NEMATIC LIQUID CRYSTAL DEVICES
Liquid Crystal Modes
Modes correlate to the behavior mechanisms of liquid crystal devices. BVO manufactures nematic phase liquid crystal devices and each mode has its advantages.
Electronically Controlled Birefringence (ECB) Mode: Versatile tunable retarder. Analog control of LC molecule phase allows specific wavelength control. Products: variable retarders and modulators.
Optically Compensated Bend (Pi-cell) Mode: High speed modulator. Differs from ECB mode by having parallel aligned molecules reducing rotational torque, which increases switching speed. Products: fast optical shutters, rapid Lyot tunable filters.
Twisted Nematic (TN) Mode: Most achromatic variable attenuator. LC molecules have 90 degree twist due to orthogonal rubbed alignment layers resulting in polarization rotation to incoming polarized light. The rotation of LC is unwound as voltage is increased. Products: achromatic variable broadband attenuators.
Vertically Aligned (VA) Mode: Highest contrast ratio. LC molecules are vertically aligned with zero voltage with no residual birefringence due to pre-tilt. The result is an exceptional dark state. Products: high contrast variable attenuators.
Liquid Crystal Developmental Lab
• Highly Versatile – 25 Years Producing custom devices
• Manufacture 1mm thick LC cells using thin glass (0.5 mm)
• Large aperture devices up to 90mm in size
• Square or Round
• Design and Supply Compensation Films
Full Performance LC Device Characterization
• Speed / Response Time
• Insertion Loss
• Contrast Ratio
Handmade Small Volume Lots (1-500 units)
High Volume Production Lots (100-10,000 units)
Large Volume Production vs. Precision Devices – we do both
|OEM Volume LC Devices||Precision LC Devices|
|Price||Most economical – Higher volume||More expensive – Low volume|
|Production Method||Screen printed patterns (gaskets), large ITO coated panels of glass, patterned polyimide, spacer balls distributed over panels, LC wick filling, scribe & break parts||Each unit handmade. Polished fused silica substrates, spin coat polyimide, machine buff, robot gaskets & spacers, vacuum chamber LC filling, hand finish components|
|NRE||Yes||Possible, if materials not in stock|
|Specification Flexibility||Less. Initial cell design incorporates all specifications then mass manufactured. Cell mfg method dictates certain specs.||More. Handmade cells can incorporate custom specs-low wavefront distortion, AR coatings, high uniformity, cell gaps, LC|
|MOQ||> 100 units, decreases cost||1-100 units, maximizes flexibility|
|Geometries||Square, rectangular – up to 200mm max dimension, single ITO landing pad||Round, square – 75mm OD or 75mm x 75mm max, dual landings opposite sides|
|LC Device Thickness||1.0mm – 1.5mm||6.0mm – 12.0mm|
|Wavefront Distortion||3-4 waves per 25mm measured @ 632nm||Lambda/4 per 25mm measured @ 632nm|
|LC Modes||ECB, VAN, TN and Pi||ECB, VAN, TN and Pi|
Basic LC Cell Design Sub Heading
- ITO coated glass
- buffed polyimide for LC alignment
- liquid crystal sandwiched in between glass substrates
- transverse electric field to drive the LC molecules
LC Cell Integration with Mounts Sub Heading
- Temperature compensation mounts
- Stress birefringence caused by potting
- Environmental tolerances