Abstract

A new type of light modulator, the deformable grating modulator, based on electrically controlling the amplitude of a micromachined phase grating is described. Mechanical motion of one quarter of a wavelength is sufficient for switching in this device. The small mechanical motion allows the use of structures with high mechanical resonance frequencies. We have developed a deformable grating modulator with a bandwidth of 1.8 MHz and a switching voltage of 3.2 V and have demonstrated modulation with 16 dB of contrast. Smaller devices with bandwidths of as much as 6.1 MHz and predicted switching voltages of less than 10 V were also fabricated.

© 1992 Optical Society of America

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References

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  1. K. E. Petersen, Proc. IEEE 70, 420 (1982).
    [CrossRef]
  2. L. J. Hornbeck, Proc. Soc. Photo-Opt. Instrum. Eng. 1150, 86 (1989).
  3. R. M. Boysel, Opt. Eng. 30, 1422 (1991).
    [CrossRef]
  4. K. Gustafson, B. Hok, J. Phys. E 21, 680 (1988).
    [CrossRef]
  5. P. A. Beck, S. M. Taylor, J. P. McVittie, S. A. Ahn, Mater. Res. Symp. Proc. 182, 207 (1990).
    [CrossRef]
  6. S. Timoshenko, Vibration Problems in Engineering, 2nd printing (Van Nostrand, New York, 1928).
  7. R. T. Howe, in Transducers ’87, Record of the Fourth International Conference on Solid-State Sensors and Actuators (Institute of Electrical and Electronics Engineers, New York, 1987), p. 843.

1991 (1)

R. M. Boysel, Opt. Eng. 30, 1422 (1991).
[CrossRef]

1990 (1)

P. A. Beck, S. M. Taylor, J. P. McVittie, S. A. Ahn, Mater. Res. Symp. Proc. 182, 207 (1990).
[CrossRef]

1989 (1)

L. J. Hornbeck, Proc. Soc. Photo-Opt. Instrum. Eng. 1150, 86 (1989).

1988 (1)

K. Gustafson, B. Hok, J. Phys. E 21, 680 (1988).
[CrossRef]

1982 (1)

K. E. Petersen, Proc. IEEE 70, 420 (1982).
[CrossRef]

Ahn, S. A.

P. A. Beck, S. M. Taylor, J. P. McVittie, S. A. Ahn, Mater. Res. Symp. Proc. 182, 207 (1990).
[CrossRef]

Beck, P. A.

P. A. Beck, S. M. Taylor, J. P. McVittie, S. A. Ahn, Mater. Res. Symp. Proc. 182, 207 (1990).
[CrossRef]

Boysel, R. M.

R. M. Boysel, Opt. Eng. 30, 1422 (1991).
[CrossRef]

Gustafson, K.

K. Gustafson, B. Hok, J. Phys. E 21, 680 (1988).
[CrossRef]

Hok, B.

K. Gustafson, B. Hok, J. Phys. E 21, 680 (1988).
[CrossRef]

Hornbeck, L. J.

L. J. Hornbeck, Proc. Soc. Photo-Opt. Instrum. Eng. 1150, 86 (1989).

Howe, R. T.

R. T. Howe, in Transducers ’87, Record of the Fourth International Conference on Solid-State Sensors and Actuators (Institute of Electrical and Electronics Engineers, New York, 1987), p. 843.

McVittie, J. P.

P. A. Beck, S. M. Taylor, J. P. McVittie, S. A. Ahn, Mater. Res. Symp. Proc. 182, 207 (1990).
[CrossRef]

Petersen, K. E.

K. E. Petersen, Proc. IEEE 70, 420 (1982).
[CrossRef]

Taylor, S. M.

P. A. Beck, S. M. Taylor, J. P. McVittie, S. A. Ahn, Mater. Res. Symp. Proc. 182, 207 (1990).
[CrossRef]

Timoshenko, S.

S. Timoshenko, Vibration Problems in Engineering, 2nd printing (Van Nostrand, New York, 1928).

J. Phys. E (1)

K. Gustafson, B. Hok, J. Phys. E 21, 680 (1988).
[CrossRef]

Mater. Res. Symp. Proc. (1)

P. A. Beck, S. M. Taylor, J. P. McVittie, S. A. Ahn, Mater. Res. Symp. Proc. 182, 207 (1990).
[CrossRef]

Opt. Eng. (1)

R. M. Boysel, Opt. Eng. 30, 1422 (1991).
[CrossRef]

Proc. IEEE (1)

K. E. Petersen, Proc. IEEE 70, 420 (1982).
[CrossRef]

Proc. Soc. Photo-Opt. Instrum. Eng. (1)

L. J. Hornbeck, Proc. Soc. Photo-Opt. Instrum. Eng. 1150, 86 (1989).

Other (2)

S. Timoshenko, Vibration Problems in Engineering, 2nd printing (Van Nostrand, New York, 1928).

R. T. Howe, in Transducers ’87, Record of the Fourth International Conference on Solid-State Sensors and Actuators (Institute of Electrical and Electronics Engineers, New York, 1987), p. 843.

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Figures (4)

Fig. 1
Fig. 1

Illustration of the operation of the DGM. The two figures to the left show cross sections along the periodicity of the grating, whereas single-grating elements are shown on the right. In the relaxed state (a) the individual beams are suspended above the surface, so the distance from the top of the beams to the substrate is one-half wavelength of the light. The grating amplitude is then 2π rad, and the light is reflected as from a flat mirror. When the beams are pulled down to the surface by an applied electrostatic force (b), the grating amplitude becomes π rad. In this case the incident light is diffracted into higher-order diffraction modes.

Fig. 2
Fig. 2

Scanning electron micrograph of a completed DGM. The beams in this modulator are 80 μm long and 1.5 μm wide. The total width of the device is 70 μm.

Fig. 3
Fig. 3

Resonance frequency as a function of beam length with the beamwidth as a parameter. The measured values are the observed ringing frequencies at a pressure of 150 mbars. The theoretical curve is found by modeling the beam as a vibrating string.

Fig. 4
Fig. 4

Eye diagram for a DGM with beams that are 120 μm long and 1.5 μm wide. The time scale is 500 ns/division, and the voltage scales are 2 V/division for the lower trace and 200 mV/division for the upper trace. The lower trace is the input to the DGM, with switching between 0 and −2.7 V. The upper trace shows the eye diagram received by the photoreceiver that detects the intensity in one of the first-order diffracted modes from the DGM. The damping of the ringing corresponds to a Q factor of 1.5 (normal atmosphere).

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