AI Content Index › Liquid Crystals › TN
TN Twisted Nematic Liquid Crystal
Mode: Twisted Nematic | Most Achromatic Variable Attenuator | Custom Manufactured
Variable Attenuator
Most Achromatic
Broadband VIS & NIR
Normal Black or White
To 90mm Aperture
Twisted Nematic (TN) liquid crystal cells are the most achromatic LC variable attenuator mode. LC molecules have a 90° twist due to orthogonally rubbed alignment layers — as linearly polarized light enters the cell, it rotates along the LC helical structure from front to back substrate. This rotation is broadband and achromatic, making TN cells ideal for variable attenuation across wide wavelength ranges. BVO produces TN cells in normally black mode (dark state at 0V) and normally white mode (light state at 0V) for both visible and NIR applications.
Most Achromatic
LC Mode for Attenuation
VIS & NIR
Wavelength Coverage
How TN Works
In a TN cell, the front and back glass substrates are rubbed orthogonally — creating a 90° twist in the LC molecule orientation through the cell. Linearly polarized light entering the cell rotates 90° following the helical LC structure (Mauguin condition). Because this rotation is a waveguiding effect rather than birefringence, it is inherently broadband and achromatic.
In normally black mode: polarizers are mounted parallel to each other on the outside of the cell. At 0V, the LC rotates polarization 90° — the output polarizer blocks the light (dark state). As voltage increases, the LC unwinds and light transmission increases. In normally white mode: polarizers are orthogonally mounted. At 0V the cell is fully transmitting; voltage increases attenuate the light.
The achromatic nature of TN rotation makes it the preferred mode for broadband visible and NIR variable attenuators where wavelength-independent attenuation is required.
Key Features
- Most achromatic LC mode — broadband variable attenuation across visible and NIR
- 90° LC polarization rotation via helical molecular structure — inherently broadband
- Normally black mode — dark at 0V (parallel polarizers), light at high voltage
- Normally white mode — light at 0V (crossed polarizers), dark at high voltage
- Smooth analog attenuation as a function of voltage
- NIR TN polarization rotators available for broadband NIR attenuation
- Custom apertures to 90mm — square or round
- 1mm thick LC cell, 0.5mm thin glass substrates
- Full characterization: speed, insertion loss, contrast ratio
- Prototype to volume production (1–10,000 units)
Device Specifications (Custom — Contact BVO)
| Parameter | Details |
|---|
| LC Mode | Twisted Nematic (TN) — 90° molecular twist, orthogonal alignment |
| Achromatic Performance | Most achromatic LC mode — broadband VIS and NIR |
| Normally Black Mode | Dark at 0V (parallel polarizers) — light increases with voltage |
| Normally White Mode | Light at 0V (crossed polarizers) — attenuates with voltage |
| Wavelength Range | Visible and NIR — custom to specification |
| Cell Thickness | ~1mm total (0.5mm thin glass substrates) |
| Max Aperture | 90mm |
| Shape | Square or round — custom geometry available |
| Characterization | Speed, insertion loss, contrast ratio |
| Volume | Prototype (1 unit) through high volume (10,000 units) |
| Zero DC Bias | Required — AC drive only |
Applications
Broadband Variable AttenuatorsPrimary application. Achromatic attenuation across visible or NIR wavelength bands where wavelength-independent transmission control is required.
NIR Variable AttenuatorsNIR TN polarization rotators for broadband NIR attenuation in imaging, sensing, and instrumentation systems at 700–1100 nm.
Laser Power ControlElectronically controlled laser beam attenuation. TN achromatic rotation works across multiple laser lines where ECB would require per-wavelength optimization.
Camera / Sensor Exposure ControlElectronic shutter and exposure control for cameras and imaging sensors requiring smooth, broadband intensity modulation.
Optical IsolationNormally black TN attenuator as an electronically controlled optical switch or shutter in broadband optical systems.
Scientific InstrumentationBroadband attenuation for spectroscopy, radiometry, and optical power control applications requiring achromatic behavior across wide wavelength ranges.
Contact Bolder Vision Optik
