Lecture 8: Laser amplifiers

Neodymium-doped glass
Level 1 is 0.24 eV above the ground state. This is substantially
larger than the thermal energy 0.026 eV at room temperature, so
that the thermal population of the lower laser is negligible.
Level 3 is a collection of four absorption bands, centered at 805,
745, 585, and 520 nm.
The excited ions decay rapidly from level 3 to level 2 and then
remain in level 2 for a substantial time sp = 330 s. 1 is very
short (~ 300 ps)
The 2→1 transition is inhomogeneously broadened because of the
amorphous nature of the glass, which presents a different
environment at each ionic location. This material therefore has a
large spontaneous linewidth (gain bandwidth) ≈ 6 THz
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