Solution #1:
Static Thermal Compensation
With this method of thermal compensation we use a static configuration
of heating elements to radiatively heat the exterior of the optic and
"smooth out" the thermal gradients induced by the laser beam. We use
a simple ring of nichrome wire (wire that is commonly found in toasters),
coaxial to the laser beam.
While more compicated heater geometries can be tailored to correct arbitrary
axisymmetric wavefront distortions, a single ring should suffice to null a
LIGO II type thermal lens (click here for the
corrected optical path distortion (modeled) for a single heating ring
acting on the LIGO II input test mass).
The major drawback to the scheme of static thermal compensation is that it
is limited to static, axisymmetric wavefront distortions. Inhomogeneities in
bulk and surface absorption (perhaps accrued over time), as well as the
non-axisymmetric thermal lens generated at the beamsplitter cannot be dealt
with in this scheme. Thus, the next generation of the experiment (coming
in the spring of 2000) will be:
Solution #2: Dynamic Thermal Compensation
Last modified: Mon Nov 29 21:56:11 EST 1999