Abstract

We describe a method of implementing a common-path phase-shifting point diffraction interferometric wavefront sensor suitable for extreme adaptive optics. The sensor simultaneously gives two phase-shifted outputs which can be used to drive a phase-only wavefront corrector. The device can also give a null output which can be used to calibrate any scintillation. Simulations are performed showing the utility of the device and experimental results of a high speed single channel closed loop system are presented.

© 2005 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |

  1. J. R. P. Angel. �??Ground-based imaging of extrasolar planes using adaptive optics,�?? Nature 368, 203-207, (1994)
    [CrossRef]
  2. K. L. Baker, E. A. Stappaerts, S. C. Wilks, P. E. Young, D. T. Gavel, J. W. Tucker, D. A. Silva and S. S. Olivier. �??Open- and closed-loop aberration correction by use of a quadrature interferometric wave-front sensor,�?? Opt. Lett. 29, 47-49 , 2004
    [CrossRef] [PubMed]
  3. K.L. Baker, E.A. Stappaerts, D. Gavel, S.C. Wilks, J. Tucker, D.A. Silva, J. Olsen, S.S. Olivier, P.E. Young, M.W. Kartz, L.M. Flath, P. Krulevitch, J. Crawford, O. Azucena. �??Breadboard testing of a phase-conjugate engine with an interferometric wave-front sensor and a microelectromechanical systems-based spatial light modulator,�?? Appl. Opt. 43, 5585-5593, (2004)
    [CrossRef] [PubMed]
  4. M. Langlois, R. Angel, M. Lloyd-Hart, F. Wildi, G.D. Love and A. Naumov. �??High Order Reconstructor Free Adaptive Optics for 6-8 metre class telescopes�?? Proceedings of the ESO Conference on Beyond Conventional Adaptive Optics, May 7-10, Venice (2001)
  5. E. E. Bloemhof and J. K. Wallace, �??Simple broadband implementation of a phase contrast wavefront sensor for adaptive optics,�?? Opt. Express 12, 6240-6245, (2004) <a href= "http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-25-6240">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-25-6240</a>
    [CrossRef] [PubMed]
  6. H. Kadono, M. Ogusu and S. Toyooka. �??Phase shifting common path interferometer using a liquid-crystal phase modulator,�?? Opt. Commun, 110, 391-400 (1994)
    [CrossRef]
  7. C. R. Mercer and K. Creath. �??Liquid crystal point diffraction interferometer for wave-front measurements,�?? Appl. Opt. 35, 1633-1642 (1996).
    [CrossRef] [PubMed]
  8. G.D. Love and R. Bhandari. �??Optical properties of a QHQ ferroelectric liquid crystal phase modulator,�?? Opt. Commun. 110, 475-478 (1994)
    [CrossRef]
  9. R. Bhandari and G. D Love. "Polarization eigenmodes of a QHQ retarder�??some new features,�??�?? Opt. Commun. 110, 479-484 (1994).
    [CrossRef]
  10. Meadowlark Optics, 5964 Iris Parkway, Frederick, CO 80530-1000, USA. Meadowlark Optics, 5964 Iris Parkway, Frederick, CO 80530-1000, USA. <a href= "http://www.meadowlark.com">http://www.meadowlark.com</a>
  11. G.D. Love, �??Wavefront correction and production of Zernike modes with a liquid crystal SLM.�?? Appl. Opt. 36, 1517-1524 (1997).
    [CrossRef] [PubMed]
  12. G.D. Love. �??Liquid crystal phase modulator for unpolarized light,�?? Appl. Opt. 32:2222-2223 (1993).
  13. S.R. Restaino, D. Dayton, S. Browne, J. Gonglewski, J. Baker, S. Rogers, S. McDermott, J. Gallegos and M. Shilko. �??On the use of dual frequency nematic material for adaptive optics systems: first results of a closed-loop experiment,�?? Opt. Express 6, 2-6 (1999) <a href= "http://www.opticsexpress.org/abstract.cfm?URI=OPEX-6-1-2">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-6-1-2</a>
    [CrossRef]
  14. V. A. Dorezyuk, A.F. Naumov, V.I. Shmal�??gauzen, �??Control of liquid crystal correctors in adaptive optical systems�??, Sov. Tech. Phys. 34, 1389-1392 (1989).
  15. A.K. Kirby & G.D. Love. �??Fast, large and controllable phase modulation using dual frequency liquid crystals,�?? Opt. Express 12, 1470-1475 (2004) <a href= "http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-7-1470">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-7-1470</a>
    [CrossRef] [PubMed]

Appl. Opt.

ESO Beyond Conventional Adapt. Opt. '01

M. Langlois, R. Angel, M. Lloyd-Hart, F. Wildi, G.D. Love and A. Naumov. �??High Order Reconstructor Free Adaptive Optics for 6-8 metre class telescopes�?? Proceedings of the ESO Conference on Beyond Conventional Adaptive Optics, May 7-10, Venice (2001)

Nature

J. R. P. Angel. �??Ground-based imaging of extrasolar planes using adaptive optics,�?? Nature 368, 203-207, (1994)
[CrossRef]

Opt. Commun.

G.D. Love and R. Bhandari. �??Optical properties of a QHQ ferroelectric liquid crystal phase modulator,�?? Opt. Commun. 110, 475-478 (1994)
[CrossRef]

R. Bhandari and G. D Love. "Polarization eigenmodes of a QHQ retarder�??some new features,�??�?? Opt. Commun. 110, 479-484 (1994).
[CrossRef]

H. Kadono, M. Ogusu and S. Toyooka. �??Phase shifting common path interferometer using a liquid-crystal phase modulator,�?? Opt. Commun, 110, 391-400 (1994)
[CrossRef]

Opt. Express

Opt. Lett.

Sov. Tech. Phys.

V. A. Dorezyuk, A.F. Naumov, V.I. Shmal�??gauzen, �??Control of liquid crystal correctors in adaptive optical systems�??, Sov. Tech. Phys. 34, 1389-1392 (1989).

Other

Meadowlark Optics, 5964 Iris Parkway, Frederick, CO 80530-1000, USA. Meadowlark Optics, 5964 Iris Parkway, Frederick, CO 80530-1000, USA. <a href= "http://www.meadowlark.com">http://www.meadowlark.com</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 (7)

Fig. 1.
Fig. 1.

Concept for a common path point diffraction interferometer based on a ferroelectric liquid crystal (FLC) phase shifter. The FLC is essentially a switchable half-wave plate placed between two quarter-wave plates (QWP). The devices works with unpolarized input light to give two simultaneous interferograms which are orthogonally polarized, phase shifted by half a wave, and which are then separated by a polarizing beamsplitter.

Fig. 2.
Fig. 2.

Simulation results of the residual rms wavefront error from measurements of aberrated wavefronts. The test wavefronts were pure Zernike modes, as indicated on the x-axis and the amplitude of the applied mode is shown on the y-axis. It can be seen that measurement quality decreases with increasing amplitude, as is expected.

Fig. 3.
Fig. 3.

Simulation results showing the effect of calibration for scintillation. The red line shows a scan through the residual phase error if no attempt is made to correct for scintillation. The phase was reconstructed using equation 1. The blue line shows the residual phase error when the phase was reconstructed using equation 2.

Fig. 4.
Fig. 4.

Diagram of the closed loop system. Unpolarized light from the laser passes through the turbulence generator, followed by the LC wavefront corrector. The wavefront sensor, formed by the two quarter-wave plates (QWPs) and the FLC half-wave plate (HWP) followed by the polarizing beamsplitter, produces 2 signals on the photodiodes. Pinholes before the photodiodes ensure that the correct pixel on the wavefront corrector is being imaged onto the detectors. The differential signal from the photodiodes (which is the wavefront sensor output) is then compared with a reference DC signal in a comparator, which is used to control an analogue switch which supplies the wavefront corrector with a high voltage low or high frequency voltage.

Fig. 5.
Fig. 5.

Wavefront sensor output, measured after the differential amplifier (in fig. 4.), with the loop not closed, and an alternating signal of 1 wave being applied to the wavefront corrector.

Fig. 6.
Fig. 6.

Calibrated wavefront sensor output without (left) and with (right) the loop closed. The turbulence was severe (from a hot air blower). The uncorrected and corrected phase variances are 2.44 rad2 0.40 rad2 respectively.

Fig. 7.
Fig. 7.

Power spectrum of the wavefront sensor output with the loop not closed (red line) and closed (blue line). The system is reducing wavefront aberrations up to a crossover frequency of about 700Hz.

Tables (1)

Tables Icon

Table 1. Simulated residual wavefront errors showing that errors can be reduced by accounting for the scintillation by also measuring the pupil intensity. In the system described here this can be done without non-common path errors by recording data when the FLC is off.

Equations (4)

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

I A , B = I 0 [ 1 + γ cos ( ϕ ( x , y ) ϕ ¯ ± π 2 ) ] ,
I A , B = I 0 [ 1 γ sin ( φ ( x , y ) φ ¯ ) ] ,
sin φ m = 1 γ [ I B I A I B + I A ] .
ϕ m = I B I A I B + I A .

Metrics