We demonstrate the feasibility of passive compensation of the thermal lens effect in fused silica optics, placing suitable optical materials with negative dn/dT in the beam path of a high power near IR fiber laser. Following a brief overview of the involved mechanisms, photo-thermal absorption measurements with a Hartmann-Shack sensor are described, from which coefficients for surface/coating and bulk absorption in various materials are determined. Based on comprehensive knowledge of the 2D wavefront deformations resulting from absorption, passive compensation of thermally induced aberrations in complex optical systems is possible, as illustrated for an F-Theta objective. By means of caustic measurements during high-power operation we are able to demonstrate a 60% reduction of the focal shift in F-Theta lenses through passive compensation.
An absorption measurement system was set up deploying a Hartmann-Shack wavefront sensor with extreme sensitivity
to accomplish spatially resolved monitoring of thermally induced wavefront distortions. Photothermal absorption
measurements in the near-infrared range were performed for both the characterization of optical materials and complete
F-Theta lenses, utilizing a 500 W Yb fiber laser (λ = 1070 nm) to induce thermal load.
Different combinations of bulk materials and AR coatings were examined to minimize absorption and to evaluate
potential approaches for thermal compensation. Additionally, bulk and surface / coating absorption coefficients were
determined by means of curve-fitting procedures. Furthermore, F-Theta lenses were tested to gain understanding of the
thermal behavior of the entire optical system.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.