Abstract

We present here new experimental results on high contrast imaging of 10-7 at 4.5λ/D (λ=0.820 microns) by combining a circular focal plane mask (coronagraph) of 2.5λ/D diameter and a multi-Gaussian pupil plane mask. Both the masks were fabricated on very high surface quality (λ/30) BK7 optical substrates using nano-fabrication techniques of photolithography and metal lift-off. This process ensured that the shaped masks have a useable edge roughness better than λ/4 (rms error better than 0.2 microns), a specification that is necessary to realize the predicted theoretical limits of any mask design. Though a theoretical model predicts a contrast level of 10-12, the background noise of the observed images was speckle dominated which reduced the contrast level to 4×10-7 at 4.5λ/D. The optical setup was built on the University of Illinois Seeing Improvement System (UnISIS) optics table which is at the Coude focus of the 2.5-m telescope of the Mt. Wilson Observatory. We used a 0.820 micron laser source coupled with a 5 micron single-mode fiber to simulate an artificial star on the optical test bench of UnISIS.

© 2005 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |

  1. Debes, John H.; Ge, Jian; Chakraborty, Abhijit, �??First High-Contrast Imaging Using a Gaussian Aperture Pupil Mask,�?? Astrophys. J. Lett. 572L, 165-168, (2002)
    [CrossRef]
  2. Debes, John H.; Ge, Jian; Kuchner, Marc J.; Rogosky, Michael �??Using Notch-Filter Masks for High- Contrast Imaging of Extrasolar Planets,�?? Astrophys. J. 608, 1095-1099, (2004)
    [CrossRef]
  3. Wilhelmsen Evans, Julia; Sommargren, Gary; Poyneer, Lisa; Macintosh, Bruce A.; Severson, Scott; Dillon, Daren; Sheinis, Andrew I.; Palmer, Dave; Kasdin, N. Jeremy; Olivier, Scot, �??Extreme adaptive optics testbed: results and future work,�?? Proc. SPIE 5490, 954-959, (2004)
    [CrossRef]
  4. Kasdin, N. Jeremy; Vanderbei, Robert J.; Spergel, David N.; Littman, Michael G., �??Extrasolar Planet Finding via Optimal Apodized-Pupil and Shaped-Pupil Coronagraphs,�?? Astrophys. J. 582, 1147-1161, (2003)
    [CrossRef]
  5. Vanderbei, Robert J.; Kasdin, N. Jeremy; Spergel, David N., �??Checkerboard-Mask Coronagraphs for High-Contrast Imaging,�?? Astrophys. J. 615, 555-561, (2004)
    [CrossRef]
  6. Kuchner, Marc J.; Spergel, David N., �??Notch-Filter Masks: Practical Image Masks for Planet-finding Coronagraphs, �?? Astrophys. J. 594, 617-626, (2003)
    [CrossRef]
  7. Kuchner, M.J. , �??A Unified View of Coronagraph Image Masks,�?? preprint no. astro-ph/0401256 at htp://xxx.lanl.gov/archive/astro, (2004) <a href=" htp://xxx.lanl.gov/archive/astro, (2004)">htp://xxx.lanl.gov/archive/astro, (2004)</a>.
  8. Debes, John H.; Ge, Jian, �??High-Contrast Imaging with Gaussian Aperture Pupil Masks,�?? PASP, 116, 674-681, (2004)
    [CrossRef]
  9. Nakajima, T.; Oppenheimer, B. R.; Kulkarni, S. R.; Golimowski, D. A.; Matthews, K.; Durrance, S. T., �??Discovery of a Cool Brown Dwarf,�?? Nature 378, 463-464, (1995)
    [CrossRef]
  10. Oppenheimer, Ben R.; Sivaramakrishnan, A.; Makidon, R.B., �??Imaging Exoplanets: The role of small Telescopes,�?? in The Future of Small Telescopes in the New Millennium, T. Oswalt, ed., III, (Dordrecht: Kluwar), p.157-174, (2003)
  11. Oppenheimer, Ben R.; Digby, Andrew P.; Newburgh, Laura; Brenner, Douglas; Shara, Michael; Mey, Jacob; Mandeville, Charles; Makidon, Russell B.; Sivaramakrishnan, Anand; Soummer, Remi; and 7 coauthors, �??The Lyot project: toward exoplanet imaging and spectroscopy,�?? Proc. SPIE 5490, 433-442, (2004)
    [CrossRef]
  12. Spergel, D.N., �??A New Pupil for Detecting Extrasolar Planets,�?? preprint no. astro-ph/0101142 at http://xxx.lanl.gov/archive/astro, (2001) <a href= "http://xxx.lanl.gov/archive/astro, (2001)">http://xxx.lanl.gov/archive/astro, (2001)</a>.
  13. Kuchner, Marc J.; Traub, Wesley A., �??A Coronagraph with a Band-limited Mask for Finding Terrestrial Planets,�?? Astrophys. J. 570, 900-908, (2002)
    [CrossRef]
  14. Sivaramakrishnan, Anand; Lloyd, James P.; Hodge, Philip E.; Macintosh, Bruce A., �??Speckle Decorrelation and Dynamic Range in Speckle Noise-limited Imaging,�?? Astrophys. J. Lett. 581, 59-62, (2002)
    [CrossRef]
  15. Thompson, Laird A.; Xiong, Yao-Heng, �??Laser beacon system for the UnISIS adaptive optics system at the Mount Wilson 2.5-m telescope,�?? Proc. SPIE 2534, 38-47, (1995)
    [CrossRef]
  16. Thompson, Laird A.; Castle, Richard M.; Teare, Scott W.; McCullough, Peter R.; Crawford, Samuel L., �??UnISIS: a laser-guided adaptive optics system for the Mt. Wilson 2.5-m telescope,�?? Proc. SPIE 3353, 282-289, (1998)
    [CrossRef]
  17. Thompson, Laird A.; Teare, Scott W., �??Rayleigh Laser Guide Star Systems: Application to the University of Illinois Seeing Improvement System,�?? PASP 114, 1029-1042, (2002)
    [CrossRef]
  18. Thompson, Laird A.; Teare, Scott W.; Crawford, Samuel L.; Leach, Robert W., �??Rayleigh Laser Guide Star Systems: UnISIS Bow-Tie Shutter and CCD39 Wavefront Camera,�?? PASP 114, 1143-1149, (2002)
    [CrossRef]
  19. Thompson, Laird A.; Teare, Scott W.; Xiong, Yao-Heng; Chakraborty, Abhijit; Gruendl, Robert, �??Progress with UnISIS: a Rayleigh laser-guided adaptive optics system,�?? Proc. SPIE 5490, 90-96, (2004)
    [CrossRef]
  20. Handbook of Microlithography, Micromachining and Microfabrication Vol. 1, Rai-Choudhury, P., editor SPIE Optical Engineering Press ; London, UK : Institution of Electrical Engineers, (1997)
  21. Sivaramakrishnan, Anand; Koresko, Christopher D.; Makidon, Russell B.; Berkefeld, Thomas Kuchner, Marc J., �??Ground-based Coronagraphy with High-order Adaptive Optics,�?? Astrophys. J. 552 397-408, (2001)
    [CrossRef]
  22. Trauger, John; Burrows, Chris; Gordon, Brian; Green, Joseph; Lowman, Andrew; Moody, Dwight; Niessner, Albert; Shi, Fang; Wilson, Daniel, �??Coronagraph contrast demonstrations with the High Contrast Imaging Testbed,�?? Proc. SPIE 5487, 1330-1336, (2004)
    [CrossRef]

Astrophys. J. (6)

Kasdin, N. Jeremy; Vanderbei, Robert J.; Spergel, David N.; Littman, Michael G., �??Extrasolar Planet Finding via Optimal Apodized-Pupil and Shaped-Pupil Coronagraphs,�?? Astrophys. J. 582, 1147-1161, (2003)
[CrossRef]

Vanderbei, Robert J.; Kasdin, N. Jeremy; Spergel, David N., �??Checkerboard-Mask Coronagraphs for High-Contrast Imaging,�?? Astrophys. J. 615, 555-561, (2004)
[CrossRef]

Kuchner, Marc J.; Spergel, David N., �??Notch-Filter Masks: Practical Image Masks for Planet-finding Coronagraphs, �?? Astrophys. J. 594, 617-626, (2003)
[CrossRef]

Debes, John H.; Ge, Jian; Kuchner, Marc J.; Rogosky, Michael �??Using Notch-Filter Masks for High- Contrast Imaging of Extrasolar Planets,�?? Astrophys. J. 608, 1095-1099, (2004)
[CrossRef]

Kuchner, Marc J.; Traub, Wesley A., �??A Coronagraph with a Band-limited Mask for Finding Terrestrial Planets,�?? Astrophys. J. 570, 900-908, (2002)
[CrossRef]

Sivaramakrishnan, Anand; Koresko, Christopher D.; Makidon, Russell B.; Berkefeld, Thomas Kuchner, Marc J., �??Ground-based Coronagraphy with High-order Adaptive Optics,�?? Astrophys. J. 552 397-408, (2001)
[CrossRef]

Astrophys. J. Lett. (2)

Sivaramakrishnan, Anand; Lloyd, James P.; Hodge, Philip E.; Macintosh, Bruce A., �??Speckle Decorrelation and Dynamic Range in Speckle Noise-limited Imaging,�?? Astrophys. J. Lett. 581, 59-62, (2002)
[CrossRef]

Debes, John H.; Ge, Jian; Chakraborty, Abhijit, �??First High-Contrast Imaging Using a Gaussian Aperture Pupil Mask,�?? Astrophys. J. Lett. 572L, 165-168, (2002)
[CrossRef]

Nature (1)

Nakajima, T.; Oppenheimer, B. R.; Kulkarni, S. R.; Golimowski, D. A.; Matthews, K.; Durrance, S. T., �??Discovery of a Cool Brown Dwarf,�?? Nature 378, 463-464, (1995)
[CrossRef]

New Millennium (1)

Oppenheimer, Ben R.; Sivaramakrishnan, A.; Makidon, R.B., �??Imaging Exoplanets: The role of small Telescopes,�?? in The Future of Small Telescopes in the New Millennium, T. Oswalt, ed., III, (Dordrecht: Kluwar), p.157-174, (2003)

PASP (3)

Debes, John H.; Ge, Jian, �??High-Contrast Imaging with Gaussian Aperture Pupil Masks,�?? PASP, 116, 674-681, (2004)
[CrossRef]

Thompson, Laird A.; Teare, Scott W., �??Rayleigh Laser Guide Star Systems: Application to the University of Illinois Seeing Improvement System,�?? PASP 114, 1029-1042, (2002)
[CrossRef]

Thompson, Laird A.; Teare, Scott W.; Crawford, Samuel L.; Leach, Robert W., �??Rayleigh Laser Guide Star Systems: UnISIS Bow-Tie Shutter and CCD39 Wavefront Camera,�?? PASP 114, 1143-1149, (2002)
[CrossRef]

Proc. SPIE (6)

Thompson, Laird A.; Teare, Scott W.; Xiong, Yao-Heng; Chakraborty, Abhijit; Gruendl, Robert, �??Progress with UnISIS: a Rayleigh laser-guided adaptive optics system,�?? Proc. SPIE 5490, 90-96, (2004)
[CrossRef]

Trauger, John; Burrows, Chris; Gordon, Brian; Green, Joseph; Lowman, Andrew; Moody, Dwight; Niessner, Albert; Shi, Fang; Wilson, Daniel, �??Coronagraph contrast demonstrations with the High Contrast Imaging Testbed,�?? Proc. SPIE 5487, 1330-1336, (2004)
[CrossRef]

Wilhelmsen Evans, Julia; Sommargren, Gary; Poyneer, Lisa; Macintosh, Bruce A.; Severson, Scott; Dillon, Daren; Sheinis, Andrew I.; Palmer, Dave; Kasdin, N. Jeremy; Olivier, Scot, �??Extreme adaptive optics testbed: results and future work,�?? Proc. SPIE 5490, 954-959, (2004)
[CrossRef]

Oppenheimer, Ben R.; Digby, Andrew P.; Newburgh, Laura; Brenner, Douglas; Shara, Michael; Mey, Jacob; Mandeville, Charles; Makidon, Russell B.; Sivaramakrishnan, Anand; Soummer, Remi; and 7 coauthors, �??The Lyot project: toward exoplanet imaging and spectroscopy,�?? Proc. SPIE 5490, 433-442, (2004)
[CrossRef]

Thompson, Laird A.; Xiong, Yao-Heng, �??Laser beacon system for the UnISIS adaptive optics system at the Mount Wilson 2.5-m telescope,�?? Proc. SPIE 2534, 38-47, (1995)
[CrossRef]

Thompson, Laird A.; Castle, Richard M.; Teare, Scott W.; McCullough, Peter R.; Crawford, Samuel L., �??UnISIS: a laser-guided adaptive optics system for the Mt. Wilson 2.5-m telescope,�?? Proc. SPIE 3353, 282-289, (1998)
[CrossRef]

SPIE Optical Engineering Press (1)

Handbook of Microlithography, Micromachining and Microfabrication Vol. 1, Rai-Choudhury, P., editor SPIE Optical Engineering Press ; London, UK : Institution of Electrical Engineers, (1997)

Other (2)

Spergel, D.N., �??A New Pupil for Detecting Extrasolar Planets,�?? preprint no. astro-ph/0101142 at http://xxx.lanl.gov/archive/astro, (2001) <a href= "http://xxx.lanl.gov/archive/astro, (2001)">http://xxx.lanl.gov/archive/astro, (2001)</a>.

Kuchner, M.J. , �??A Unified View of Coronagraph Image Masks,�?? preprint no. astro-ph/0401256 at htp://xxx.lanl.gov/archive/astro, (2004) <a href=" htp://xxx.lanl.gov/archive/astro, (2004)">htp://xxx.lanl.gov/archive/astro, (2004)</a>.

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 (6)

Fig. 1.
Fig. 1.

(a). The design of the Gaussian mask. 1b). Enlarged high resolution image (taken at the nano-fab facility) of the encircled defective region in Fig. 1a showing the smoothness of the edges (note the scale of 20 microns; rms error on the edges was measured to be about 0.2microns) as well as pin-hole defects and residual metal at the Gaussian edge. Such defects were not present in the second sample which was used for the experiment.

Fig. 2.
Fig. 2.

(a) (left): Photograph showing the GSPM replicated on a 25 mm diameter BK7 substrate mounted in its holder. (b) (right): Sketch of the basic optical train of the test-bed set up shown in Fig. 3. Some of the elements that were not used (flipped) for recording the coronagraphic images are eliminated in this sketch, like the Pupil Re-Imaging Lens, the Dichroic Beam Splitter, Flip Mirror (M2), and the video camera (located on kinematic mounts between the Imaging Lens L3 and the CCD).

Fig. 3.
Fig. 3.

Optical setup of the test-bench on the UnISIS AO optics table. Legend: Smf=Single mode fiber artificial star L1=Imaging Lens for image plane I1, I1=1st Image plane (for test-bench Coronagraph; focal plane mask), M1=Flip Mirror (for bending the beam), L2=Collimator Lens, GSPM=Gaussian Shaped Pupil Mask, L3=Final Imaging Lens onto the detector, DC=Dichroic Beam Splitter (50–50 between optical/NIR), M2=Flip Mirror 2, for redirecting the beam onto a video camera (VC) solely used for optical alignment purposes.

Fig. 4.
Fig. 4.

(a) (left) Laser 0.82 micron point source log stretched negative image showing the Airy pattern before introducing the focal plane mask (coronagraph) at the focal plane and GSPM at the pupil plane. (b) (right) a positive log stretched image of the uniformly illuminated GSPM (see text for details). The pupil reimaging lens has a wider field of view than the f/81 principal beam of the optical train. The intensity variations seen within the GSPM are probably due to light scattering and multiple reflections from the two surfaces of the BK7 substrate as well as light scattered at larger angles as seen by the pupil re-imaging lens.

Fig. 5.
Fig. 5.

(a) (left) Theoretically simulated model PSF with 2.5λ/D focal plane mask and the GSPM (negative image). (b) (right) The observed PSF (log stretched negative image) on the UnISIS optics table using 0.82 micron laser source coupled with a 5 micron single mode fiber as an artificial star. Note that the high contrast region is along the “red” line in the images. The observed PSF is the median of nine 10s images (in (b)). The image shows many speckles (tiny back dots) in the high contrast region making the background speckle-noise limited rather than detector-noise limited. See text for details.

Fig. 6.
Fig. 6.

A comparison of line profiles showing normalized contrast levels of observed and model PSF across the “red” line in the high contrast region (see Figs. 5(a) and 5(b). The difference between the two is mainly due to speckle noise in the observed PSF line profile. The y-axis represents the normalized dynamic range or the contrast level (normalized with respect to the peak intensity of the un-obscured test star with the GSPM at the Lyot plane). The two bold solid lines at ±1.25λ/D show the width of the 2.5λ/D focal plane mask. Also, between ±2λ/D the observed line profile is saturated due to spill-over of scattered light over the edges of the focal plane mask.

Equations (2)

Equations on this page are rendered with MathJax. Learn more.

y t = a R { exp [ ( α x R ) 2 ] exp ( α 2 ) } , and y b = b R { exp [ ( α x R ) 2 ] exp ( α 2 ) }
L d = D ( F ) * 2 D s

Metrics