Continuous-wave amplification and light storage in optically and electrically pumped random laser media

Gain competition is analyzed theoretically on coupled stimulated emission transitions in -type configurations of excited atoms and compared with experimental observations in electrically and optically pumped random media. Under steady-state conditions, we predict and observe dramatic spectral quenching among F5/2 transitions in electron-beam-irradiated Nd3+: -Al2O3 nanopowders, identifying a simple mechanism that promotes laser action at the longest wavelength 405 nm . In optically pumped Nd:Y2O3 nanopowder, simultaneous laser action is observed at two previously unreported wavelengths of Nd3+ (763 and 821 nm), but spectral quenching is not observed, owing to the absence of coupling among the inverted transitions. Quantitative analysis of quenching and threshold behavior in the case of Nd3+: -Al2O3 indicates that in wavelength-sized volumes of these light-confining media the average storage time of light may be as long as 30 ps. © 2007 Optical Society of America OCIS codes: 140.5680, 140.3380, 140.3530.