Realization of efficient electroabsorption using intersubband transitions in step quantum wells

We have demonstrated efficient intersubband electroabsorption in InGaAs/InAlGaAs/InAlAs step quantum wells grown by metal-organic vapor phase epitaxy (MOVPE). An absorption modulation of 6 dB at $\lambda =6.0\mu$m due to Stark shift of the IS absorption was achieved at a low voltage swing of $\pm 0.5$ V in a multipass waveguide structure. Based on the experimental results it is estimated that an electroabsorption modulator with a low peak-to-peak voltage of $V_{pp}=0.9$ V can yield a modulation speed of $f_{3dB}\approx 120$ GHz with the present material by using a strongly confining surface plasmon waveguide of 30 $\mu$m length.