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29 January 1985 Balanced Thermal Deflection Approach For Beam Handling In Medium Power Optical Systems
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Proceedings Volume 0518, Optical Systems Engineering IV; (1985) https://doi.org/10.1117/12.945192
Event: 1984 Cambridge Symposium, 1984, Cambridge, United States
Abstract
Optical systems including those applied in the areas of optical communication and optically assisted chemistry can involve energies of the order of 0.1 to 3 watts deposited in system optical elements. These energy levels are sufficient to induce significant bending of elements due to thermal gradients and to raise average elements temperature substantially. We have considered several forms of fused silica and ULE mirrors that control both the gradient induced bending and reduce the overall temperature rise. These mirror forms make use of high thermal conductivity materials bonded to the basic mirror and applications of conductively coupled heat sinks to reduce the effects of the thermal loads. We have found that a typical 2.5 cm diameter beam will result in surface deformations of less than 0.004 microns (peak) per deposited watt for steady-state conditions. For symmetric loading the majority of this deformation is found to be power. Finite element models of several mirror forms have been utilized to predict the detailed deflection distribution of the thermally loaded mirrors. Nastran predicted deflections were then decomposed into Zernike polynomial representations of the surface. By utilizing material choice as a degree of freedom in multi-element system design, we have found it possible to define beam handling systems that have very little thermally induced defocus for symmetric thermal loading. Heat rejection from the system utilizes controlled conduction to minimize structural deflections of the supporting structure. For asymmetric loading, higher order aberrations begin to appear and the control of thermally induced system wavefront error becomes more difficult. The major aberration, however, continues to be power for a significant range of beam decenter. Mounting geometry, thermal conductor configuration and bonding effects were included in the analysis. Good agreement between closed form and finite element analysis results was found for simplified check cases.
© (1985) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
T. L. Miller and R. D. Grigg "Balanced Thermal Deflection Approach For Beam Handling In Medium Power Optical Systems", Proc. SPIE 0518, Optical Systems Engineering IV, (29 January 1985); https://doi.org/10.1117/12.945192
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