Abstract

We report on a method for high speed, large stroke phase modulation using dual frequency control of liquid crystals. Our system uses an all-electronic feedback system in order to simplify the control. We show half wave phase modulations of ~120Hz with the operating point varying over nearly the full dynamic range of the device, and demonstrate larger phase shifts (2.5 waves) at a frequency of 37Hz. For large phase shifts, the speeds are an order of magnitude faster than existing techniques.

© 2004 Optical Society of America

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References

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  1. G. D. Love, �??Liquid Crystal Adaptive Optics,�?? In Adaptive Optics Engineering Handbook, R. K. Tyson ed, (Marcel Dekker, New York, 1999)
    [CrossRef]
  2. P. J. Bos and K. R. Beran, �??The pi-cell, A Fast Liquid-Crystal Optical Switching Device,�?? Mol. Cryst. Liq. Cryst. 113, 329 (1984).
    [CrossRef]
  3. S. T. Wu and C. S. Wu, �??High-speed liquid-crystal modulators using transient nematic effect,�?? J. Appl. Phys. 65, 527 (1989).
    [CrossRef]
  4. C. R. Stein, �??A Two-Frequency Coincidence Addressing Scheme for Nematic-Liquid-Crystal Displays,�?? Appl. Phys. Lett. 19, 343 (1971).
    [CrossRef]
  5. H. K. Bücher, R.T. Klingbiel, and J.P. VanMeter �??Frequency-addressed liquid crystal field effect,�?? Appl. Phys. Lett. 25, 186 (1974).
    [CrossRef]
  6. D. Dayton, S. Browne, J. Gonglewski, and S. Restaino, �??Characterization and Control of a Multielement Dual-Frequency Liquid-Crystal Device for High-Speed Adaptive Optical Wave-Front Correction,�?? Appl. Opt. 40, 2345 (2001).
    [CrossRef]
  7. V. A. Dorezyuk, A.F. Naumov, V.I. Shmal�??gauzen, �??Control of liquid crystal correctors in adaptive optical systems,�?? Sov. Tech. Phys. 34, 1389 (1989).
  8. I. R. Guralnik, V. N. Belopukhov, G. D. Love, and A. F. Naumov, �??Interdependence of the electrical and optical properties of liquid crystals for phase modulation applications,�?? J. Appl. Phys. 87, 4069 (2000).
    [CrossRef]
  9. S. Esposito, G. Brusa, and D. Bonaccini, �??Liquid crystal wavefront correctors: computer simulation results,�?? In ICO-16 Conference on Active and Adaptive Optics, F. Merkle ed, (European Southern Observatory, Munich, 1993

Appl. Opt.

Appl. Phys. Lett.

C. R. Stein, �??A Two-Frequency Coincidence Addressing Scheme for Nematic-Liquid-Crystal Displays,�?? Appl. Phys. Lett. 19, 343 (1971).
[CrossRef]

H. K. Bücher, R.T. Klingbiel, and J.P. VanMeter �??Frequency-addressed liquid crystal field effect,�?? Appl. Phys. Lett. 25, 186 (1974).
[CrossRef]

J. Appl. Phys.

I. R. Guralnik, V. N. Belopukhov, G. D. Love, and A. F. Naumov, �??Interdependence of the electrical and optical properties of liquid crystals for phase modulation applications,�?? J. Appl. Phys. 87, 4069 (2000).
[CrossRef]

S. T. Wu and C. S. Wu, �??High-speed liquid-crystal modulators using transient nematic effect,�?? J. Appl. Phys. 65, 527 (1989).
[CrossRef]

Mol. Cryst. Liq. Cryst.

P. J. Bos and K. R. Beran, �??The pi-cell, A Fast Liquid-Crystal Optical Switching Device,�?? Mol. Cryst. Liq. Cryst. 113, 329 (1984).
[CrossRef]

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 (1989).

Other

S. Esposito, G. Brusa, and D. Bonaccini, �??Liquid crystal wavefront correctors: computer simulation results,�?? In ICO-16 Conference on Active and Adaptive Optics, F. Merkle ed, (European Southern Observatory, Munich, 1993

G. D. Love, �??Liquid Crystal Adaptive Optics,�?? In Adaptive Optics Engineering Handbook, R. K. Tyson ed, (Marcel Dekker, New York, 1999)
[CrossRef]

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Figures (5)

Fig. 1.
Fig. 1.

(a) A simple LC cell structure schematic, and (b) the approximate equivalent circuit, where C is the equivalent parallel capacitance and G is the equivalent conductance

Fig 2.
Fig 2.

Block diagram showing the simplified electronic closed loop system. The cell capacitance is measured and is compared to the control input to generate an error signal. A comparator, operating on inputs from the error signal and a saw-tooth generator, provides the appropriate mark-space ratio between the high and low frequency voltages to be applied to the LC cell.

Fig. 3.
Fig. 3.

Oscillogram illustrating high-speed large phase modulation with closed-loop control. Upper trace shows input (control) signal. Lower trace shows measured optical signal. The time-base is 5ms/division.

Fig. 4.
Fig. 4.

A comparison of maximum achievable phase shift, with respect to frequency, for LC1001 in closed loop dual frequency control (triangles) and LC-E49 using the transient nematic effect (diamonds).

Fig 5.
Fig 5.

A comparison of maximum frequency of operation for a half wave phase shift versus the center operating point (bias) on the phase-voltage range, for LC1001 operated with closed-loop dual frequency control (diamonds) and LC-E49 operating in transient nematic mode (triangles). A nominal operating point of zero is defined when the cell is fully on. Note different frequency axes for dual frequency and transient nematic results.

Tables (1)

Tables Icon

Table 1. Niopik LC1001 parameters.

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