From Reinhard Schinke

From Reinhard Schinke

From Reinhard Schinke

From Reinhard Schinke

From Reinhard Schinke

Lasers: N2>>N1

B21W()

A13

2

1

3

B23Wp() A21 A23

Lasers: N2>>N1

B21W()

A13

fast

2

1

3

B23Wp() A21

slow

A23

Pump

Lase

Nd3+:Y3Al5O12 (YAG)

Cavity—2 mirrors separated by n/2

Lasers characterized by:DirectionalityMonochromaticBrightnessCoherence

Discuss: Threshhold

LinewidthsHomogeneous Broadening:

Affects every molecule the same way

e.g. time energy uncertainty principle and pressure broadening

h 1

sets a minimum linewidth of -1

Expressed as e-t/ decay of final state probability the corresponds after Fourier transform to a Lorentzian lineshape

22

0

2max

4/1

4/

IIL FWHM=

LinewidthsInhomogeneous broadening:

Collection of molecules have a distribution of transition energies. Typically given by statistics of different molecular environments and described by Gaussian functions.

220 2/

max eIIG FWHM=2(2ln2)

e.g. Doppler Broadening M

Tx

m

kT

C 71072ln

22

– Mon Feb 18 Presidents day

– Weds: Rayleigh and Raman Scattering

– Weds Feb 27: Projects Part1