Experimental Realization of Extreme Light Confinement in an InP Nanocavity

Strong spatial confinement of light in a semiconductor cavity is of significant interest for enhancing the interaction between light and matter, with important applications in integrated photonics and quantum technology. Until recently, it was held by the community that in a semiconductor, as opposed to a metal supporting plasmons, light could not be concentrated to a mode volume smaller than
$(\lambda/2n)^{3}$
, where
$\lambda$
is the wavelength and
$n$
is the refractive index. This so-called «diffraction limit» was proven inapplicable by recent designs [1]–[3] and experimental results in silicon [4]. Here, we show that even in InP, with less mature nanofabrication technology, we can achieve deep sub-wavelength confinement of light, realizing a mode volume of
$0.26\times(\lambda/2n)^{3}$
.