Low-Voltage, Coupled Multiple Quantum Well Electroreflective Modulators towards Ultralow Power Inter-Chip Optical Interconnects

An electroreflective modulator based on multiple-pass electroabsorption (EA) of coupled multiple quantum wells (CMQWs) is demonstrated for integration with low-loss polymer optical waveguides towards inter-chip and on-board optical interconnects at 850 nm. Taking advantage of coupling between quantum states in MQWs, the top polymer cladding and the bottom Au mirror form a Fabry–Perot cavity to further enhance the EA of CMQWs, thereby greatly improving the extinction ratio (ER) at a low voltage. The device achieves an ER of ∼6 dB and an insertion loss (IL) <3 dB at 2 V, notably outperforming conventional surface-incident EA modulators at the same driving voltage. A further optimized modulator design can achieve a peak ER of 9–12 dB at 2 V with a low IL of 2–3 dB and a relatively broad spectral bandwidth of ∼10 nm. The low capacitance and reverse bias operation at a low voltage potentially offer ∼10× lower power consumption compared to direct modulation of 850 nm lasers. This simple surface-incident CMQW modulator is a promising candidate for integration with ultralow power inter-chip and on-board interconnect architectures.