Create an Account  |   Log In

View All »Matching Part Numbers


Your Shopping Cart is Empty
         

Liquid Crystal Optical Beam Shutter / Variable Attenuator


  • Vibration Free with Fast Shutter Switching Speeds: ≤5 ms
  • High Transmission and High Contrast Ratio
    of Visible Wavelengths (420 - 700 nm)
  • Optical Shutter and Variable Attenuator Modes

LCC1620

Liquid Crystal Optical Shutter

Application Idea

LCC1620 Optical Shutter Mounted to a
1500M-GE-TE 1.4 Megapixel Scientific
CCD Camera with an SM1A39 Adapter

Related Items


Please Wait
LCTF Spectrum
Click to Enlarge

The front face of the LCC1620 shutter head. Both the back and front of the shutter are engraved with the transmission axis and both feature internal SM1 threads.

Polarization Window, Straight vs. Coiled
Click to Enlarge

The graph above shows the measured transmission through the shutter and contrast ratio as a function of wavelength. The shaded regions denote the wavelength range over which we guarantee the shutter will meet the specifications listed in the Specs tab. Performance outside the shaded regions will vary from lot to lot and is not guaranteed. For a raw data file and additional plots, please see the Graphs tab.

LCTF Spectrum
Click to Enlarge

The side view of the LCC1620 Liquid Crystal Shutter, showing the STATUS LED light and power connector.

Features

  • Liquid Crystal Optical Shutter and Variable Attenuator for 420 - 700 nm Light
  • Vibration-Free Device with No Moving Parts
  • High Average Transmittance (>60%) and Contrast Ratio (8000:1) Over Operating Wavelength Range
  • Shutter and Attenuator Modes
  • Fast Shutter Switching Speeds (Shutter Mode):
    • Opening: 5 ms
    • Closing: 1 ms
  • Post Mountable and 30 mm Cage System Compatible
  • SM1 (1.035"-40) Threaded for Compatiblity with Lens Tubes

Thorlabs’ Liquid Crystal (LC) Optical Shutter / Variable Attenuator incorporates a liquid crystal cell sandwiched between polarizing elements that is used to quickly change the transmission to either block or attenuate light propagating through the device. The shutter operates over the 420 to 700 nm wavelength range. The LCC1620(/M) optical shutter provides rapid and vibrationless (due to no moving parts) control over the intensity of light through the device. Due to its rapid switching capabilities, this LC optical shutter is ideal for imaging and precision illumination applications. It can be used either as an optical shutter to block/transmit a beam or as a variable attenuator. In shutter mode, it can open in 5 ms and close in 1 ms (see the Specs tab for more information). When in attenuator mode, the potentiometer on top of the shutter is used to set the attenuation level.

A switch on the top of the shutter allows the user to select the shutter or attenuator mode. In the shutter mode, the LCC1620 will act similarly to a mechanical shutter, either allowing the light through or blocking it completely. In the attenuator mode it will act as a variable attenuator with the attenuation level controlled by the knob on the top of the shutter. The shutter can be controlled, in both modes, manually by adjusting the knob on the top of the shutter or through an external signal via the SMC connector. In Shutter mode this external signal is a 0 - 5 V TTL signal, in Attenuator mode this external signal is a 0 - 5 V DC signal. An LED on the side of the shutter (labeled "STATUS") will indicate green when the shutter is transmitting light and red when it is completely blocking light.

This LC Shutter is capable of achieving switching speeds that are significantly faster than either our single-blade or diaphragm optical beam shutters. Additionally, it can be modulated to higher frequencies than either of the mechanical shutters. However, due to the wavelength limitations of the liquid crystal cells, for applications above 700 nm or below 420 nm, the mechanical shutters should be used instead. The mechanical shutters should also be considered for applications that require unpolarized light since the LC shutter utilizes polarizers as part of the liquid crystal cell design.

Transmission & Polarization
Because the LC shutter is made from liquid crystal cells and polarizers, it is not sensitive to the direction of propagation and may be used in either direction. However, each face is engraved with a white line (see image above) that indicates the polarization axis for the device. For maximum transmission, the input beam should be linearly polarized and aligned with the polarization axis of the shutter. It should be noted, however, that the shutter will rotate the polarization axis by 90° at the output. The shutter is compatible with unpolarized light, however, due to the polarizers inside the device, the total transmission will be greatly reduced (since half the light will be blocked by the first polarizer).

Mounting Options
The front and back faces of the housing are SM1 (1.035"-40) threaded, which is ideal for mounting filters or Ø1" lens tubes to the housing. Additionally, four 4-40 tapped holes on the front and back faces ensure compatibility with Thorlabs' 30 mm cage system. These shutters are post mountable via one of two 8-32 (M4) taps on the sides of the housing.

Item # LCC1620(/M)
Operating Wavelength Range 420 - 700 nm
Transmissiona (Shutter Mode, Avg.) >60%
Contrast Ratiob (Avg.) >8000:1
Laser Damage Threshold CWc 1 W/cm (532 nm, Ø0.471 mm)
Pulsed (ns) 0.1 J/cm2
Pulsed (fs) 0.02 J/cm2 (532 nm, 76 Hz, 100 fs, Ø162 µm)
Clear Aperture Ø20 mm
Surface Quality 40-20 Scratch-Dig
Max Incidence Angle ±5°
Switching Speed (in Shutter Mode)d Opening: 5 ms (Typ.)
Closing: 1 ms (Typ.)
Operating Frequency Rangee 0 - 50 Hz
Wavefront Distortion ≤λ/4 @ 633 nm
External Input SMC Connector, 0 - 5 V, 25 kΩ Input Impedance
Power Adapter 12 VDC / 1.25 A with Power Cord
AC Power Requirements 110 - 240 VAC, 47 - 63 Hz, 0.4 A
Mounting Two #8-32 (M4) Threaded Holes for Post Mounting
30 mm Cage System Compatible
Ø1" Lens Tube Compatible
Operating Temperature 15 to 60 °C
Dimension (L × W × H) 60 × 27 × 60 mm
(2.36" × 1.06" × 2.36")
  • For linearly polarized light with the axis of polarization aligned to the transmission axis of the shutter
  • The average contrast ratio is specified over the operating wavelength range. The contrast ratio is defined as the ratio of the transmitted light when the shutter is open by the transmitted light when the shutter is closed.
  • The power density of your beam should be calculated in terms of W/cm. For an explanation of why the linear power density provides the best metric for long pulse and CW sources, please see the Damage Thresholds tab.
  • In shutter mode with a 0 - 5 V TTL input from the EXT port. Opening time is defined as the time taken for the TTL signal to fall to 10% of the max TTL signal and the shutter transmission to rise to 90% of the total transmitted power, while closing time is defined as the time taken for the TTL signal rise to 90% of the max TTL signal and shutter transmission to fall to 10% of the total transmitted power.
  • In shutter mode with a 0 - 5 V TTL signal. The shutter can be driven at frequencies higher than 100 Hz with a reduced contrast ratio.

Polarization Window, Straight vs. Coiled
Click to Enlarge

The above is a diagram showing the timing of a TTL pulse (top) and the shutter response (bottom).

Shutter Timing Specifications
Diagram Keya Description Time (Typ.)
A-B Delay between the input pulse's rising edge at 90% and the initialization of shutter down to 90% 0.65 ms
B-C Falling edge from 90% to 10% 0.346 ms
A-C Delay between the input pulse's rising edge at 90% and shutter down to 10% 0.416 ms
D-E Delay between the input pulse's falling edge at 10% and initialization of the shutter rise to 10% 2.23 ms
E-F Rising Edge from 10% to 90% 3.24 ms
D-F Delay between the input pulse's falling edge at 10% and shutter rise to 90% 5.47 ms
  • The letters refer to the points shown on the image to the right. All values are specified at 25 °C, for timing at higher temperatures please see the Manual.

The graphs below represent the measured data sets for the LCC1620(/M) LC Optical Shutter. All data was obtained with linearly polarized light with the axis of polarization aligned to the transmission axis (marked by a white line on the face) of the shutter. The contrast ratio is defined as the ratio of the transmitted light when the shutter is open to the transmitted light when the shutter is closed.

Polarization Window, Straight vs. Coiled
Click to Enlarge

Click for Raw Data
The graph above shows the measured transmission through the shutter as a function of attenuation voltage, taken in Attenuator Mode. The attenuation voltage was set by an external voltage. Data for multiple wavelengths are shown.

Polarization Window, Straight vs. Coiled
Click to Enlarge

Click for Raw Data
The graph above shows the measured transmission through the shutter as a function of wavelength, taken in Attenuator Mode with the voltage set by an external source. Data for multiple attenuation voltages are shown.

Polarization Window, Straight vs. Coiled
Click to Enlarge

Click for Raw Data
The graph above shows the measured transmission through the shutter as a function of wavelength. Data for multiple temperatures are shown.

Polarization Window, Straight vs. Coiled
Click to Enlarge

Click for Raw Data
The graph above shows the measured transmission through the shutter as a function of wavelength. Data for multiple Angles of Incidence (AOI) are shown.

Polarization Window, Straight vs. Coiled
Click to Enlarge

Click for Raw Data
The graph above shows the measured transmission through the shutter and contrast ratio as a function of wavelength taken at 25 °C. The contrast ratio is defined as the ratio of the transmitted light when the shutter is open to the transmitted light when the shutter is closed.

Polarization Window, Straight vs. Coiled
Click to Enlarge

Click for Raw Data
The graph above shows the measured contrast ratio of the shutter as a function of wavelength. The contrast ratio is defined as the ratio of the transmitted light when the shutter is open to the transmitted light when the shutter is closed. Data for multiple temperatures are shown.

Polarization Window, Straight vs. Coiled
Click to Enlarge

Click for Raw Data
The graph above shows the measured contrast ratio of the shutter as a function of wavelength. The contrast ratio is defined as the ratio of the transmitted light when the shutter is open to the transmitted light when the shutter is closed. Data for multiple Angles of Incidence (AOI) are shown.

Polarization Window, Straight vs. Coiled
Click to Enlarge

Click for Raw Data
The graph above shows the measured normalized transmission through the shutter over a 20 hour period.

Contrast Ratio
Click to Enlarge

Click for Raw Data
The graph above shows the measured contrast ratio of the shutter as a function of frequency. The contrast ratio is defined as the ratio of the transmitted light when the shutter is open to the transmitted light when the shutter is closed.

Switching Time Stability
Click to Enlarge

Click for Raw Data
The graph above shows the stability of the shutter switching time over a 6 week period.

Shutter Selection Guide
Shutter TypeOpticalMechanicalMechanical Chopper
Single BladeDiaphragm
Modulation Frequency50 Hz MaxContinuous: Up to 10 Hz
Burst: Up to 25 Hz
Continuous: Up to 10 Hz
Burst: Up to 15 Hz
Up to 10 kHz (Depending on Blade)
Variable AttenuationYesNoNoNo
Custom ModulationTriggered and AnalogTriggeredTriggeredControlled by Chopper Speed, Always periodic
100% TransmissionNoYesYesYes
100% AttenuationNoYesYesYes
Clear ApertureØ20 mmØ1/2" or Ø1"Ø1"Dependent on Chopper Blade Configuration
Vibration/Noise FreeYesNoNoNo
IntegrationSM1-Threaded Aperture,
30 mm Cage Compatible,
and Tap for Post Mounting
SM05- or SM1-Threaded Aperture and
Thread Adapters for Post Mounting
SM1-Threaded Aperture and
30 mm Cage Compatible
Stand for Chopper
Wheel Included
Damage Threshold Specifications
Laser Type Damage Threshold
Pulsed (ns) 0.1 J/cm2
Pulsed (fs) 0.02 J/cm2 (532 nm, 76 Hz, 100 fs, Ø162 µm)
CWa 1 W/cm at 532 nm, Ø0.471 mm
  • The power density of your beam should be calculated in terms of W/cm. For an explanation of why the linear power density provides the best metric for long pulse and CW sources, please see the "Continuous Wave and Long-Pulse Lasers" section below.

Damage Threshold Data for Thorlabs' LC Shutters

The specifications to the right are measured data for Thorlabs' Liquid Crystal Shutters.

 

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.

Testing Method

Thorlabs' LIDT testing is done in compliance with ISO/DIS11254 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.

LIDT metallic 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.
LIDT BB1-E02
Example Test Data
Fluence # of Tested Locations Locations with Damage Locations Without Damage
1.50 J/cm2 10 0 10
1.75 J/cm2 10 0 10
2.00 J/cm2 10 0 10
2.25 J/cm2 10 1 9
3.00 J/cm2 10 1 9
5.00 J/cm2 10 9 1

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) [1]. 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.

Linear Power Density Scaling

LIDT in linear power density vs. pulse length and spot size. For long pulses to CW, linear power density becomes a constant with spot size. This graph was obtained from [1].

Intensity Distribution

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:

  1. Wavelength of your laser
  2. Beam diameter of your beam (1/e2)
  3. Approximate intensity profile of your beam (e.g., Gaussian)
  4. 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):

CW Wavelength Scaling

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.

Pulsed Lasers

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 [2]. 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:

Energy Density Scaling

LIDT in energy density vs. pulse length and spot size. For short pulses, energy density becomes a constant with spot size. This graph was obtained from [1].

  1. Wavelength of your laser
  2. Energy density of your beam (total energy divided by 1/e2 area)
  3. Pulse length of your laser
  4. Pulse repetition frequency (prf) of your laser
  5. Beam diameter of your laser (1/e2 )
  6. 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 [3]. 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):

Pulse Wavelength Scaling

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 [4]. 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:

Pulse Length Scaling

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.


[1] R. M. Wood, Optics and Laser Tech. 29, 517 (1998).
[2] Roger M. Wood, Laser-Induced Damage of Optical Materials (Institute of Physics Publishing, Philadelphia, PA, 2003).
[3] C. W. Carr et al., Phys. Rev. Lett. 91, 127402 (2003).
[4] N. Bloembergen, Appl. Opt. 12, 661 (1973).


Posted Comments:
emilio  (posted 2017-10-28 00:15:07.55)
Wish it was available in NIR.
nbayconich  (posted 2017-11-20 08:25:24.0)
Thank you for contacting Thorlabs. We can provide customized versions of these liquid crystal shutters in NIR. I will contact you directly with more information about our custom capabilities.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available / Ships
LCC1620 Support Documentation
LCC1620Customer Inspired! Liquid Crystal Shutter / Variable Attenuator, Ø20 mm, 420 - 700 nm, 8-32 Taps
$1,147.50
Today
+1 Qty Docs Part Number - Metric Price Available / Ships
LCC1620/M Support Documentation
LCC1620/MCustomer Inspired! Liquid Crystal Shutter / Variable Attenuator, Ø20 mm, 420 - 700 nm, M4 Taps
$1,147.50
Today
Log In  |   My Account  |   Contact Us  |   Careers  |   Privacy Policy  |   Home  |   FAQ  |   Site Index
Regional Websites: West Coast US | Europe | Asia | China | Japan
Copyright 1999-2018 Thorlabs, Inc.
Sales: 1-973-300-3000
Technical Support: 1-973-300-3000


High Quality Thorlabs Logo 1000px:Save this Image