Microscale Testing and Characterization Techniques for Benchmarking Crystal. . .
105
Fig. 5 Image of three-axis
stage system and laser
machining optics
script in the stage controller software. The laser beam remains focused in the same
spot during machining and the sample is moved to trace out the desired shape rather
than having the beam move on the sample to perform the machining. The reason for
this is that the beam will cut the same way every time since it is stationary, resulting
in a consistent machining procedure.
As with any laser system, safety is an important consideration, but especially
so in this case because the 780 nm wavelength of the laser beam is invisible to
the human eye. Laser safety eyewear must be worn at all times, the laser safety
containment box must remain closed during laser machining and a set of safety
interlocks installed on the doors to the lab. These interlocks will trip and close the
laser shutter if the doors are opened.
As with the other microtensile machining tools described in this chapter, there
are many special techniques that can be used with femtosecond laser machining
to improve sample quality. Once the spot size of the beam has been properly
minimized by adjusting the focal plane, the main parameters that can be changed
in the laser machining setup are the energy of the laser and the speed at which
the stage moves. The laser energy is a critical aspect to material removal because
the ablation threshold must be reached for vaporization of each material [80–83].
Increasing the energy of the beam will result in a higher rate of material removal and
a larger effective spot size, because more of the beam at the edges of its Gaussian
profile will be above the ablation threshold. However, increasing the energy will
also impose more damage in the sample. Care must be taken to select a correct
105
Fig. 5 Image of three-axis
stage system and laser
machining optics
script in the stage controller software. The laser beam remains focused in the same
spot during machining and the sample is moved to trace out the desired shape rather
than having the beam move on the sample to perform the machining. The reason for
this is that the beam will cut the same way every time since it is stationary, resulting
in a consistent machining procedure.
As with any laser system, safety is an important consideration, but especially
so in this case because the 780 nm wavelength of the laser beam is invisible to
the human eye. Laser safety eyewear must be worn at all times, the laser safety
containment box must remain closed during laser machining and a set of safety
interlocks installed on the doors to the lab. These interlocks will trip and close the
laser shutter if the doors are opened.
As with the other microtensile machining tools described in this chapter, there
are many special techniques that can be used with femtosecond laser machining
to improve sample quality. Once the spot size of the beam has been properly
minimized by adjusting the focal plane, the main parameters that can be changed
in the laser machining setup are the energy of the laser and the speed at which
the stage moves. The laser energy is a critical aspect to material removal because
the ablation threshold must be reached for vaporization of each material [80–83].
Increasing the energy of the beam will result in a higher rate of material removal and
a larger effective spot size, because more of the beam at the edges of its Gaussian
profile will be above the ablation threshold. However, increasing the energy will
also impose more damage in the sample. Care must be taken to select a correct