Abstract

A membrane deformable mirror has been investigated for its potential use in high-energy laser systems. Experiments were performed in which the deformable mirror was heated with a 1kW incandescent lamp and the thermal profile, the wavefront aberrations, and the mechanical displacement of the membrane were measured. A finite element model was also developed. The wavefront characterization experiments showed that the wavefront degraded with heating. Above a temperature of 35°C, the wavefront characterization experiments indicated a dramatic increase in the high-order wavefront modes before the optical beam became immeasurable in the sensors. The mechanical displacement data of the membrane mirror showed that during heating, the membrane initially deflected towards the heat source and then deflected away from the heat source. Finite element analysis (FEA) predicted a similar displacement behavior as shown by the mechanical displacement data but over a shorter time scale and a larger magnitude. The mechanical displacement data also showed that the magnitude of membrane displacement increased with the experiments that involved higher temperatures. Above a temperature of 35°C, the displacement data showed that random deflections as a function of time developed and that the magnitude of these deflections increased with increased temperature. We concluded that convection, not captured in the FEA, likely played a dominant role in mirror deformation at temperatures above 35°C.

© 2008 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |

  1. Dassault Systems SIMULIA, Abaqus, http://www.simulia.com/

Other (1)

Dassault Systems SIMULIA, Abaqus, http://www.simulia.com/

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (7)

Fig. 1
Fig. 1

Photograph of the modified membrane mirror in a ceramic mount.

Fig. 2
Fig. 2

Optical layout used to measure the membrane surface properties through measurement of the wavefront aberration of a reflected optical beam. L 1 L 5 , imaging lenses; PBS, polarizing beam splitter. The dashed line indicates a low reflection optical enclosure.

Fig. 3
Fig. 3

Plot of the temperature as a function of the time for different radial positions on the membrane mirror. The temperature was measured using the S45 FLIR and the ThermCAM Researcher software.

Fig. 4
Fig. 4

Plot of the membrane displacement data at the center of the mirror as a function of time at different maximum membrane temperatures. The baseline is measured at room temperature ( 23 ° C ). The data were taken with the Fotonics Sensor. The temperature was measured using the S45 FLIR and the ThermCAM Reasearcher software.

Fig. 5
Fig. 5

Plot of the membrane displacement data at the edge of the mirror as a function of the time at different maximum membrane temperatures. The baseline is measured at room temperature ( 23 ° C ). The data were taken with the Fotonics Sensor. The temperature was measured using the S45 FLIR and the ThermCAM Reasearcher software

Fig. 6
Fig. 6

Plot of the finite element analysis data of the membrane displacement as a function of the time at the center of the mirror.

Fig. 7
Fig. 7

Time series plot demonstrating the effect of heating the membrane surface on the far-field beam quality after reflection. The original far-field beam profile is depicted on the left where the membrane is not heated. As the membrane is heated toward a threshold point the surface profile degrades the far-field Strehl, listed above in units of rms waves of aberration over all the modes. λ is 635 nm . The temperature was measured using the S45 FLIR and the ThermCAM Reasearcher software

Metrics