Efficient visible (i.e. Red, Green and Blue) laser emissions are desirable for many applications such as optical data storage, reprographics, RGB colour displays, submarine communications, spectroscopy and biotechnology. These applications would benefit from an inexpensive, low noise, good beam quality and highly stable laser source. There are many different methods in which to achieve a visible laser source, these include nonlinear frequency conversion of high powered lasers, the relatively new process of upconversion and semiconductor lasers using a choice of materials for the blue/green spectrum.
By using standard microfabrication techniques, we propose to fabricate compact, mass-producible, high power, high efficiency visible wavelength lasers based on an upconversion process. An upconversion laser operates on the same principle as ordinary lasers. However, the difference comes with the pumping process. The energy from two or more pump photons is combined to excite the already excited atom to a much higher laser level leading to a shorter lasing wavelength than the pump wavelength when it relaxes to the lower energy level.
However, upconversion lasers require a host with a low phonon energy, otherwise multi-phonon transitions reduce the lifetime of the metastable levels making lasing impossible. Therefore, the objectives of our research are:
â¢ To identify a suitable low phonon host, â¢ Co-dope the host with rare-earth ions: Erbium and Ytterbium, â¢ Fabricate a low loss planar ridge waveguide using the co-doped host material and produce an efficient green laser source.
Once successful, we will further our research using different rare earths to achieve a range of visible laser sources.