Ultra-high Q sphere-like cavities for cascaded stimulated Brillouin lasing

High Q microsphere optical cavity is usually fabricated from a single mode fiber. Here, we propose a new method to fabricate sphere-like cavity by melting the tip of rotating quartz-rod with a CO2 laser. The cavities with diameter from 200 mu m to 700 mu m and resonant Q factors above 10(8) are obtained. Due to the rich resonances of the sphere-like cavity, up to 15-order cascaded stimulated Brillouin lasings (SBL) near 1.55 mu m are observed in a cavity with a diameter of similar to 760 mu m by simply tuning the pump wavelength to a finely-selected resonance. We wish the ultra-high Q cavities with rich resonances and bulk rod mount can have practical applications in nonlinear optics and microwave photonics as an optical component.