1. Titanium Sapphire Laser
Photon Physics
12 April 2006
Hendrik de Leeuw ( )

2. TiSa in General Titanium Sapphire Laser = TiSa TiSa = Ti: Al2O3
Ti Al (0.1% in weight)

3. Energy
Tunable laser ( nm)

4. Pumping

5. Pumping 2 Upper laser lifetime = 3.2 ms which is short So use:
Argon ion laser (cw operation)
Freq doubled
ND:YAG or
ND:YLF (pulsed operation)

6. Energy level scheme
Boltzmann!

7. Selection rules Laser ion : Ti3+ Neutral atom: 3d24s2
3d electron no excited state absorption
Tunability is high

8. Broadening mechanisms
Homogeneous broadening (T2 )
Electron- phonon interaction
Vibronic transition (coupling electronic and vibrational states)
Thus Lorentzian lineshape

9. Specifics Gaincoefficient: 20 m-1
Stimulated emission cross-section: 3.4 * m2
Upper laser level lifetime = 3.2 s
Saturation intensity Isat = hul /(ul u) = ( )* 109 W m-2

10. Specifics 2 topt = (g0 L a)1/2 -a = 21/2 a1/2 -a
With a absorption and scattering loss per pass and L =0.1 m.
The optimal transmission depends on output: pulsed (reflectivity %) cw (reflectivity 2-20 %)

11. Specifics 3 Output power: Back of the envelope:
up to 50W for cw
up to 1012 W for 100 fs pulses
Back of the envelope:
It= Isat/2 (g0L/(a+t)-1) t
Pt= It A
A 10 mm2 t= topt a  0, Pt =8 KW

12. Mode profile Single mode solid state laser: TEM00 (mode competition)
Number longitudinal modes:
 = c/2d = 1.5*108 s-1
FWHM= 1.0*1014 s-1
Nr_modes = FWHM/= 6.6 *104 modes

13. Mode- locking Many TiSa lasers are Mode-locked Kerr mode-locking
Huge emission band Q-switching

14. Mode- locking Many TiSa lasers are Mode-locked Kerr mode-locking
Huge emission band Q-switching But “large” cross-section!

15. Recent experiment Molecular dyes (± 450 nm, freq doubled TiSa)
voltage dependent dyes, 5 ms
Cells-vesicles
Solvent relaxation

16. Questions ?