Reducing Brownian motion in an electrostatically tunable MEMS laser

Brownian motion of a tunable vertical-cavity surface-emitting lasers (VCSEL) movable microelectromechanical systems (MEMS) mirror is shown to broaden the spectral width of the laser emission line. A low-noise wavelength feedback system is presented and evaluated. This feedback system is employed to reduce measured linewidth from 1050 to 400 MHz fullwidth at half-maximum (FWHM), an improvement of 62%. The effects of device design parameters on closed-loop Brownian motion levels are analyzed. The potential increases in performance resulting from vacuum packaging and advanced controller design are discussed.