Light-matter interaction with a Single Terahertz meta-atom

In this work, by combining an asymmetric Silicon immersion lens configuration and a complementary resonator design, far-field transmission measurement of a single subwavelength split-ring resonator, ultra-strongly coupled to inter Landau level transitions in a single quantum well, is resolved. The highest coupling is 60%, achieved for only similar to 2000 coupled electrons for a single resonator on an InSb quantum well. This technique can be useful to characterize the complex conductivity of micronsized samples, such as exfoliated graphene or transition metal dichalcogenide flakes, in the THz domain.