Performance of strained InGaAs/InAlAs multiple-quantum-well electroabsorption modulators

The performance of a strained InGaAs/InAlAs multiple-quantum-well (MQW) electroabsorption (EA) modulator was evaluated theoretically and experimentally, The theoretical analysis showed that adding tensile strain to the InGaAs wells widens the wells and reduces the driving voltage; it also showed that adding compressive strain to the InAlAs barriers reduces the band discontinuities and increases the optical saturation power. A fabricated InGaAs/InAlAs MQW modulator with tensile strain in the wells and compressive strain in the barriers had a large modulation bandwidth (f_{3 dB}>20 GHz) and a lower driving voltage (V_{15 dB}=1.2 V) compared to an unstrained InGaAs/InAlAs MQW modulator, so it had a higher modulation efficiency (17 GHz/V). This strained MQW modulator produced a 10 Gb/s optical signal with a clear eye opening and small chirping (α_eff=0.6). Moreover, it had shorter carrier escape times, so it has better optical saturation behavior. Introducing strain thus significantly improves the performance of the MQW-EA modulators