Ultrashort Laser Pulse Phenomena, 2nd Edition

Nonlinear Refractive Index Effects 411

Non-uniform heating results in convection, turbulence, and a random noise in

the beam profile and amplification. In the case of dye laser amplifiers, a simple

but effective solution consists of using aqueous dye solutions cooled near 4

◦

C,

because (dn/dT)|

4

◦

C

≈ 0 at that temperature (or 11. 7

◦

C for heavy water). Pulse-

to-pulse fluctuations in the output of a Cu vapor laser pumped amplifier have

been considerably reduced by this technique [20].

In the case of solid-state amplifiers, a careful design of a cylindrically sym-

metric pump (and cooling) geometry is required to prevent thermal lensing from

causing beam distortion. ...