A new microcavity featuring a subwavelength grating provides greater control over polaritons than previous techniques. Bo Zhang and co-workers from the University of Michigan, USA, and the University of Wuerzburg, Germany, fabricated a vertical semiconductor cavity in which GaAs quantum wells were sandwiched between two distributed Bragg reflectors (DBRs): a thick DBR below, and a thin DBR above. They then applied a polarization-sensitive subwavelength grating, comprising a series of slits etched into a suspended layer of Al0.15GaAs, to the top of the cavity, thus creating a top mirror with high reflectance and at the same time providing additional control over the polaritons. Their optical excitation experiments confirm that the cavity is capable of supporting low-threshold, ground-state polariton lasing at a chosen polarization. The approach potentially provides a scalable architecture for realizing coupled lattice cavity systems.
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