Xu Linfeng, Xie Chengfeng, Wang Mengyu, Guo Zhuang, Wei Bin, Zhang Hailin, Zhang Lei, He Xingdao
Opt Express. 2023 Nov 6;31(23):38365-38375. doi: 10.1364/OE.501129.
Backward stimulated Brillouin scattering (SBS) in optical microcavities has been widely used in nonlinear optics and microwave photonics. Compared with glass material microcavity, magnesium fluoride crystal microcavity has the advantages of small absorption coefficient, fewer defects and larger nonlinear coefficient, moreover, it usually has a narrow gain bandwidth of tens of megahertz. Here, we design a high precision machining system to produce ultra-smooth surface magnesium fluoride crystal disk cavities with a diameter of about 5 mm, Q value exceeding 10, FSR matching material Brillouin gain. By simply modulating the pump wavelength and coupling power, we observe SBS phenomena with a 13.47 GHz Brillouin frequency shift near 1.55µm and cascaded stimulated Brillouin lasers (SBL) of up to 12 orders. In addition, the Brillouin-Kerr optical frequency comb in this device is demonstrated, observing nearly 300 comb lines spanning across a spectral window of 250 nm. Our research provides a way to fabricate high-Q crystal microcavities and demonstrates the potential of these devices in applications such as microwave sources and nonlinear optics.
光学微腔中的后向受激布里渊散射（SBS）已在非线性光学和微波光子学中得到广泛应用。与玻璃材料微腔相比，氟化镁晶体微腔具有吸收系数小、缺陷少和非线性系数大的优点，此外，它通常具有几十兆赫兹的窄增益带宽。在此，我们设计了一种高精度加工系统，以生产直径约5毫米、品质因数超过10、自由谱范围匹配材料布里渊增益的超光滑表面氟化镁晶体盘形腔。通过简单地调制泵浦波长和耦合功率，我们观察到在1.55µm附近具有13.47 GHz布里渊频移的SBS现象以及高达12阶的级联受激布里渊激光器（SBL）。此外，还展示了该器件中的布里渊 - 克尔光学频率梳，观察到跨越250 nm光谱窗口的近300条梳状线。我们的研究提供了一种制造高Q值晶体微腔的方法，并展示了这些器件在微波源和非线性光学等应用中的潜力。
