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WP3 : Downscalling photonics

Friday 22 February 2013, by Alexandra Peereboom

There is a continuous push towards downscaling optical devices and optical systems, so as to reduce footprint and fabrication costs, while simultaneously obtaining increased reliability and stability. Here we will target two emerging application areas where downscaling may be extremely beneficial, namely optical sensing and quantum optics, and the devices needed to make them possible.

3.1 Microsources based on novel light emitting materials. One of the most critical parts in both applications is a downscaled source, generating the required light with ultra-low injection powers. Some very exciting devices were proposed and demonstrated in literature recently, using either photonic crystal cavities, metal confined cavities or semiconductor nanowires. All of these are based on a classical III-V platform however, and difficult to combine with the high index contrast silicon photonics platform, which is much more suited for further distribution of the generated signals (e.g. towards the sensing site or the quantum optics experiment integrated on the chip). Furthermore shifting to a new wavelength domain (e.g. MIR) requires a complete new material system. Therefore, in a first subtask we will develop sources that can overcome these problems. We will investigate new types of microsources compatible with high index contrast waveguide platforms in silicon and silicon nitride, targeting applications in miniaturized sensors, quantum information processing and communication. We will use novel types of luminescent materials including both quantum dots and organic molecules, in the visible, NIR and MIR.

3.2 Photonic sensing at the single molecule level. Optical sensors can offer a high sensitivity but are typically still very bulky and expensive, either because the sensor itself is large (e.g. because it requires a long interaction path length for inducing a measureable change in the signal), because the read-out system is large and not integrated (e.g. SERS) or because there is no efficient way to concentrate the analyte at the sensor site. These issues will be addressed in this second subtask. The different tracks include optical particle trapping using integrated waveguides, fully integrated sensors with new functional overlays for absorption and Raman spectroscopy and an advanced microfluidic system. Together these could form the ultimate miniaturized sensing platform.

3.3 Quantum optics and quantum information handling. Quantum optics experiments involving up to 6 photons have by now been realised by several groups. There is increasing interest in integrating quantum optics experiments on chips because of the required stability of the increasingly complex optical circuits involved, and because of the goal of combining quantum optics experiments with integrated single photon sources or solid-state memories for single photons. Different aspects of quantum optics with applications to quantum information will be investigated. These include quantum random number generators; novel, VCSEL based, squeezed light sources; and quantum optics experiments (such as entanglement generation and manipulation on the chip, Hong-Ou-Mandel dip, entanglement swapping) fully integrated on a silicon optics chip.

3.4 Increasing light-matter interaction. Several tracks enabling further downscaling will be investigated: slow light structures realised in the functionalized films developed in WP1; “liquid waveguides” formed by surface tension in a liquid deposited on a suitable patterned surface; improving the optical interfaces towards the integrated optical circuits used elsewhere in the project.