Irradiation of lithium fluoride (LiF) crystals by low energy (few keV) electron beams gives rise to the efficient formation of stable laser active colour centres, mostly F2and F3+aggregate defects, on their surface. The presence of primary and aggregate point defects induces a local increase of the refractive index of the thin irradiated layer in the green-red spectral range, where the F3+and F2visible emissions are located. The use of electron-beam lithography techniques allows for the definition of coloured strips, so miniaturised optical active channel waveguides may be fabricated by a direct-writing process. We report on the observation of amplified spontaneous emission of the red light from LiF:F2centres in active waveguides realised with different irradiation doses in a LiF crystal, in order to determine the influence of this fundamental parameter on the amplification properties of these optical confining structures. Low pumping power densities have been used in quasi-continuous-wave regime at room temperature; the appreciable values of the gain coefficient, several cm-1, with an exciting power density of few hundreds mW/cm2, make this material a good candidate for the realisation of active integrated optical devices. © 2002 Elsevier Science Ltd. All rights reserved.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Physical and Theoretical Chemistry
- Electrical and Electronic Engineering