Influence of optical feedback-induced phase on turn-on dynamics of vertical-cavity surface-emitting semiconductor lasers

We report on experimental and theoretical study of the influence of optical feedback-induced phase change on both the coupled optical power from GaAs based VCSEL into a multimode fiber under continuous wave operation and the turn-on dynamics under current modulation. A standing-wave interference pattern of laser light between the fiber facet and the VCSEL top mirror generates external optical feedback to the VCSEL, The phase variation of the feedback light changes the threshold gain periodically with a half-wavelength period. When the fiber is located at maxima and minima of this pattern, it causes a change of 50 μA in the threshold current under continuous wave (CW) operation. Thin change of threshold current induces a change in the turn-on delay time by 50 ps under bias-free pulsed operation.