PALM
®
MicroBeam User Manual - 0202 Z
19
How to Prepare the PALM
®
MicroBeam for the Application
Laser energy and focus
6.4 Laser energy and focus
To be able to precisely cut the material and reliably
catapult it, the laser focus has to be set accurately/
properly to optimal values under various condi-
tions.
The diameter of the cuts is dependent on
- the numerical aperture of the objective used
- the position of the laser focus with regard to the
microscope focus
- the applied laser energy
- and on the absorption properties of the mate-
rial to be cut.
The ablation occurs within the area of the laser
focus (please see figure 14a). The smallest avail-
able cutting size can only be achieved within the
center of the laser focus using as little energy as
possible.
The catapulting is effected by a laser beam wid-
ened to the appropriate diameter with its focus
placed underneath the specimen to be catapulted
(please see figure 14b)
The laser beam is guided through the epifluo-
rescene channel of the microscope and is focused
with the objective of the microscope. Therefore the
energy and the size of the laser beam depend on
the kind of objective, which is used with the
device.
Generally the following is valid: The higher the
magnification, aperture and UV-Transmission of
the objective, the smaller the focus of the laser
and the higher the energy.
a
b
Figure 14
Position of the laser focus, when ablating or catapulting