Photonic crystal microdisk lasers with exceptional spontaneous emission coupling to the lasing mode

A long existing issue for microdisk lasers is the small spontaneous emission coupling rate ({\beta}) in microdisk,. We found that it is due to the coupling of emitter spontaneous emission into competing Fabry-Perot (FP) modes in the microdisk cavity. Based on this analysis, we propose a new type of photonic crystal microdisk (PCM) laser to drastically suppress the photonic density of states in the vertical FP modes. As a result, we obtained a three fold increase of {\beta} than previously reported highest {\beta} of 0.15 at room temperature. The spontaneous emission control in truncated photonic crystals becomes efficient when the period number is more than one. We also demonstrate a three-stack PCM laser at low temperature with {\beta} as high as 0.72, which is 24 times higher than that in typical single microdisk (0.03), which also results in 50% threshold reduction.