Rare earth doped gain media

Rare earth ions doped in the dielectric materials seem to be ideal quantum-dots with much smaller size than those of artificial quantum dots made of semi-conductors. Therefore, rare earth trivalents can act as eminently effective luminous ions in laser gain media.

The advantage of the rare-earth trivalent as a luminous ion

Narrow emission bandwidth

Narrow bandwidth is due to the small interaction with other electrons in dofferent energy level/ the crystal field/ lattice vibrations. This narrow bandwidth enables stored energy inside laser gain media to be effectively connected to the laser output.

Long lifetime of the excited state

Since the dipole transition between laser upper and lower level is parity forbidden, the lifetime of excited states in rare-earth trivalent is 1,000 - 1,000,000 times longer than other luminous materials.

Large radiative quantum efficiency

Dielectric shielding by 5s/5p octet around HOMO consisted by 4f-electrons suppresses the quenching and diffusion processes caused by the interaction to other rare-earth trivalent. As a result of this suppression, the energy leakage from laser gain media become weakened.

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