| Abstract: |
Microlasers are usually composed of organic dyes that emit fluorescence with a high efficiency. Those dyes, however, lose their fluorescence function in a short time because of optically- or thermally-induced bleaching. This degradation is particularly serious with microdevices, since a high-powered beam is focused into a small volume of the device. The problem of the device degradation can be solved, if organic dyes are replaced by fluorescent lanthanide ions (europium, erbium, neodymium, etc.) that have a superior durability against optical and thermal hazards. The lanthanide ions, however, have a smaller absorption cross-section than organic dyes, and hence, a pump light for exciting the ions is absorbed insufficiently inside a microdevice. A long optical path is therefore required to enhance the excitation efficiency. Polyethylene glycol is a useful solvent for dispersing europium ions, since it turns to a translucent matrix by solidification. In this translucent matrix, pump light (396 nm wavelength) is scattered heavily, which leads to extension of the optical path and enhancement of the absorbance. Consequently, fluorescence of the europium ions (613 nm) becomes twofold stronger in the solid phase than the liquid phase. |