Beam Steering with Liquid Crystal Polarization Gratings

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Key Features

  • Low size, weight, and power
  • Random-access scanning
  • Robust non-mechanical operation
  • Large apertures possible (>15cm)
  • Diffraction-limited wavefront quality
  • High diffraction efficiency (>99%)
  • Up to 80°×80° steering demonstrated
  • Demonstrated in VIS to MWIR
Meadowlark Optics’ Liquid Crystal Polarization Gratings utilize spatially varying birefringence to create highly efficient polarization-sensitive gratings. Circularly polarized light can be directed into either the +1 or -1 order depending on the handedness of the incident light. By using a stack of N LCPGs and half-waveplate switches, it is possible to steer to 2ᴺ discrete angles in 1-D or 2-D arrays.

Beam Steering with Liquid Crystal Polarization Gratings

Liquid crystal polarization gratings are also known as geometric phase gratings, Pancharatnam-Berry phase gratings, and diffractive waveplates. These transmissive gratings efficiently (> 99.5%) diffract circularly polarized light to either the first positive or negative order, based on the handedness of the incident light. By incorporating fast electro-optic half-wave polarization retarders to control the handedness of polarization, Meadowlark can develop custom LCPG devices and systems with a range of leading capabilities:

  • Wide-angle beam steering > 100°
  • Large apertures > 20 cm
  • Sub-millisecond switching times
  • Dramatically reduced size, weight, and power (SWaP) requirements
  • Random-access and inertia-less beam steering
  • Dynamic focusing also available

Non-Mechanical Steering for a Range of Aperture Sizes Meadowlark can build LCPGs and LC switches using thin 200 μm glass and with apertures ranging from 2 mm to 200 mm. Thin glass enables discrete steering to >1,000 revolvable angles with transmissive assemblies < 1 cm thick. Meanwhile the ability to steer large beams over large angles makes this approach unique among non-mechanical steering technologies for replacing large gimbals or steering large collection apertures in optical receiver paths.

CPG Steering for Lidar LCPG technology excels at non-mechanical beam steering for many narrowband sensors including lidar. To date, we have demonstrated LCPG beam steering for both coherent and direct detection lidars and both monostatic and bistatic architectures. Due to the ability to steer light in discrete steps over large angles, LCPG beam steering is particularly well suited to steering flash lidar systems and coherent doppler lidar wind sensing systems

Ordering Information – Contact Us for a Quote

ORDERING INFORMATION
Meadowlark can provide custom systems to meet your needs using the patented liquid crystal polarization grating (LCPG) beam steering technology. When contacting us for a quote, please provide:

•Clear Aperture (mm)

•Operating Wavelength (nm)

•1D or 2D Steering

•Number of Angles

•Maximum Steering Angle (°)

•Response Time/Switching Speed (ms)

•Housing/Mechanical Interface Requirements

•Description of Application & Additional Details

Don’t see what you’re looking for?

We also offer a commercial product line consisting of unmounted LCPGs without integrated anti-reflection (AR) coatings so that we can provide customers with the best price. Please contact our knowledgeable Solutions Engineers regarding custom options, including custom diffraction angles, aperture sizes, and wavelengths through the visible to midwave infrared.

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Beam Steering with Liquid Crystal Polarization Gratings

Fundamentals
Liquid crystal polarization gratings (PGs) are fascinating optical components that differ from traditional diffraction gratings, like ruled, Bragg, or holographic gratings. In particular, PGs exhibit polarization sensitivity, can have diffraction efficiency approaching 100%, and are much less sensitive to incident angle than, for example, Bragg or volume holographic gratings. To understand how this is possible, it is important to first understand how PGs work.

Graphs & Figures

These plots show typical zero-order leakage spectra for different LCPG specifications. The LCPG diffraction efficiency is highest where the zero-order leakage is at a minimum.

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