Spectral line in a discrete spectrum as images of the entrance slit of a spectrograph

Discrete and continuous absorption spectra for atoms (a) and molecules (b)

Prominent Fraunhofer absorption lines within the visible and near UV spectral range

Continuous “bound-free” and discrete “bound-bound” flurescence transitions of the NaK molecule observed upon laser excitation at l=488 nm. (a) Spectrum (b) enlargement(vibration bands) (c) level scheme

E Ek E2 E1 E0 Recombination continuum collision induced transitions fluorescent lines collision induced transitions Recombination continuum E0 E l IFL Discrete and continuous emission spectrum and the corresponding level diagram.

LASER RESONATORS Perfectly parallel Misalignment : escapes

A laser resonator with mirrors that are spherical surfaces

q r(z) z A ray is characterized by its displacement r and slope r’.

Stability condition

plane-parallel resonator spherical resonator(concentric) hemispherical resonator

confocal resonator hemiconfocal resonator

Semiclassical description : absorbtion Ea Eb

Perturbation theory Eigen function of the unperturbed atom

dipole matrix element

Weak field approximation