Liquid crystal beam directors for airborne free-space optical communications

Winker, Bruce K.; Mahajan, Milind; Hunwardsen, M.

doi:10.1109/aero.2004.1367946

Cited by 20 publications

(9 citation statements)

References 14 publications

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“…Several groups have demonstrated optical phased arrays, digital beam deflectors (based on prisms or gratings) and liquid crystal spatial light modulators for wavefront control [1][2][3][4][5][6][7]. Most of these devices exploit electrically controlled birefringence of liquid crystals as means of introducing optical phase delay.…”

Section: Introductionmentioning

confidence: 98%

Voltage calibration of dual-frequency liquid crystal devices for infrared beam steering applications

et al. 2005

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This paper addresses the use of liquid crystal devices for electro-optic infrared laser beam steering, such as liquid crystal optical phased arrays (OPAs) and digital beam deflectors (DBDs). In these devices, voltages are synchronously applied to different liquid crystal pixels to steer light, either by diffraction and/or refraction using birefringent prisms. Dual frequency liquid crystals provide an order of magnitude higher speed as compared to conventional nematic liquid crystals, at the cost of more complex addressing algorithms and control circuits. In order to optimize the optical performance of a liquid crystal device, the control voltages must be calibrated. This procedure involves adjustment of the control voltages while monitoring the optical efficiency, and must be done for both steady-state phase levels as well as transitions between phase levels. Manual voltage calibration is unrealistically time consuming for multi-channel beam steering devices. Computer based calibration algorithms for dual frequency liquid crystal devices are discussed, and results are presented for both steady state and dynamic voltage calibration procedures.

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Section: Introductionmentioning

confidence: 98%

Voltage calibration of dual-frequency liquid crystal devices for infrared beam steering applications

et al. 2005

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“…A non-mechanical beam steering approach is useful for various applications where the beam direction changes rapidly to random locations or when a system needs to be compact with good mechanical stabilities. Various approaches for non-mechanical beam steering have been reported [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], which include an optical phased array, a liquid crystal phase modulator, an electro-optic crystal deflector, an in-plane laser array, a photonic crystal laser, a phase-locked VCSEL and so on. The beam steering performance can be figured by a number of resolution-points N, which is defined as distinguishable spot counts in far-field patterns.…”

Section: Introductionmentioning

confidence: 99%

Virtually image phased array based on Bragg reflector waveguide for large-port optical switching

Koyama

2015

SPIE Proceedings

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We review a new type of dispersion elements based on a Bragg reflector waveguide, which provides a large angular dispersion of 1~2°/nm. The device functions as sub-wavelength virtually imaged phased array grating. We obtain a number of resolution-points (possible channel-count in demultiplexing) over 1,000. We demonstrate a large-scale wavelength switch based on a Bragg reflector waveguides array. The waveguides array has a small footprint of 2×4 mm 2 , but provides both ultra-large numbers (>100) of output-ports and wavelength-channels at the same time. Prospects for further increase in the wavelength channel count and output ports will be discussed.

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“…Traditional gimbals provide a mechanical pointing solution in which the elevation axis mirror is positioned along the azimuth axis of rotation. They require either domes or large conformal windows to achieve large fields-of-regard 3 . Risley prisms also have been used in beam director applications.…”

Section: Introductionmentioning

confidence: 99%

Compact optical gimbal as a conformal beam director for large field-of-regard lasercom applications

et al. 2015

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Laser communication offers advantages over traditional RF communication, including reduced size, weight, and power, higher data rates, and resistance to jamming. However, existing beam directors used for large field-of-regard lasercom terminals have limitations. Traditional gimbals require either domes or large conformal windows to achieve large fields of regard. Risley prism-based beam directors have temperature-and wavelength-dependent pointing necessitating tight temperature control and pointing correction techniques. Other methods, like liquid crystal optical phased array beam directors, have low transmittance and low technology readiness levels (TRLs). This paper presents a detailed design and preliminary performance results of a prototype Compact Optical Gimbal (COG) beam director that provides a 2 inch beam over a +/-65 o field-of-regard through a small (~12 inch) flat window. The COG differs from the traditional gimbal in that it includes three-axis steering with off-axis elevation and dither control, and a folded refractive afocal telescope incorporated into the body of the gimbal to minimize size. The COG's optical system does not have the pointing challenges characteristic of Risley prisms, and it utilizes high TRL components, including many commercial off-theshelf parts, to simplify implementation. The compact size and performance support a variety of beam steering applications and platforms.

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Liquid crystal beam directors for airborne free-space optical communications

Cited by 20 publications

References 14 publications

Voltage calibration of dual-frequency liquid crystal devices for infrared beam steering applications

Voltage calibration of dual-frequency liquid crystal devices for infrared beam steering applications

Virtually image phased array based on Bragg reflector waveguide for large-port optical switching

Compact optical gimbal as a conformal beam director for large field-of-regard lasercom applications

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