Efficient Electroabsorption Modulation of Mid- and Far-Infrared Radiation by Driving the Band-Inversion Transition of InAs / GaSb Type-II Quantum Wells

Abstract

Based on the self-consistent calculations of the eight-band $\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ model and Poisson equation, we theoretically demonstrate that the intersubband optical absorption of $\mathrm{In}\mathrm{As}$/$\mathrm{Ga}\mathrm{Sb}$ type-II quantum wells (QWs) is effectively tuned by the electric-field-driven band-inversion transition. By utilizing this property, $\mathrm{In}\mathrm{As}$/$\mathrm{Ga}\mathrm{Sb}$ QWs can be made into highly efficient electroabsorption modulators (EAMs) for TM-polarized mid-infrared radiation (MIR) (approximately $4.2$--$12\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$) and TE-polarized far-infrared radiation (FIR) (approximately $12$--$100\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$). At low temperature, an example $p$-$i$-$n$ waveguide EAM composed of six-period $\mathrm{In}\mathrm{As}$/$\mathrm{Ga}\mathrm{Sb}$ QWs achieves a drive voltage of $<0.5$ V, a 3-dB cutoff bandwidth of approximately $24.6$ GHz, and a dynamic power consumption of $\ensuremath{\le}\phantom{\rule{0.2em}{0ex}}0.06$ mW/GHz for a 20-dB on:off ratio modulation of $4.46$-$\ensuremath{\mu}\mathrm{m}$ TM-polarized radiation. Although the modulation efficiencies drop by 70%--80% when the temperature increases, the performance of $\mathrm{In}\mathrm{As}$/$\mathrm{Ga}\mathrm{Sb}$ EAMs is (at least) comparable with conventional $1.55$-$\ensuremath{\mu}\mathrm{m}$ EAMs at 300 K. These results suggest that $\mathrm{In}\mathrm{As}$/$\mathrm{Ga}\mathrm{Sb}$ EAMs are promising devices for high-speed and low-power-consumption MIR (or FIR) free-space optical communications.