Linewidth and Chirp of MEMS-VCSELs

This letter analyzes the influence of micromachined Bragg mirrors within active Fabry-Perot cavities on basic laser characteristics, like linewidth and chirp. The impact of thermal noise of the micromechanic structure is discussed and its influence on the linewidth of a microelectromechanical system (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) is verified in an experiment. For the first time, we demonstrate for a MEMS-VCSEL a record low average linewidth of 210 MHz and extract an intrinsic linewidth of below 30 MHz. The second issue deals with the influence of microforces like radiation pressure, radiometric pressure, and length extension of the Bragg-mirror structure due to absorption on the chirp behavior of a MEMS-laser. For the first time, these effects and their influence on the VCSEL dynamics are modelled and discussed in detail. Further, the measured chirp characteristics are analyzed and compared with our modelling to quantify the influence of above effects on the device characteristics