Visible fibre lasers by downconversion

Cost-effective and efficient means of visible light creation, particularly RGB (Red, Green, Blue) generation, are crucial to the continuing success and growth of many data, video, and multi-media projector display technologies. Current projector light sources, although in widespread use around the world, leave much to be desired, as they tend to be both inefficient and not always reliable. Projector lamps suffer not just from relatively poor directionality in their optical emission, but also from its broad spectral content. For example, projector images are typically formed by the manipulation of the relative intensities of just 3 wavelength bands (RGB), with bandwidths of order 10 nm each. A broad white light spectrum thus has substantial portions of its energy discarded. The poor efficiencies of projector lamps also result in high heat dissipation, complicating projector design and compounding long term reliability issues. Current 'state-of-the-art' 200W ultra-high-pressure metal halide lamps are no more than 1% efficient, with specified - but not guaranteed - lifetimes of just 1,000 hours or so. Clearly, improved projector sources with the following desirable properties: a) high directionality in its optical emissionb) highly efficient, and emitting only within the required RGB wavelength bandsc) reasonably long lifetimes of > 10,000 hrs (an order of magnitude longer than current projector bulbs)could provide a considerable boost to a wide range of applicable display technologies. Direct diode-pumped visible fibre lasers are a potentially appealing candidate which could be capable of satisfying all of the above criteria.The next generation of DVD (Blu-Ray, HD-DVD) players will incorporate blue laser diodes operating at 405nm, which enable higher optical storage capacities by virtue of the shorter optical wavelength. The imminent widespread availability of these diode lasers - driven by the mass consumer electronics market - heralds the prospect of cheap blue laser pump sources which can, and surely will, be leveraged to advantage in a variety of other applications. It is in anticipation of this that we propose to investigate the impact on visible fibre laser technology, and the prospects for downconversion from blue diode lasers.