Abstract

Boundary-layer turbulence resulting from uneven airflow around window interfaces can impact airborne laser communications (lasercom). In the focal plane, these distortions can produce fast jitter and beam break-up, posing challenges for tracking and communications. We demonstrate an experimental emulator that reproduces aircraft aero-optical distortions using a deformable mirror. This boundary-layer emulator resides in a hardware testbed that experimentally mimics air-to-space lasercom links in a controlled, laboratory environment. The boundary-layer emulator operates in the 1.55-μm band and accurately recreates aero-optical distortions at a rate of 2 kilo-frames per second.

© 2009 Optical Society of America

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References

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  1. S. G. Lambert and W. L. Casey, Laser Communications in Space (Artech House, Norwood, MA, 1995), Chap. 3.
  2. R. Parenti, R. J. Sasiela, L. C. Andrews, and R. L. Phillips, "Modeling the PDF for the irradiance of an uplink beam in the presence of beam wander," Proc. SPIE 6215, 621508.1-13 (2006).
  3. T. G. Bifano, J. A. Perreault, and P. A. Bierden "A micromachined deformable mirror for optical wavefront compensation," Proc. SPIE 4124, 7-14 (2000).
    [CrossRef]
  4. J. M. Roth, R. J. Murphy, W. E. Wilcox, and R. A. Conrad, "Experimental Emulation of Air-to-Space Laser Communication Links," 2008 IEEE-LEOS Annual Meeting, 13 November 2008, Paper ThAA2, 886-7.
  5. R. A. Conrad, R. J. Murphy, T. H. Williams, W. E. Wilcox, S. Michael, and J. M. Roth, "Experimental comparison of tracking algorithms in the presence of aircraft boundary-layer distortions for emulated free-space laser communication links," Appl. Opt. 48, A98-A106 (2009).
    [CrossRef]
  6. J. M. Roth, R. E. Bland, and S. I. Libby, "Large-Aperture Wide Field of View Optical Circulators," IEEE Photon. Technol. Lett. 17, 2128-2130 (2005).
    [CrossRef]
  7. Y. Zhou and T. Bifano, "Characterization of Contour Shapes Achievable with a MEMS Deformable Mirror," Proc. SPIE 6113, 123-130 (2006).
  8. Y. Zhou and T. Bifano, "Adaptive optics using a MEMS deformable mirror," Proc. SPIE 6018, 350-356 (2005).
  9. J. Wyant, "Zernike Polynomials," http://www.optics.arizona.edu/jcwyant/Zernikes/ZernikeP lynomialsForTheWeb.pdf
  10. R. A. Conrad, Impact of the Boundary Layer on Pointing and Tracking in Airborne Free-Space Laser Communication Links (Master’s Dissertation, Aeronautics & Astronautics Department, M.I.T., June 2008).
    [PubMed]
  11. S. Zheng, Tracking Algorithms Under Boundary Layer Effects for Free-Space Optical Communications (Master’s Dissertation, Department of Electrical Engineering & Computer Science, M.I.T., August 2007).
  12. T. Bifano, P. Bierden, and J. Perreault, "Micromachined Deformable Mirrors for Dynamic Wavefront Control," Proc. SPIE 5553, 1-16 (2004).
    [CrossRef]

2009 (1)

2006 (1)

Y. Zhou and T. Bifano, "Characterization of Contour Shapes Achievable with a MEMS Deformable Mirror," Proc. SPIE 6113, 123-130 (2006).

2005 (2)

Y. Zhou and T. Bifano, "Adaptive optics using a MEMS deformable mirror," Proc. SPIE 6018, 350-356 (2005).

J. M. Roth, R. E. Bland, and S. I. Libby, "Large-Aperture Wide Field of View Optical Circulators," IEEE Photon. Technol. Lett. 17, 2128-2130 (2005).
[CrossRef]

2004 (1)

T. Bifano, P. Bierden, and J. Perreault, "Micromachined Deformable Mirrors for Dynamic Wavefront Control," Proc. SPIE 5553, 1-16 (2004).
[CrossRef]

2000 (1)

T. G. Bifano, J. A. Perreault, and P. A. Bierden "A micromachined deformable mirror for optical wavefront compensation," Proc. SPIE 4124, 7-14 (2000).
[CrossRef]

Bierden, P.

T. Bifano, P. Bierden, and J. Perreault, "Micromachined Deformable Mirrors for Dynamic Wavefront Control," Proc. SPIE 5553, 1-16 (2004).
[CrossRef]

Bierden, P. A.

T. G. Bifano, J. A. Perreault, and P. A. Bierden "A micromachined deformable mirror for optical wavefront compensation," Proc. SPIE 4124, 7-14 (2000).
[CrossRef]

Bifano, T.

Y. Zhou and T. Bifano, "Characterization of Contour Shapes Achievable with a MEMS Deformable Mirror," Proc. SPIE 6113, 123-130 (2006).

Y. Zhou and T. Bifano, "Adaptive optics using a MEMS deformable mirror," Proc. SPIE 6018, 350-356 (2005).

T. Bifano, P. Bierden, and J. Perreault, "Micromachined Deformable Mirrors for Dynamic Wavefront Control," Proc. SPIE 5553, 1-16 (2004).
[CrossRef]

Bifano, T. G.

T. G. Bifano, J. A. Perreault, and P. A. Bierden "A micromachined deformable mirror for optical wavefront compensation," Proc. SPIE 4124, 7-14 (2000).
[CrossRef]

Bland, R. E.

J. M. Roth, R. E. Bland, and S. I. Libby, "Large-Aperture Wide Field of View Optical Circulators," IEEE Photon. Technol. Lett. 17, 2128-2130 (2005).
[CrossRef]

Conrad, R. A.

Libby, S. I.

J. M. Roth, R. E. Bland, and S. I. Libby, "Large-Aperture Wide Field of View Optical Circulators," IEEE Photon. Technol. Lett. 17, 2128-2130 (2005).
[CrossRef]

Michael, S.

Murphy, R. J.

Perreault, J.

T. Bifano, P. Bierden, and J. Perreault, "Micromachined Deformable Mirrors for Dynamic Wavefront Control," Proc. SPIE 5553, 1-16 (2004).
[CrossRef]

Perreault, J. A.

T. G. Bifano, J. A. Perreault, and P. A. Bierden "A micromachined deformable mirror for optical wavefront compensation," Proc. SPIE 4124, 7-14 (2000).
[CrossRef]

Roth, J. M.

Wilcox, W. E.

Williams, T. H.

Zhou, Y.

Y. Zhou and T. Bifano, "Characterization of Contour Shapes Achievable with a MEMS Deformable Mirror," Proc. SPIE 6113, 123-130 (2006).

Y. Zhou and T. Bifano, "Adaptive optics using a MEMS deformable mirror," Proc. SPIE 6018, 350-356 (2005).

Appl. Opt. (1)

IEEE Photon. Technol. Lett. (1)

J. M. Roth, R. E. Bland, and S. I. Libby, "Large-Aperture Wide Field of View Optical Circulators," IEEE Photon. Technol. Lett. 17, 2128-2130 (2005).
[CrossRef]

Proc. SPIE (4)

Y. Zhou and T. Bifano, "Characterization of Contour Shapes Achievable with a MEMS Deformable Mirror," Proc. SPIE 6113, 123-130 (2006).

Y. Zhou and T. Bifano, "Adaptive optics using a MEMS deformable mirror," Proc. SPIE 6018, 350-356 (2005).

T. G. Bifano, J. A. Perreault, and P. A. Bierden "A micromachined deformable mirror for optical wavefront compensation," Proc. SPIE 4124, 7-14 (2000).
[CrossRef]

T. Bifano, P. Bierden, and J. Perreault, "Micromachined Deformable Mirrors for Dynamic Wavefront Control," Proc. SPIE 5553, 1-16 (2004).
[CrossRef]

Other (6)

J. M. Roth, R. J. Murphy, W. E. Wilcox, and R. A. Conrad, "Experimental Emulation of Air-to-Space Laser Communication Links," 2008 IEEE-LEOS Annual Meeting, 13 November 2008, Paper ThAA2, 886-7.

S. G. Lambert and W. L. Casey, Laser Communications in Space (Artech House, Norwood, MA, 1995), Chap. 3.

R. Parenti, R. J. Sasiela, L. C. Andrews, and R. L. Phillips, "Modeling the PDF for the irradiance of an uplink beam in the presence of beam wander," Proc. SPIE 6215, 621508.1-13 (2006).

J. Wyant, "Zernike Polynomials," http://www.optics.arizona.edu/jcwyant/Zernikes/ZernikeP lynomialsForTheWeb.pdf

R. A. Conrad, Impact of the Boundary Layer on Pointing and Tracking in Airborne Free-Space Laser Communication Links (Master’s Dissertation, Aeronautics & Astronautics Department, M.I.T., June 2008).
[PubMed]

S. Zheng, Tracking Algorithms Under Boundary Layer Effects for Free-Space Optical Communications (Master’s Dissertation, Department of Electrical Engineering & Computer Science, M.I.T., August 2007).

Supplementary Material (2)

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Figures (10)

Fig. 1.
Fig. 1.

Example of boundary-layer-induced optical path difference (OPD) variation across a 100-mm (4-in.) aperture for an airborne platform. Computational fluid dynamics simulation is for a hyper-hemispherical turret geometry, a 29-kft altitude, a Mach 0.7-aircraft velocity, and a view angle of 120° azimuth and 45° elevation.

Fig. 2.
Fig. 2.

Diagram showing integration of the boundary-layer emulator into a testbed system for evaluating air-to-space links in the presence of environmental impairments. The testbed is described further in Refs. 4 and 5. MEMS DM: micro-electro-mechanical systems de-formable mirror, QWP: quarter wave plate, PBS: polarization beam splitter, DRM: directional rotation module. The deformable mirror is used at normal incidence and requires the bidirectional signals to be co-polarized; the DRM allows the two directions of propagation to be separated into orthogonal polarizations, allowing polarization splitting to be used in the aircraft terminal to separate transmit and receive beams [6].

Fig. 3.
Fig. 3.

Photograph of deformable mirror installed in the laboratory testbed for evaluating air-to-space links in the presence of boundary-layer turbulence.

Fig. 4.
Fig. 4.

Reduction of native-tilt-corrected OPD image (left) to 12×12 actuator image (right) by sampling each actuator’s location of maximum influence (center).

Fig. 5.
Fig. 5.

Plot of displacement (top) and residuals (bottom) vs voltage for a representative DM actuator in the center of the mirror. Plot of displacement data includes second-order fit produced using polyfit.

Fig. 6.
Fig. 6.

Mean surface displacement (top), peak-to-valley wave-front error (bottom left), and root-mean-square (RMS) wave-front error (bottom right) using linearization look-up table method and 75% circular mask diameter. PV and RMS errors with respect to ideal, flat surface.

Fig. 7.
Fig. 7.

Comparison of ideal, desired surfaces (“Commanded”) and deformable mirror replicated surfaces measured on the Fizeau interferometer (“Reproduced”) for various Zernike terms. Colorbar units of OPD in waves at λ = 1.55 μm.

Fig. 8.
Fig. 8.

Experimental results of fringe patterns on the deformable mirror’s surface using an interferometer. The boundary layer is emulated for look angles at 45° elevation, 0° azimuth (left), 90° azimuth (center), and 180° azimuth (right). Video slowed down to 30 fps for easier viewing. [video, 3.9 MB]

Fig. 9.
Fig. 9.

Experimental results of beam break-up due to boundary-layer distortions. Focal plane images of beam for look angles of 45° elevation and 0° azimuth (left), 90° azimuth (center), and 180° azimuth (right). [video, 3.2 MB]

Fig. 10.
Fig. 10.

Framing performance of boundary-layer emulator. Output frequency versus BLE frame rate (top graph) showing expected down-conversion factor of 165 consistent with input time series. Peak tone output power level versus BLE frame rate (bottom graph) shows nearly flat frequency response well beyond the intended 2-kfps frame rate.

Tables (2)

Tables Icon

Table 1. RMS and peak-to-valley wave-front error using look-up table and various circular mask diameters. Error values in waves based on λ = 1.55 μm. Characterization performed over stated displacement ranges in 10-V increments; corresponding displacement increments ranged from 40 nm to 170 nm depending on voltage bias point (c.f., quadratic voltage response in Fig. 5). Mean errors represent averages of the errors observed over the applicable displacement range.

Tables Icon

Table 2. RMS errors between theoretical Zernike surface and experimentally-generated Zernike surface produced by the deformable mirror and measured using the Fizeau interferometer (λ = 1.55 μm). ρ and θ define radial coordinates for the wave-front shape.

Metrics