Ultrastrong coupling between THz phonons and photons caused by an enhanced vacuum electric field

Ultrastrong Coupling Enhancement with Squeezed Mode Volume in Terahertz Nanoslots

“…There are several factors governing the ultrastrong coupling properties of a nanophotonic resonator. Figure a shows width-dependent Rabi splitting for our nanoslots, together with previous record-holding values in split-ring resonator-based systems . The experimentally obtained value of the spitting may be slightly larger than the theoretical expectation due to small differences in resonance line widths of the nanoslots.…”

“…Figure 3a shows width-dependent Rabi splitting for our nanoslots, together with previous record-holding values in split-ring resonator-based systems. 18 The experimentally obtained value of the spitting may be slightly larger than the theoretical expectation due to small differences in resonance line widths of the nanoslots. Comparing the Rabi splitting of nanoslots and split ring resonators at different gap widths, we find that the nanoslots exhibit a higher Rabi splitting than the split ring resonators.…”

“…Rabi splitting as a function of gap width in (a) linear and (b) log scales for the x axis. Blue dots denote calculated results for nanoslot structures, and green dots show previously reported values obtained from perovskite-integrated split ring resonators . The red star denotes the experimental result of this work.…”

“…Recently, organic–inorganic halide perovskites (from here perovskites) have been extensively studied as a viable platform for ultrastrong photon–phonon coupling in terahertz (THz) frequencies. Previous studies utilized perovskites coupled to split ring resonators and observed phonon–polaritons with Rabi splitting as large as Ω R = 0.26ω 0 in a 1.5 μm gap and Ω R = 0.45ω 0 in a 100 nm gap . In these works, the main strategy for increasing the coupling strength is to reduce the gap width of the split ring resonators, thereby reducing the effective mode volume.…”

“…Previous studies utilized perovskites coupled to split ring resonators and observed phonon−polaritons with Rabi splitting as large as Ω R = 0.26ω 0 in a 1.5 μm gap 17 and Ω R = 0.45ω 0 in a 100 nm gap. 18 In these works, the main strategy for increasing the coupling strength is to reduce the gap width of the split ring resonators, thereby reducing the effective mode volume. However, as the metallic gap width gets narrow, it becomes increasingly challenging to insert the perovskite into such a small gap, and the grain size of the polycrystalline perovskite may cause further complications.…”