Wednesday 8 December;Delft, Willem Vos "Photonic band gap crystals: Islands of tranquility in a fluctuating vacuum?"



Location: Zaal E
Time: 16:00 hrs


Control of spontaneous emission is a main manifestation of cavity quantum electrodynamics that is relevant to a broad range of applications such as efficient lasers and light emitting diodes, single-photon sources for quantum information, solar energy harvesting, and biological emitters. It is well known that the characteristics of spontaneously emitted light depend strongly on the environment of the light source. The effect of the environment on a source’s emission is described by the local density of optical states that counts the number of photon modes available for emission and that is interpreted as the density of vacuum fluctuations.

Currently, there are many efforts to control the emission of quantum emitters by optimizing the nanoscale environment using interfaces, microcavities, or antennae. A particularly interesting class of nanophotonic media are photonic band gap crystals. A photonic crystal has an intricate three-dimensional (3D) nanostructure with length scales on the order of the wavelength of light (see figure). To the eye photonic crystals have wonderful opalescent luster. The first ever control of spontaneous emission with photonic crystals was performed in Twente. In the regime of strong interaction between light and crystal a photonic band gap occurs. This gap is a frequency range where light is forbidden to exist by interference. Hence the density of vacuum fluctuations is radically inhibited. The emission rate will vanish, yet this has not been observed to date.

We will discuss silicon photonic bandgap crystals made with new CMOS-compatible nanofabrication methods, time-resolved spontaneous emission experiments, using quantum dots and molecules. We will briefly address ultrafast optical switching of photonic crystals and cavities, which is relevant to future photonic integrated circuits.