Magnesium Fluoride Brillouin and Raman Microlaser
Jingyi Tian, Guoping Lin
Abstract
Stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) are essential light-matter interactions in materials and play a crucial role in various laser applications. In this letter, we fabricated a z-cut magnesium fluoride (MgF <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{2}$</tex-math></inline-formula> ) crystalline whispering gallery mode (WGM) microcavity with a radius of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$180$</tex-math></inline-formula> μm and quality factors ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> ) exceeding 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{8}$</tex-math></inline-formula> at 1550 nm. SBS and SRS lasing were demonstrated using this high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> MgF <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{2}$</tex-math></inline-formula> microcavity. The Brillouin frequency shift lies within the calculated broadened gain window, while the Raman frequency shift matches the A1g symmetric stretching vibration mode. By employing an excitation mapping method, we investigated the dynamics of SBS and SRS lasing together with four-wave mixing as the frequency detuning between the pump laser and the cavity resonance was varied. Our results reveal rich nonlinear frequency conversion phenomena enabled by the MgF <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{2}$</tex-math></inline-formula> microcavity, and highlight its potential for compact microlasers and sensors.