Experimental realization of deep sub-wavelength confinement of light in a topology-optimized InP nanocavity

We experimentally demonstrate an InP nanocavity with a mode volume of 0.26 (lambda/2n)3. This is an order of magnitude smaller than the mode volumes previously demonstrated in photonic crystal point-defect cavities realized in III-V materials and four times smaller than what is often referred to as the diffraction-limited volume, V lambda= (lambda/2n)3. The nanocavity is designed using topology optimization, taking into account fabrication limitations, which are pushed compared to the state-of-the-art. This work thus introduces a new class of cavities featuring extreme dielectric confinement (EDC) into the realm of III-V semiconductors, offering order-of-magnitude Purcell-enhancement of the radiative rate. EDC nanocavities may thus be employed to significantly improve the properties of nanolasers, nanoLEDs and single-photon sources, among other applications.