William Angerer - Department of Physics and Astronomy - University ...

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measurements. Typically, I increased (decreased) the BP2 monochrometer setting by
",2 mm for every 40 nm decrease (increase) in the wavelength of the laser.
3.3.1 Techniques for Optimizing the Performance of the Ti:Ah03 Laser
vVe conclude this section by listing some techniques for alignment of the Ti:Al 2 0 3
laser. Aligning the Ti:Al 2 0 3 laser to lase is fairly easy, but aligning the Ti:Al 2 0 3 to
modelock and produce femtosecond pulse over a wide frequency range is somewhat
difficult. The mode quality of the Argon pump laser is critical for optimal operation
of the Ti:Ab03' The transverse mode of the Argon laser must be Gaussian. Higher
order spatial modes, e.g. TEMOl and TEMIO, may be eliminated from the Argon beam
by reducing the aperture setting of the laser. The smaller diameter of the aperture
attenuates the higher order modes more than the Gaussian modes, and hence reduces
the higher order modes relative to the Gaussian mode. (~ormally the aperture is set
to 8, but I have occasionally pumped the Ti:Ah03 with an aperture setting of 6 or 7).
Another common problem with the Argon laser is contamination of the Brewster
window. The Brewster window is a quartz window that seals the Argon laser tube.
The normal to the window is 45° from vertical. This window frequently picks up dust.
which is almost immediately burned onto the window. The power and mode quality
of the Argon laser diminishes significantly once the window has been contaminated.
The contaminant may be observed by inspecting the Brewster window during laser
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