Epitaxial Growth and Spectroscopy of Sm³⁺:LiYF₄ Crystalline Layers for Orange Waveguide Lasers

The exceptional spectroscopic properties of trivalent samarium ions (Sm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>+) make them ideal candidates for lasers directly emitting in the visible spectral range. They exhibit multi-color emission corresponding to the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup>G<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf><inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">/2</inf> → <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup>H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</inf>(J = 5/2 - 11/2) transitions, with the most intense one terminating at the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup>H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7/2</inf> level falling in the orange at ~605 nm [1]. Orange lasers find application in flow cytometry, astronomy, and ozone gas detection. However, the development of Sm lasers is challenging due to weak absorption of Sm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>+ ions in the blue as the corresponding transitions are spin- forbidden <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\Delta S\neq 0)$</tex>. Guided-wave configurations, i.e., waveguides or fibers, can address this issue. Furthermore, they offer good pump / laser mode overlap, low laser thresholds, and improved thermal management. In the present work, we report on the Liquid Phase Epitaxy (LPE) growth and polarized spectroscopy of single-crystalline Sm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>+:LiYF<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> epitaxial layers with the goal of developing novel functional optical materials for orange waveguide lasers.