Tsunami - Beckman Institute Laser Resource Center

Chapter 9
Maintenance
The condition of the laboratory environment and the amount of time you
use the laser affects your periodic maintenance schedule. The coated surfaces
of the elements forming the laser cavity-the output coupler, GTI or
high reflector, prisms, birefringent filter (ps version), mode locker, fold
and focus mirrors, and rod surfaces-most directly affect the performance
of the laser.
Do not allow smoking in the laboratory. Condensation due to excessive
humidity can also contaminate optical surfaces. The cleaner the environment,
the slower the rate of contamination.
If the laser head cover is left in place, there is little you must do day-today
to maintain the laser. To create a dust-free environment, allow purging,
and eliminate time-consuming maintenance, the Tsunami laser head
is sealed. All controls required for day-to-day operation are accessible
from the outside. The Model 3910 purge regulatorlfilter is provided as part
of the system to facilitate cavity purging. The clean, dry, nitrogen gas
keeps dust and moisture out of the laser head. Therefore, the laser head
cover should only be removed when absolutely necessary, e.g., when
changing its configuration from ps to fs and vice versa, or when changing
optic sets.
Although rarely required, you must change the filters in the Model 3910
purge unit from time to time when the desiccant in the sieve assembly
turns pink. Refer to the Model 3910 section at the end of this chapter.
When you finally do need to clean the optics, follow the procedures below.
Notes on the Cleaning of Laser Optics
Laser optics are made by vacuum-depositing microthin layers of materials
of varying indices of refraction onto glass or quartz substrates. If the surface
is scratched to a depth as shallow as 0.01 mm, the operating efficiency
of the optical coating can be reduced significantly and the coating can degrade.
Lasers are oscillators that operate with gain margins of a few percent. Losses
due to unclean intracavity optics, which might be negligible in ordinary
optical systems, can disable a laser. Dust on optical surfaces can cause loss
of output power, damage to the optics or total failure. Cleanliness is essential,
and you must apply laser optics maintenance techniques with extreme
care and with attention to detail.