Effect of internal optical loss on the modulation bandwidth of a quantum dot laser

Abstract

We show that the internal optical loss, which increases with free-carrier density in the waveguide region, considerably reduces the modulation bandwidth ω−3 dB of a quantum dot laser. At a certain optimum value j0opt of the dc component of the injection current density, the maximum bandwidth ω-3dBmax is attained and the modulation response function becomes as flat as possible. With internal loss cross-section σint increasing and approaching its maximum tolerable value, ω-3dBmax decreases and becomes zero. As with j0opt, there also exists the optimum cavity length, at which ω−3 dB is highest; the larger is σint, the longer is the optimum cavity.

Effect of excited states on the ground-state modulation bandwidth in quantum dot lasers

“…Several factors can affect the dynamic properties of QD lasers and limit the modulation bandwidth. Among such factors are the carrier capture delay from the higher-dimensionality reservoir regions (2D wetting layer [4][5][6][7] and bulk optical confinement layer (OCL) 8 ) into QDs, the internal optical loss, which increases with carrier density in the OCL, 9 and the gain compression (see, e.g., Ref. 10).…”