Enhancement of the photoluminescence of semiconductor nanocrystals in transfer-printed microcavities based on freestanding porous silicon photonic crystals

Today, lots of research address the phenomenon of interaction between light and matter. In particular, it is of a special interest to investigate light–matter interaction in one-dimensional resonators based on porous materials. In this case, one can embed emitting semiconductor particles into the porous resonator, where the excitons of these particles couple to the resonator eigenmode and luminescence intensity of the emitters is enhanced, allowing an increase in the sensitivity of optical sensors, detectors, and photonic diagnostic assays. A particular challenge is to place the emitters directly in the antinode region of the resonator eigenmode in order to maximize the coupling strength, which is sometimes a problem due to the spatial distribution of emitters away from the eigenmode localization region. Here, we have shown that the transfer-printing technique can be used to obtain structures based on freestanding porous silicon photonic crystals capable of precisely controlling the emitter spatial distribution about the eigenmode localization region. This, as well as the porosity of these structures and high adsorption capacity of porous silicon, allows the light–matter interaction in these hybrid structures to be used in sensing applications. We have shown that the transfer-printing method does not worsen the optical properties of the microcavities compared to the conventional electrochemical etching of the whole microcavity at a time. Furthermore, we have observed slightly better coupling of the exciton of the emitter to the eigenmode of the transfer-printed microcavity in the weak coupling regime.