High-speed modulation and switching characteristics ofIn(Ga)As-Al(Ga)As self-organized quantum-dot lasers

摘要

The dynamic characteristics, and in particular the modulationnbandwidth, of high-speed semiconductor lasers are determined bynintrinsic factors and extrinsic parameters. In particular, carrierntransport through the heterostructure and thermalization, or quantumncapture in the gain region, tend to play an important role. We have madena detailed study of carrier relaxation and quantum capture phenomena innIn(Ga)As-Al(Ga)As self-organized quantum dots (QD's) and single-modenlasers incorporating such dots in the gain region through a variety ofnmeasurements. The modulation bandwidth of QD lasers is limited to 5-6nGHz at room temperature and increases to ~30 GHz only upon lowering thentemperature to 100 K. This behavior is explained by consideringnelectron-hole scattering as the dominant mechanisms of electronnrelaxation in QD's and the scattering rate seems to decrease withnincrease of temperature. The switching of the emission wavelength, fromnthe ground state to an excited state, has been studied in coupled cavityndevices. It is found that the switching speed is determinednintrinsically by the relaxation time of carriers into the QD states.nFast switching from the ground to the excited state transition isnobserved. The electrooptic coefficients in the dots have been measurednand linear coefficient Τ=2.58×10-11 m/V. Thencharacteristics of electrooptic modulators (EOM's) are also described