344
DOIs
Publication statusPublished - 1 Jan 2019
EventSolid State Lasers XXVIII: Technology and Devices 2019 - San Francisco, United States
Duration: 5 Feb 20197 Feb 2019
Conference number: 28

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume10896
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X

Conference

ConferenceSolid State Lasers XXVIII: Technology and Devices 2019
CountryUnited States
CitySan Francisco
Period5/02/197/02/19

Keywords

  • Integrated optics materials
  • Optical amplifiers
  • Rare-earth-doped materials
  • Ytterbium lasers

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