Intraband dynamics and terahertz emission in biased semiconductor superlattices coupled to double far-infrared pulses

This paper studies both the intraband polarization andterahertz emission of a semiconductor superlattice in combined dc andac electric fields by using the superposition of two identical timedelayed and phase shifted optical pulses. By adjusting the delaybetween these two optical pulses, our results show that theintraband polarization is sensitive to the time delay. The peakvalues appear again for the terahertz emission intensity due to thesuperposition of two optical pulses. The emission lines of terahertzblueshift and redshift in different ac electric fields and dynamiclocalization appears. The emission lines of THz only appear toblueshift when the biased superlattice is driven by a single opticalpulse. Due to excitonic dynamic localization, the terahertz emissionintensity decays with time in different dc and ac electric fields.These are features of this superlattice which distinguish it from asuperlattice generated by a single optical pulse to drive it.