EPSRC - Nanocluster Sensitised Optical Waveguide Amplifiers And Lasers

We propose to develop the technology for a new generation of optical waveguide amplifiers and lasers, focussing initially on the telecommunications area, but with broad applicability to optical systems which employ active optical sources. Current optical amplifiers are typically several metres of silica fibre doped with low concentrations of erbium ions, which luminesce at 1535nm - the wavelength region of choice for optical telecommunications. Such amplifiers require expensive pump lasers which comprise a major portion of the amplifier material costs. In addition, material limitations restrict their useful gain bandwidth to around 70nm. With growing demand for ever-higher data rates, data is being transmitted within closely spaced wavelength channels, potentially by as little as 0.1 nm. Increasingly narrow channel spacings require management of large numbers of wavelengths, with stringent demands on transmitter wavelength accuracy and stability. The result is burgeoning component, packaging and network management costs, posing a severe handicap to an industry attempting to drive both optical network capital and operating costs down. Clearly, a breakthrough in optical material design and fabrication that removes many of the constraints on the current optical gain medium could have a decisive impact on the industry.Our work will focus on semiconductor nanoclusters - 3-4 nm diameter clusters of silicon or germanium atoms that possess novel optical properties, including the ability to efficiently transfer optical excitation to nearby luminescent species. We aim to exploit the optical sensitisation effects of these nanoclusters, which allow us to couple optical energy into luminescent rare-earth, e.g. erbium, ions far more effectively than is possible in conventional rare earth-doped glasses. The broad absorption spectrum of the nanoclusters and their very large excitation cross-section will enable us to develop integrated planar optical devices that are pumped using cheap broad-band sources such as LEDs. Compared to the expensive lasers currently used, we stand to achieve a potential 100-fold reduction in pump power costs by deploying LEDs instead, opening the door for such devices to find applications in local area networks. Furthermore, we propose to co-dope the waveguides with more than one rare-earth ion in order to increase the amplifier gain bandwidth several-fold while maintaining a common pump sources.We propose to demonstrate two types of devices: waveguide amplifiers and lasers. Material will be produced at UCL using plasma enhanced chemical vapour deposition, and processed at UCL and Southampton to produce the devices.