"; _cf_contextpath=""; _cf_ajaxscriptsrc="/cfthorscripts/ajax"; _cf_jsonprefix='//'; _cf_websocket_port=8578; _cf_flash_policy_port=1244; _cf_clientid='A4335FA3054B134158603F386F25B5DA';/* ]]> */
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Multi-Wave Liquid Crystal Variable Retarders / Wave Plates![]()
LCC1115-A Ø10 mm Clear Aperture, LCC1115-B Ø10 mm Clear Aperture, LCC25 Benchtop LC Controller KLC101 K-Cube™ LC Controller ![]() Please Wait Operating Principle![]() High Retardance ![]() Low Retardance In their nematic phase, liquid crystal molecules have an ordered orientation, which together with the stretched shape of the molecules creates an optical anisotropy. When an electric field is applied, the molecules align to the field and the level of birefringence is controlled by the tilting of the LC molecules.
Features
Thorlabs' Multi-Wave Liquid Crystal Variable Retarders (LCVR) use nematic liquid crystal cells to function as variable wave plates. The absence of moving parts provides quick switching times on the order of milliseconds (see the Switching Time tab for details). Our multi-wave retarders are AR coated for 350 - 700 nm, 650 - 1050 nm, or 1050 - 1700 nm and can reach up to >6λ retardance (see the Performance tab for transmission and retardance data). An LC cell spacer that is 30 µm thick in the LCC1115-A or 50 µm thick in the LCC1115-B and LCC1115-C aids each retarder in achieving its maximum retardance value. The retarders have Ø10 mm clear apertures with a 1" outer diameters, making them compatible with any of our Ø1" optics mounts for 8 mm thick optics. An engraved white line on the front of each housing marks the slow axis. Performance Operation Controllers
LC Retarder PerformanceIn their nematic phase, liquid crystals molecules have an ordered orientation, which together with the stretched shape of the molecules, creates an optical anisotropy. When an electric field is applied, the molecules align to the field and the level of effective retardance is controlled by the tilting of the LC molecules. To minimize effects due to ions in the material, an LC device must be driven using an alternating voltage. Our LCC25 and KLC101 controllers, sold below, are designed to minimize the DC bias in the driving signal in the operating range of 0 V to 25 V. Due to changes in the molecular polarizability, the LC material exhibits higher chromatic dispersion at short wavelengths and comparably small chromatic dispersion at long wavelengths. To account for this, we provide the retardance data at one or two select wavelengths within the product's wavelength range in the table to the right. Additionally, the LC retardation also depends on the temperature of the device. As temperature increases, the retardation decreases with it. However, as seen in the Switching Time tab, the switching speed of the LC improves at higher temperatures. Generally, the LC's refractive indices (both ordinary and extraordinary) change more drastically as temperature nears the LC's clearing temperature. As such, we choose to use materials with a high clearing temperature to minimize the temperature dependence when used at room temperature. Click Here to Download Retardance Data
![]() Click to Enlarge Graph shows variation in retardance over a period of 154 weeks. Long-Term StabilityOur liquid crystal retarders exhibit consistent performance over time. The graph to the right shows the retardance vs. voltage for one previous-generation LCC1112-A three-quarter wave retarder, driven by our LCC25 liquid crystal controller over 154 weeks. The retardance was tested once per week and varied only slightly over the testing period. For the complete set of data from testing each week, please click below to download the full data file. The graph below to the left shows that the retardance varies only slightly at a constant voltage, while the graph below to the right shows that the voltage varies only slightly at a constant retardance. Similar consistency in performance can also be expected for our other models of retarders. To maximize the long-term stability of our retarders, we recommend always using our LCC25 or KLC101 controllers. They are designed to reduce the DC voltage offset, thus minimizing charge buildup and maximizing stability. ![]() Click to Enlarge Switching Time Decreases with Smaller Retardance Changes LC Retarders Switching TimeLiquid crystal retarders feature a short switching time compared to mechanical variable wave plates due to the lack of moving parts. The switching time of a liquid crystal retarder depends on several variables, some of which are controlled in the manufacturing process, and some by the user. In general liquid crystal retarders will always switch faster when changing from a high to a low birefringence value. Additionally, the higher the operating temperature is, the faster the retarder will switch from one state to another due to the decreased viscosity at the higher temperature. For any given retarder, the switching speed will always be faster at higher voltages. The graph to the right depicts examples of switching between different voltages. If trying to achieve faster switching speed, we recommend using the retarder together with a fixed waveplate, to use the variable retarder at a higher voltage. In addition, the material's viscosity and hence the switching speed also depend on temperature of the LC material. As can be seen below, the switching speed can increase by as much as two times by heating the LC retarder. Our standard LC retarders are designed to work at temperatures of up to 45 °C, where they can still maintain the specified retardation. If additional speed is required, the retarders can work at temperatures up to 70 °C, but the maximum retardation value will be lower. The switching speed also is directly proportional to the thickness of the LC retarder, the rotational viscosity of the LC material, and the dielectric anisotropy of the LC material. However, since each of those variables affects other operating parameters as well, our LC retarders are designed to optimize overall performance, with a special emphasis on switching time. We also offer OEM and custom LC retarders optimized for other parameters, as well as faster liquid crystal retarders. Contact techsupport@thorlabs.com for details. Sample Switching Times at Various TemperaturesSwitching times were tested by measuring the rise time from V1 to V2 and the fall time from V2 to V1 with the liquid crystal retarder being held at the specified temperature. V1 was fixed in all of the tests and corresponds to the control voltage when the LC retarder is at 1 λ retardation. V2 is the voltage at the target retardation value. Please note that switching times at lower voltages (for instance, if V1=5 V) are longer than the switching times specified below. LCC1115-A
LCC1115-B
LCC1115-C
Drawing indicates the slow and fast axes AlignmentThe slow (extraordinary) axis of the liquid crystal retarder corresponds to the orientation of the long axis of the liquid crystal molecules when no voltage is being applied. Applying a voltage will cause the orientation direction of the liquid crystal molecules to rotate out of the plane of the drawing to the right, changing the retardation. Thorlabs LC retarders are nematic liquid crystal devices, which must be driven with an AC voltage in order to prevent the accumulation of ions and free charges, which degrades performance and can cause the device to burn out. In order to precisely align the axis of the liquid crystal cell, mount the retarder in an appropriate rotation mount (e.g. the RSP1(/M) or the CRM1P(/M) for our Ø10 mm clear aperture retarders and RSP2(/M) or the LCRM2(/M) for our Ø20 mm clear aperture retarders). Then set up a detector or power meter to monitor the transmission of a beam through a pair of crossed linear polarizers. Next place the LC retarder between two crossed polarizers with the slow axis aligned with the transmission axis of the first polarizer. Then slowly rotate it until the transmitted intensity is minimized. In this configuration, the LC retarder is ready for phase modulation applications. To operate as a light intensity modulator or shutter, again find the minimum transmitted intensity as prescribed above. Once the minimum is found, rotate the retarder by ±45°. This will maximize the transmitted intensity through the crossed polarizers for most LC retarders (e.g., zero-order quarter- or half-wave plates). However, this rule of thumb does not rigidly hold for multi-wave phase retarders using broadband sources due to the wavelength dependency of the retardation. ApplicationsPolarization Control with a Liquid Crystal Variable Retarder Pure Phase Retarder with Liquid Crystal Variable Retarder Thorlabs' Custom Liquid Crystal CapabilitiesThorlabs offers a large variety of liquid crystal retarders from stock, including 1/2-, 3/4-, full-wave, and multi-wave models with a Ø10 mm or Ø20 mm clear aperture as well as 1/2-wave temperature-controlled models. However, we also offer OEM and custom retarders. The retardance range, coating, rubbing angle, temperature stabilization, and size can be customized to meet many unique optical designs. We also offer other custom liquid crystal devices, such as empty LC cells, polarizaton rotators, and noise eaters. For more information about ordering a custom liquid crystal device, please contact Thorlabs' technical support. Our engineers work directly with our customers to discuss the specifications and other design aspects of a custom liquid crystal retarder. They will analyze both the design and feasibility to ensure the custom products are manufactured to high-quality standards and in a timely manner. Polyimide (PI) Coating and Rubbing - Custom Alignment Angle Custom Cell Spacing Here, δ is the retardance in waves, d is the thickness of the LC material, λν is the wavelength of light, and Δn is the birefringence of the LC material used. Thus, for a given wavelength, the retardance is determined by the wall spacing inside the LC cell (i.e., the thickness of LC layer). We offer standard retardance ranges of λ/2 to 30 nm, 3λ/4 to 30 nm, and λ to 30 nm, but higher retardance ranges may also be ordered. Custom Liquid Crystal Material Temperature Control/Switching Time Assembly / Housing Testing For More Information
![]() Click to Enlarge Figure 1: Patterned Retarder with Random Distribution Features
Applications
Thorlabs offers customizable patterned retarders, available in any pattern size from Ø100 µm to Ø2" and any substrate size from Ø5 mm to Ø2". These custom retarders are composed of an array of microretarders, each of which has a fast axis aligned to a different angle than its neighbor. The size and shape of the microretarders are also customizable. They can be as small as 30 µm and in shapes including circles and squares. This control over size and shape of the individual microretarders allows us to construct a large array of various patterned retarders to meet nearly any experimental or device need. These patterned retarders are constructed from our liquid crystals and liquid crystal polymers. Using photo alignment technology, we can secure the fast axis of each microretarder to any angle within a resolution of <1°. Figures 1 - 3 show examples of our patterned retarders. The figures represent measured results of the patterned retarder captured on an imaging polarimeter and demonstrate that the fast axis orientation of any one individual microretarder can be controlled deterministically and separately from its neighbors. The manufacturing process for our patterned retarders is controlled completely in house. It begins by preparing the substrate, which is typically N-BK7 or UV fused silica (although other glass substrates may be compatible as well). The substrate is then coated with a layer of photoalignment material and placed in our patterned retarder system where sections are exposed to linearly polarized light to set the fast axis of a microretarder. The area of the exposed sections depends on the desired size of the microretarder; the fast axis can be set between 0° and 180° with a resolution <1°. Once set, the liquid crystal cell is constructed by coating the device with a liquid crystal polymer and curing it with UV light. Thorlabs' LCP depolarizers provide one example of these patterned retarders. In principle, a truly randomized pattern may be used as a depolarizer, since it scrambles the input polarization spatially. However, such a pattern will also introduce a large amount of diffraction. For our depolarizers, we designed a linearly ramping fast axis angle and retardance that can depolarize both broadband and monochromatic beams down to diameters of 0.5 mm without introducing additional diffraction. For more details, see the webpage for our LCP depolarizers. By supplying Thorlabs with a drawing of the desired patterned retarder or an excel file of the fast axis distribution, we can construct almost any patterned retarder. For more information on creating a patterned retarder, please contact Tech Support. ![]() Click to Enlarge Figure 2: Patterned Retarder with a Spiral Distribution ![]() Click to Enlarge Figure 3: Patterned Retarder with a Pictoral Distribution
![]()
Thorlabs' Ø10 mm clear aperture, multi-wave liquid crystal retarders are available with AR coatings for 350 - 700 nm (LCC1115-A), 650 - 1050 nm (LCC1115-B), or 1050 - 1700 nm (LCC1115-C) light. They can provide a max retardance of >6λ. These retarders have an outer diameter of 1", making them compatible with any of our Ø1" optic mounts for 8 mm thick optics. As this retarder has a 1" outer diameter, it can be mounted using the RSP1(/M) Post-Mountable Rotation Mount or the CRM1P(/M) 30 mm Cage Rotation Mount. ![]()
The LCC25 and KLC101 Liquid Crystal (LC) Controllers are both designed to operate Thorlabs' liquid crystal cells, rotators, and retarders (except for the LCC2415-VIS, which has an integrated controller). Each controller supplies a a square-wave AC voltage output with an amplitude that can be adjusted from 0 Vrms to ±25 Vrms. Both will automatically detect and correct any DC offset to within ±10 mV in real time, helpful for increasing the life of liquid crystal devices. LCC25 Benchtop Controller Please visit the LCC25 controller page for more information on this controller's features. KLC101 K-Cube™ Controller Note that the KLC101 controller does not ship with a power supply. For applications requiring a single K-cube, the TPS002 power supply (sold below) can be used. We also offer USB controller hubs for use with multiple K-cubes. See the full KLC101 controller web presentation for more information on the features of this controller and its power supply options.
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|