Swift Liquid Crystal Principles
Meadowlark Optics next generation liquid crystal variable devices utilizes a new bulk stabilized polymer liquid crystal formulation. With switching speeds of less than a 150 microseconds in both directions our new “Swift” Liquid Crystal devices are perfect for applications where response time is critical.
Swift Liquid Crystal Technology
Liquid crystal polymer composite materials have been studied extensively is the past decades because of their intriguing physics and their potential application in robust, fast-switching liquid crystal devices. Meadowlark Optics has developed a novel fabrication process in which a polymer network is utilized to enhance the electro-optical performance of our liquid crystal devices.
Typical bulk liquid crystal devices, such as Meadowlark’s’LCVR, have response times that are governed by the bulk of the liquid crystal and are a function of cell gap.
As cell gap increases, switching times increase as the square of the thickness. This effect is due to molecular properties of the bulk liquid crystal material and the alignment layer of the cell (See Figure 4-6). The actual temporal electro-optical response of the cell has two components, (1) a very fast surface layer effect that occurs very close to the alignment layer and is on the order of microseconds and (2) a relatively slow response that occurs in the bulk of the material on the order of milliseconds. This second response dominates in a typical bulk liquid crystal device. Figure 4-17 (a) defines these two regions for a standard liquid crystal variable retarder cell. To overcome this effect the introduction of small amounts of polymer material into the bulk allow for a multitude of alignment surfaces for the liquid crystal material. This allows for alignment surface effects throughout the bulk of the cell (Figure 4-17 (b)). The addition of a polymer stabilizing material in the bulk essentially decouples the cell gap from the switching speed. The challenge to this type of device is now there are no means for uniform liquid crystalalignment in the bulk, such that after infiltration of polymermaterial; the liquid crystal is aligned in random fashion with no particular “fast-axis” for functional retarder devices. For liquid crystal alignment to occur Meadowlark Optics performs a mechanical shearing process on the devices that aligns the bulk liquid crystal material (Figure 4-17 (c)). Once this step is performed the cell is locked into place and sealed. This assembly process ensures excellent uniformity in alignment of the liquid crystal molecules and gives a retardance uniformity across the clear aperture of less than 20nm.
Meadowlark Optics Swift liquid crystal technologies can be used throughout the visible and near infrared region. While these devices, like all liquid crystal devices, are affected by temperature and wavelength changes, they can be calibrated to accommodate those differences. Each Swift liquid crystal variable retarder is supplied with retardance versus voltage performance data for your specified wavelength, while our shutter devices are provided with temporal performance data. A coaxial cable with mating connector is provided for easy attachment to one of our new high voltage power supply sources.