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Titanium Sapphire Laser
Photon Physics 12 April 2006 Hendrik de Leeuw ( )
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TiSa in General Titanium Sapphire Laser = TiSa TiSa = Ti: Al2O3
Ti Al (0.1% in weight)
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Energy Tunable laser ( nm)
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Pumping
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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)
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Energy level scheme Boltzmann!
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Selection rules Laser ion : Ti3+ Neutral atom: 3d24s2
3d electron no excited state absorption Tunability is high
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Broadening mechanisms
Homogeneous broadening (T2 ) Electron- phonon interaction Vibronic transition (coupling electronic and vibrational states) Thus Lorentzian lineshape
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Specifics Gaincoefficient: 20 m-1
Stimulated emission cross-section: 3.4 * m2 Upper laser level lifetime = 3.2 s Saturation intensity Isat = hul /(ul u) = ( )* 109 W m-2
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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 %)
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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
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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
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Mode- locking Many TiSa lasers are Mode-locked Kerr mode-locking
Huge emission band Q-switching
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Mode- locking Many TiSa lasers are Mode-locked Kerr mode-locking
Huge emission band Q-switching But “large” cross-section!
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Recent experiment Molecular dyes (± 450 nm, freq doubled TiSa)
voltage dependent dyes, 5 ms Cells-vesicles Solvent relaxation
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Questions ?
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