Abstract

High-contrast imaging techniques such as coronagraphy are expected to play an important role in the imaging of extrasolar planets. Instruments like the Gemini Planet Imager (GPI) or the Spectro- Polar-Imetric High-Contrast Exoplanet Research (SPHERE) require high-dynamic range, achieved using coronagraphs to block light coming from the parent star. An extremely good adaptive optics (AO) system is required to reduce dynamic atmospheric wavefront errors to 50100nm  rms. Systematic wavefront errors must also be controlled at the nanometer-equivalent level to remove persistent speckle artifacts. While precision AO systems can control wavefront phase errors at this level, systematic amplitude or intensity errors can also produce speckle artifacts and are uncontrolled by traditional AO phase conjugation. On the Laboratory for Adaptive Optics (LAO) extreme AO testbed, we observed a discrepancy between the coronagraphic image profile and the profile predicted by simple simulations using the measured optical phase, which could potentially be explained by amplitude variations. Measurements showed up to 7%rms intensity changes across the microelectrical mechanical (MEM) plane of the system. We identified potential sources of amplitude variation and compared them to a Fresnel model of the system. One potential concern was the surface structure of the MEM system’s (MEMS) deformable mirror, but analysis shows that it induces at most 2%  rms variation. The bulk of the observed intensity variation is due to nonuniform illumination of the system by the input single-mode fiber and phase errors mixing into amplitude at the nonpupil-plane due to the Talbot effect, coupled with residual astigmatism in the pupil imager.

© 2009 Optical Society of America

Full Article  |  PDF Article
OSA Recommended Articles
The effect of a small heat source on PSF stability for high-contrast imaging

JuliaW. Evans, Bruce Macintosh, Andrew Norton, Daren Dillon, and Donald Gavel
Opt. Express 17(14) 11652-11664 (2009)

Demonstrating sub-nm closed loop MEMS flattening

Julia W. Evans, Bruce Macintosh, Lisa Poyneer, Katie Morzinski, Scott Severson, Daren Dillon, Donald Gavel, and Layra Reza
Opt. Express 14(12) 5558-5570 (2006)

Effect of wavefront error on 10−7 contrast measurements

Julia W. Evans, Gary Sommargren, Bruce A. Macintosh, Scott Severson, and Daren Dillon
Opt. Lett. 31(5) 565-567 (2006)

References

You do not have subscription access to this journal. Citation lists with outbound citation links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Cited By

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Figures (19)

You do not have subscription access to this journal. Figure files are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Metrics

You do not have subscription access to this journal. Article level metrics are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription