Half-Wave Liquid Crystal Retarders with Temperature Control
- Nematic Liquid Crystal Variable Wave Plates
- Thermally Stabilized to ±0.1 °C
- Ø10 mm Clear Aperture
- AR Coated for Visible, NIR, or IR Light
K-Cube™ LC Controller
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.
|Selection Guide for LC Retarders|
|Half Wave||Ø10 mm or Ø20 mm|
|Half Wave, Thermally Stabilized||Ø10 mm|
|Full Wave||Ø10 mm or Ø20 mm|
|Full Wave, Thermally Stabilized||Ø20 mm|
|Multi-Wave, Integrated Controller||Ø10 mm|
|Custom LC Retarders|
- Variable Wave Plate to Actively Control the Polarization State of Light
- Retardance Range: ~30 nm to λ/2
- Ø10 mm Clear Aperture
- Thermally Stabilized to ±0.1 °C (with TC200 Controller, sold Below)
- Surface Quality: 40-20 Scratch-Dig
- Retardance Uniformity: <λ/50 Over the Entire Clear Aperture
Thorlabs' Thermally Stabilized Half-Wave Liquid Crystal Variable Retarders (LCVR) use a nematic liquid crystal cell to function as a variable wave plate. The absence of moving parts provides quick switching times on the order of milliseconds (see the Switching Time tab for details). These liquid crystal retarders feature an integrated heater which will hold the temperature of the retarder constant to within ±0.1 °C when used with our TC200 temperature controller. Temperature stabilization provides constant retardance even if the ambient temperature changes and also allows for faster switching times. A Y-cable is provided, which allows these retarders to be used directly with one of our LC Controllers and our TC200 Temperature Controller (all available separately below).
AR coatings are available for three wavelength ranges: 350 - 700 nm, 650 - 1050 nm, or 1050 - 1700 nm (see the Performance tab for transmission and retardance data). These retarders feature a Ø10 mm clear aperture and have an external SM1 thread, making them compatible with any of our SM1 mounts and lens tubes.
These liquid crystal variable retarders provide excellent uniformity, low optical losses and low wavefront distortion. Our retarders also provide a quick switching time, a broad operating temperature range, and a broad wavelength range. Please see the Specs and LC Retarders tabs for complete details.
A Liquid Crystal Variable Retarder consists of a transparent cell filled with a solution of Liquid Crystal (LC) molecules and functions as a variable wave plate. The orientation of the LC molecules is determined by the alignment layer in the absence of an applied voltage. The alignment layer is composed of an organic polyimide (PI) coating whose molecules are aligned in the rubbing direction during manufacturing. Due to the birefringence of the LC material, this LC retarder acts as an optically anisotropic wave plate, with its slow axis, marked on the mechanical housing, parallel to the surface of the retarder. Two parallel inner faces of the cell wall are coated with a transparent conductive film so that a voltage can be applied across the cell. When an AC voltage is applied, the LC molecules will reorient from their default alignment according to the applied Vrms.
The LCC25 and KLC101 liquid crystal controllers provide active DC offset compensation while applying an AC voltage (0 to 25 Vrms). The DC offset compensation automatically zeros the DC bias across the LC device in order to counteract the buildup of charge. The TC200 temperature controller provides precise PID regulated control of temperature.
|Wavelength Range||350 - 700 nma||650 - 1050 nm||1050 - 1700 nm|
|Liquid Crystal Material||Nematic Liquid Crystal|
|Retardance Range||~30 nm to >λ/2|
|Clear Aperture||Ø10 mm|
|Surface Quality||40-20 Scratch-Dig|
|Beam Deviation||<5 arcmin|
|Switching Speed (Rise/Fall, Typical)b||10.2 ms / 310 µs @ 22 °C||31.3 ms / 704 µs @ 25.6 °C||95.8 ms / 1.81 ms @ 25.6 °C|
|Damage Threshold||Pulsed (ns)||1.0 J/cm2
(532 nm, 10 Hz, 8 ns, Ø200 µm)
(810 nm, 10 Hz, 7.6 ns, Ø234 µm)
(1542 nm, 10 Hz, 10 ns, Ø458 µm)
|Pulsed (fs)||0.01 J/cm2
(532 nm, 100 Hz, 76 fs, Ø162 µm)
(800 nm, 100 Hz, 36.4 fs, Ø189 µm)
(1550 nm, 100 Hz, 70 fs, Ø145 µm)
|AR Coating||Ravg < 0.5% at all Air-to-Glass Surfaces for Specified Wavelength Range|
|Wavefront Distortion||≤λ/4 (@635 nm)|
|Retardance Uniformity||< λ/50 over the Entire Clear Aperture|
|Housing Outer Diameter||1.20"|
|Housing Thickness||30.0 mm|
|Housing Threading||External SM1 (1.035"-40)|
|Storage Temperature||-30 to 70 °C|
|Operation Temperature||-20 to 45 °C|
|Compatible Mounts||RSP1 (RSP1/M), CRM1 (CRM1/M), CRM1P (CRM1P/M), KM100|
|Temperature Sensor||NTC 10 kΩ Thermistor|
|Heater Resistance||38.4 Ω ±10%|
|Heating Capacity (Typical)||15 Watts|
|Heating Current (Max)||625 mW (@ 15 W)|
|Recommended Heater Controller||TC200|
|Variable Full-Wave Retarder Performance Graphs|
|Item #||Wavelength Range||Retardance
@ 25 °C
|LCC1111T-A||350 - 700 nm||(635 nm)|
|LCC1111T-B||650 - 1050 nm||(780 nm)|
|LCC1111T-C||1050 - 1700 nm||(1550 nm)|
LC Retarder Performance
In 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.
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Graph shows variation in retardance over a period of 154 weeks.
Our 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.
LC Retarders Switching Time
Liquid 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. If faster switching speeds are desired, we recommend using the retarder together with a fixed wave plate so that the retarder can be used at a larger 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 up to 50 °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 is also 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 custom and OEM LC retarders optimized for other parameters, as well as faster liquid crystal retarders. See the Custom Capabilities tab above, or contact Tech Support for details.
Sample Switching Times at Various Temperatures
Switching 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 is fixed at 10 V for all the tests, and V2 is the voltage at which the retardation is the maximum specified value for the retarder (1/2 λ). Please note that switching times at lower voltages (for instance, if V1=5 V) are longer than the switching times specified below.
|Temperature||V1||V2||Rise Time||Fall Time|
|22 °C||10||1.26||10.2 ms||310 µs|
|45 °C||10||1.26||5.85 ms||211 µs|
|60 °C||10||1.26||5.05 ms||146 µs|
|70 °C||10||1.26||4.55 ms||126 µs|
|Temperature||V1||V2||Rise Time||Fall Time|
|25.6 °C||10||1.5||31.3 ms||704 µs|
|45 °C||10||1.5||20.7 ms||475 µs|
|60 °C||10||1.5||15.9 ms||241 µs|
|70 °C||10||1.5||14.4 ms||198 µs|
|Temperature||V1||V2||Rise Time||Fall Time|
|25.6 °C||10||1.6||95.8 ms||1.81 ms|
|45 °C||10||1.6||66.4 ms||1.16 ms|
|60 °C||10||1.6||49.7 ms||692 µs|
|70 °C||10||1.6||47.2 ms||671 µs|
The 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.
Polarization Control with a Liquid Crystal Variable Retarder
The LCVR can be effectively used as a variable zero-order wave plate over a broad spectrum of wavelengths. The optical axis of the LCVR is defined as the major axis of the liquid crystal molecules when no voltage is being applied to the cell, which are all aligned due to the LC alignment layer. When using the LCVR to control the polarization of a beam, the linearly polarized input beam should be aligned so that its polarization axis is oriented at an angle of 45° with respect to the optical axis of the LCVR in order to maximize the dynamic range of the optic. The schematic below shows how the output state of polarization will change as retardance is decreased (RMS voltage increased).
Pure Phase Retarder with Liquid Crystal Variable Retarder
In order to only effect the phase of the incident beam, the linearly polarized input beam must have its polarization axis aligned with the optical axis of the liquid crystal retarder. As Vrms is increased, the phase offset in the beam is decreased. Pure phase retarders are often used in interferometers to alter the optical path length of one arm of the interferometer with respect to the other. With an LCVR, this can be done actively.
|Damage Threshold Specifications|
|Item #||Laser Type||Damage Threshold|
|LCC1111T-A||Pulsed (ns)||1.0 J/cm2 (532 nm, 10 Hz, 8 ns, Ø200 µm)|
|Pulsed (fs)||0.01 J/cm2 (532 nm, 100 Hz, 76 fs, Ø162 µm)|
|LCC1111T-B||Pulsed (ns)||1.7 J/cm2 (810 nm, 10 Hz, 7.6 ns, Ø234 µm)|
|Pulsed (fs)||0.01 J/cm2 (800 nm, 100 Hz, 36.4 fs, Ø189 µm)|
|LCC1111T-C||Pulsed (ns)||1.2 J/cm2 (1542 nm, 10 Hz, 10 ns, Ø458 µm)|
|Pulsed (fs)||0.08 J/cm2 (1550 nm, 100 Hz, 70 fs, Ø145 µm)|
Damage Threshold Data for Thorlabs' Liquid Crystal Variable Retarders
The specifications to the right are measured data for Thorlabs' Liquid Crystal Variable Retarders.
Laser Induced Damage Threshold Tutorial
The following is a general overview of how laser induced damage thresholds are measured and how the values may be utilized in determining the appropriateness of an optic for a given application. When choosing optics, it is important to understand the Laser Induced Damage Threshold (LIDT) of the optics being used. The LIDT for an optic greatly depends on the type of laser you are using. Continuous wave (CW) lasers typically cause damage from thermal effects (absorption either in the coating or in the substrate). Pulsed lasers, on the other hand, often strip electrons from the lattice structure of an optic before causing thermal damage. Note that the guideline presented here assumes room temperature operation and optics in new condition (i.e., within scratch-dig spec, surface free of contamination, etc.). Because dust or other particles on the surface of an optic can cause damage at lower thresholds, we recommend keeping surfaces clean and free of debris. For more information on cleaning optics, please see our Optics Cleaning tutorial.
Thorlabs' LIDT testing is done in compliance with ISO/DIS 11254 and ISO 21254 specifications.
First, a low-power/energy beam is directed to the optic under test. The optic is exposed in 10 locations to this laser beam for 30 seconds (CW) or for a number of pulses (pulse repetition frequency specified). After exposure, the optic is examined by a microscope (~100X magnification) for any visible damage. The number of locations that are damaged at a particular power/energy level is recorded. Next, the power/energy is either increased or decreased and the optic is exposed at 10 new locations. This process is repeated until damage is observed. The damage threshold is then assigned to be the highest power/energy that the optic can withstand without causing damage. A histogram such as that below represents the testing of one BB1-E02 mirror.
The photograph above is a protected aluminum-coated mirror after LIDT testing. In this particular test, it handled 0.43 J/cm2 (1064 nm, 10 ns pulse, 10 Hz, Ø1.000 mm) before damage.
|Example Test Data|
|Fluence||# of Tested Locations||Locations with Damage||Locations Without Damage|
According to the test, the damage threshold of the mirror was 2.00 J/cm2 (532 nm, 10 ns pulse, 10 Hz, Ø0.803 mm). Please keep in mind that these tests are performed on clean optics, as dirt and contamination can significantly lower the damage threshold of a component. While the test results are only representative of one coating run, Thorlabs specifies damage threshold values that account for coating variances.
Continuous Wave and Long-Pulse Lasers
When an optic is damaged by a continuous wave (CW) laser, it is usually due to the melting of the surface as a result of absorbing the laser's energy or damage to the optical coating (antireflection) . Pulsed lasers with pulse lengths longer than 1 µs can be treated as CW lasers for LIDT discussions.
When pulse lengths are between 1 ns and 1 µs, laser-induced damage can occur either because of absorption or a dielectric breakdown (therefore, a user must check both CW and pulsed LIDT). Absorption is either due to an intrinsic property of the optic or due to surface irregularities; thus LIDT values are only valid for optics meeting or exceeding the surface quality specifications given by a manufacturer. While many optics can handle high power CW lasers, cemented (e.g., achromatic doublets) or highly absorptive (e.g., ND filters) optics tend to have lower CW damage thresholds. These lower thresholds are due to absorption or scattering in the cement or metal coating.
Pulsed lasers with high pulse repetition frequencies (PRF) may behave similarly to CW beams. Unfortunately, this is highly dependent on factors such as absorption and thermal diffusivity, so there is no reliable method for determining when a high PRF laser will damage an optic due to thermal effects. For beams with a high PRF both the average and peak powers must be compared to the equivalent CW power. Additionally, for highly transparent materials, there is little to no drop in the LIDT with increasing PRF.
In order to use the specified CW damage threshold of an optic, it is necessary to know the following:
- Wavelength of your laser
- Beam diameter of your beam (1/e2)
- Approximate intensity profile of your beam (e.g., Gaussian)
- Linear power density of your beam (total power divided by 1/e2 beam diameter)
Thorlabs expresses LIDT for CW lasers as a linear power density measured in W/cm. In this regime, the LIDT given as a linear power density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size, as demonstrated by the graph to the right. Average linear power density can be calculated using the equation below.
The calculation above assumes a uniform beam intensity profile. You must now consider hotspots in the beam or other non-uniform intensity profiles and roughly calculate a maximum power density. For reference, a Gaussian beam typically has a maximum power density that is twice that of the uniform beam (see lower right).
Now compare the maximum power density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately. A good rule of thumb is that the damage threshold has a linear relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 10 W/cm at 1310 nm scales to 5 W/cm at 655 nm):
While this rule of thumb provides a general trend, it is not a quantitative analysis of LIDT vs wavelength. In CW applications, for instance, damage scales more strongly with absorption in the coating and substrate, which does not necessarily scale well with wavelength. While the above procedure provides a good rule of thumb for LIDT values, please contact Tech Support if your wavelength is different from the specified LIDT wavelength. If your power density is less than the adjusted LIDT of the optic, then the optic should work for your application.
Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. The damage analysis will be carried out on a similar optic (customer's optic will not be damaged). Testing may result in additional costs or lead times. Contact Tech Support for more information.
As previously stated, pulsed lasers typically induce a different type of damage to the optic than CW lasers. Pulsed lasers often do not heat the optic enough to damage it; instead, pulsed lasers produce strong electric fields capable of inducing dielectric breakdown in the material. Unfortunately, it can be very difficult to compare the LIDT specification of an optic to your laser. There are multiple regimes in which a pulsed laser can damage an optic and this is based on the laser's pulse length. The highlighted columns in the table below outline the relevant pulse lengths for our specified LIDT values.
Pulses shorter than 10-9 s cannot be compared to our specified LIDT values with much reliability. In this ultra-short-pulse regime various mechanics, such as multiphoton-avalanche ionization, take over as the predominate damage mechanism . In contrast, pulses between 10-7 s and 10-4 s may cause damage to an optic either because of dielectric breakdown or thermal effects. This means that both CW and pulsed damage thresholds must be compared to the laser beam to determine whether the optic is suitable for your application.
|Pulse Duration||t < 10-9 s||10-9 < t < 10-7 s||10-7 < t < 10-4 s||t > 10-4 s|
|Damage Mechanism||Avalanche Ionization||Dielectric Breakdown||Dielectric Breakdown or Thermal||Thermal|
|Relevant Damage Specification||No Comparison (See Above)||Pulsed||Pulsed and CW||CW|
When comparing an LIDT specified for a pulsed laser to your laser, it is essential to know the following:
- Wavelength of your laser
- Energy density of your beam (total energy divided by 1/e2 area)
- Pulse length of your laser
- Pulse repetition frequency (prf) of your laser
- Beam diameter of your laser (1/e2 )
- Approximate intensity profile of your beam (e.g., Gaussian)
The energy density of your beam should be calculated in terms of J/cm2. The graph to the right shows why expressing the LIDT as an energy density provides the best metric for short pulse sources. In this regime, the LIDT given as an energy density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size. This calculation assumes a uniform beam intensity profile. You must now adjust this energy density to account for hotspots or other nonuniform intensity profiles and roughly calculate a maximum energy density. For reference a Gaussian beam typically has a maximum energy density that is twice that of the 1/e2 beam.
Now compare the maximum energy density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately . A good rule of thumb is that the damage threshold has an inverse square root relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 1 J/cm2 at 1064 nm scales to 0.7 J/cm2 at 532 nm):
You now have a wavelength-adjusted energy density, which you will use in the following step.
Beam diameter is also important to know when comparing damage thresholds. While the LIDT, when expressed in units of J/cm², scales independently of spot size; large beam sizes are more likely to illuminate a larger number of defects which can lead to greater variances in the LIDT . For data presented here, a <1 mm beam size was used to measure the LIDT. For beams sizes greater than 5 mm, the LIDT (J/cm2) will not scale independently of beam diameter due to the larger size beam exposing more defects.
The pulse length must now be compensated for. The longer the pulse duration, the more energy the optic can handle. For pulse widths between 1 - 100 ns, an approximation is as follows:
Use this formula to calculate the Adjusted LIDT for an optic based on your pulse length. If your maximum energy density is less than this adjusted LIDT maximum energy density, then the optic should be suitable for your application. Keep in mind that this calculation is only used for pulses between 10-9 s and 10-7 s. For pulses between 10-7 s and 10-4 s, the CW LIDT must also be checked before deeming the optic appropriate for your application.
Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. Contact Tech Support for more information.
 R. M. Wood, Optics and Laser Tech. 29, 517 (1998).
 Roger M. Wood, Laser-Induced Damage of Optical Materials (Institute of Physics Publishing, Philadelphia, PA, 2003).
 C. W. Carr et al., Phys. Rev. Lett. 91, 127402 (2003).
 N. Bloembergen, Appl. Opt. 12, 661 (1973).
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Liquid Crystal Cell Seal Application
Thorlabs' Custom Liquid Crystal Capabilities
Thorlabs offers a large variety of liquid crystal retarders from stock, including 1/2-, 3/4-, and full-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, polarization 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
In their nematic phase, liquid crystal molecules naturally align to an average orientation, which together with their stretched shape, creates an optical anisotropy, or direction-dependent optical effect. The orientation of the LC molecules in an LC cell, in the absence of an applied voltage, is determined by the alignment layer, created by the polyimide (PI) coating and rubbing angle. Rubbing creates grooves, which the liquid crystal molecules will align to. Users can choose any initial orientation of LC molecules by specifying the rubbing angle.
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Custom Liquid Crystal Cell Without Case
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Liquid Crystal Cell Filling in a Vacuum Chamber
Custom Cell Spacing
The wall spacing inside of the liquid crystal cell, which determines the thickness of LC material, can be customized during the manufacturing process. The retardance range of an LC cell is dependent on the LC material thickness:
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Custom Liquid Crystal Cell Test Setup
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Custom Liquid Crystal Cell Test Result
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
Customers can also provide their own liquid crystal material, and Thorlabs will use it to fill the liquid crystal cell. Since different liquid crystal materials have different birefringence values, varying the material enables a different retardance range.
Temperature Control/Switching Time
A temperature sensor can also be integrated into the LC variable retarder. Using a temperature controller, the temperature of the retarder can be actively stabilized to within ±0.1 °C. The viscosity of the liquid crystal material is lowered at higher temperatures, allowing the retarder to switch from one state to another due to the decreased viscosity. An active temperature control system can be used to heat the retarder, allowing it to operate at higher switching speeds.
Assembly / Housing
If desired, we can manufacture custom liquid crystal retarders without housings.
Each LC retarder is tested for birefringence, uniformity, and fast axis angle, using the measurement setup shown in the photo to the left. The equipment measures the 2-dimensional birefringence distribution using wave plates and a CCD camera. The image to the right shows a sample test result of a liquid crystal retarder, showing excellent uniformity.
For More Information
Contact Thorlabs' technical support for more information about our custom liquid crystal device options or to place an order.
|Custom Capability||Custom Specification|
|Patterned Retarder Size||Ø100 µm to Ø2"|
|Patterned Retarder Shape||Any|
|Microretarder Size||≥Ø30 µm|
|Microretarder Shape||Round or Square|
|Retardance Range @ 632.8 nm||50 to 550 nm|
|Substrate||N-BK7, UV Fused Silica, or Other Glass|
|Substrate Size||Ø5 mm to Ø2"|
|AR Coating||-A: 350 - 700 nm
-B: 650 - 1050 nm
-C: 1050 - 1700 nm
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Figure 1: Patterned Retarder with Random Distribution
- Build a Custom Microretarder
- Customize Size, Shape, and Substrate Material
- Retardance Range: 50 - 550 nm
- Fast Axis Resolution: <1º
- Retardance Fluctuations Under 30 nm
- 3D Displays
- Polarization Imaging
- Diffractive Optical Applications: Polarization Gratings, Polarimetry, and Beam Steering
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.
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Figure 2: Patterned Retarder with a Spiral Distribution
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Figure 3: Patterned Retarder with a Pictoral Distribution
- Ø10 mm Clear Aperture
- Thermally Stabilized to ±0.1 °C (with TC200 Controller)
- 1.20" Outer Diameter
- SM1 (1.035"-40) External Threading
- 3 Standard AR Coatings Available
Thorlabs' Ø10 mm clear aperture, temperature-stabilized liquid crystal retarders are available with AR coatings for 350 - 700 nm (LCC1111T-A), 650 - 1050 nm (LCC1111T-B), or 1050 - 1700 nm (LCC1111T-C). The temperature of our retarders can be controlled to ±0.1 °C using the recommended TC200 temperature controller (see graph to the right). Temperature stabilization provides constant retardance even if ambient temperature changes and also allows for faster switching times. A Y-cable is provided, which allows these retarders to be used directly with one of our LC Controllers and our TC200 Temperature Controller (all available separately below).
These retarders have an external SM1 thread, making them compatible with any of our internally threaded SM1 optic mounts. As this retarder has a 1.20" outer diameter, it can be mounted using the RSP1 Post-Mountable Rotation Mount or the CRM1P 30 mm Cage Rotation Mount.
- 0 to ±25 VAC Square-Wave Output Voltage
- LCC25: 2000 ± 5 Hz
- KLC101: Adjustable from 500 Hz to 10 kHz
- Internal and External Options for Modulating the Output Square-Wave Amplitude
- Edit Settings Using Device Panel or Control via USB Input from a PC
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
The LCC25 LC Controller produces a 2000 Hz square-wave AC voltage output. Both the front panel and USB interface allow the user to select two voltage levels, Voltage 1 and Voltage 2. When the LCC25 is operated in the constant voltage mode, the output of the controller will have an amplitude equal to either of the two set voltage levels. In Modulation mode, the amplitude of the 2,000 Hz square-wave output will switch between Voltage 1 and Voltage 2 at a frequency that can be set internally (0.5 Hz to 150 Hz) or triggered externally with a 0 to 5 V TTL input (0.5 Hz to 500 Hz). The LCC25 controller's software package also allows the user to define a voltage sequence by specifying a starting voltage, ending voltage, voltage step size, and dwell time.
Please visit the LCC25 controller page for more information on this controller's features.
KLC101 K-Cube™ Controller
The KLC101 K-Cube™ LC Controller is a part of Thorlabs' growing line of high-end, compact controllers. It supplies a square-wave AC output voltage with a user-set frequency from 500 Hz to 10 kHz and features a small 60.0 mm x 60.0 mm footprint. The controller can store two voltage and frequency combinations, PresetV1 and Preset V2, either of which can be selected as the output. Additionally, the controller top panel, software, and trigger ports allow the use to create customized output voltage sequences. The voltage can be set to switch between PresetV1 and PresetV2 at rates from 0.1 and 150 Hz using the top panel controls or software. When in this mode, one of the trigger ports will output a 5 V logic signal, with the high level indicating that the output is PresetV2 and the low level indicating the output is PresetV1. Alternatively, a trigger port can be used as an input for a 5 V logic signal to switch between PresetV1 and PresetV2. The software also enables Sequence and Sweep Modes. The Sequence tool can be used to set a sequence of output voltage amplitudes, frequencies, and step durations. In Sweep mode, the KLC101 controller will scan between user-set start and end voltages with a user-specified step size and step duration.
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.
|LCC25||0 to ±25 V RMS||1.0 mV||2,000 ± 5 Hz||0.5 to 150 Hz||0.5 to 500 Hz||10 V/µs||±10 mV||30 Minutes||15 mA||5 VDC|
|KLC101||500 Hz to 10 kHz||0.1 to 150 Hz||150 Hz (Max)||50 mA|
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Back Panel of the TC200 Heater Controller
- Heating from 20 °C to 200 °C
- User-Selectable Display Units (°F, °C, or K)
- Run Standalone or via Software
- Adjustable PID
- Compatible with Positive and Negative Temperature Coefficient Thermistors
The TC200(-EC) Heater Controller is a benchtop controller intended for use with resistive heating elements rated up to 18 W, including the GCH25-75 cell heater included with our Dichroic Atomic Vapor Spectroscopy Kit. The unit will display the temperature in either °F, °C, or K, and can be programmed for up to five sequential temperature settings along with associated ramp and hold times for each level. A user programmable maximum temperature limit provides protection to the device being heated and a user-programmable power limit protects the heating element from being over driven. Other safety features include an Open Sensor Alarm that will shut down the driver if the temperature sensing element is missing or becomes disconnected.
Capable of standalone operation from a simple keypad interface, the TC200 can be interfaced with a PC using a standard USB Type B connector using our TC200 Application Program, LabVIEW drivers, LabWindows drivers, or using a simple command-line interface from any terminal window.
The TC200 is shipped with a 120 VAC power cord for use in the US while the TC200-EC is shipped with a 230 VAC power cord for use in Europe. If you require a power cord for another country, please contact your local sales office.