Demonstration of an ultra-low-threshold phonon laser with couple...

We demonstrate an ultra-low-threshold phonon laser using a coupled-microtoroid-cavity system by introducing a novel coupling approach. The scheme exhibits both high optical quality factors and high mechanical quality factors. We have experimentally obtained the mechanical quality factor up to 18,000 in vacuum for a radialbreathing mode of 59.2 MHz. The measured phonon lasing threshold is as low as 1.2 μW, which is ～5 times lower than the previous result.2017-1-12017-2-9