Thorlabs Kurios® Liquid Crystal Tunable Bandpass Filters provide a continuously tunable center wavelength (CWL) in the 420 - 730 nm, 430 - 730 nm, or 650 - 1100 nm range. Most Kurios models have a fixed bandwidth for any given center wavelength. Alternatively, the K2VB1(/M) has user-selectable bandwidth settings of Narrow, Medium, and Wide. The switching time varies depending upon the initial and final wavelengths and on the Kurios' bandwidth setting (for K2VB1(/M) only). 


  • Tunable Optical Filters with Fully Programmable Sequences
  • Temperature-Controlled Head for Long-Term Stability
  • Ø20 mm or Ø35 mm Clear Aperture
  • Requires KURIOS2 Controller (Sold Separately Below)
  • Provides Local Control via the Front Panel and Remote Control via BNC and USB
  • Software and SDK Included (See Software Tab for Details)
  • Several Mounting Options
  • Three 8-32 (M4 x 0.7) Tapped Holes for Post Mounting
  • Internal SM1 (1.035"-40) or SM2 (2.035"-40) Threads on Both Sides
  • 4-40 Tapped Holes on Both Sides for 30 mm or 60 mm Cage Systems
  • Filters are Factory Calibrated and Include a Test Report (Click Here for a Sample Test Report)

The Kurios optical filters require the KURIOS2 controller for operation (sold separately below). It provides Trigger In, Trigger Out, and Analog In functionality, making these tunable optical bandpass filters ideal for applications that perform multispectral or hyperspectral imaging, as demonstrated in the image to the right. For example, they can be used in conjunction with a monochrome scientific CMOS camera to obtain images with a much higher accuracy for color representation than using a color CMOS camera with a Bayer mosaic. This technique produces true spectral imaging and can thus show spectral features that would otherwise be impossible to detect. 

Similar in construction to Lyot and Solc filters, Kurios filters consist primarily of liquid crystal cells that are sandwiched between polarizing elements. Their integrated design enables quick and vibrationless tuning. For added operational stability, a closed-loop temperature control servo is used to maintain the filter head's operating temperature. An LED on the filter head displays red when the head is warming up and green when it is ready to be used.

Wavelength Control with KURIOS2 Controller
The controller's front panel provides manual control of the center wavelength and enables programmable switching sequences. It also features three menu buttons that can be used to toggle through various operating modes. For the K2VB1(/M), the buttons toggle between Narrow, Medium, and Wide (the three selectable bandwidths), as well as beam-blocking mode ("Black"). For the fixed bandwidth models, the buttons toggle between the only bandwidth available and Black mode. 

The KURIOS2 controller also offers three BNC connectors (Trigger In, Trigger Out, and Analog In) that allow a Kurios filter to be synchronized with a wide range of other devices, such as scientific cameras and motion control stages. Each Kurios filter is factory calibrated and ships with a switching time map so that the user may optimize their system for the specific filter.

Transmission and Polarization
The liquid crystal optics in Kurios filters are not sensitive to the direction of propagation, allowing the filter to be used in either direction. The first element in the filter head is a linear polarizer and each face is marked with a white line (see the images to the left) that indicates the transmitted polarization direction. For maximum transmission, the input beam should be linearly polarized and aligned with this polarization axis. Please note that since Kurios filters are structured like Lyot and Solc filters, the polarization axis rotates by 90° through the filter head. To obtain the specified attenuation of out-of-band wavelengths, the input beam should be well collimated, since the filter head's field of view is ±6°.

A lens-tube-mounted hard-coated 750 nm shortpass filter is included with our K2WB1(/M), K2WL1(/M), K2XL1(/M), and K2VB1(/M) Tunable Filters for visible wavelengths. Use of this filter is recommended to protect the filter head components from excessive IR illumination.

A hyperspectral image of a root cell taken using the previous-generation
KURIOS-WB1. Two sample spectrums at the regions indicated are also shown.

Mounting Options
These tunable filters are post mountable via three 8-32 (M4 x 0.7) taps on the sides of the housing. In addition, four 4-40 tapped holes on the front and back faces provide compatibility with our 30 mm or 60 mm cage systems, depending on the model. The front and back faces of the housing are internally SM1- (1.035"-40) or SM2- (2.035"-40) threaded. These threads accommodate Ø1" or Ø2" lens tubes, respectively. To connect the K2WB1(/M) or K2VB1(/M) filter to a camera, use our SM1A39 SM1-to-C-Mount thread adapter together with an appropriate tube lens.

Available models:

Liquid Crystal Tunable Filters, Fixed Wide Bandwidth, Visible Wavelengths

  • Wavelength Range: 420 - 730 nm
  • Bandwidth at λ = 550 nm: 35 nm FWHM
  • Switching Time: <150 ms
  • Polarized Transmission at λ = 550 nm: 45%
  • Requires the KURIOS2 Controller 

Liquid Crystal Tunable Filter, Fixed Narrow Bandwidth, Visible Wavelengths

  • Wavelength Range: 430 - 730 nm
  • Bandwidth at λ = 550 nm: 10 nm FWHM
  • Switching Time: <250 ms
  • Polarized Transmission at λ = 550 nm: 17%
  • Requires the KURIOS2 Controller (Sold Separately Below)
  • See the Table to the Right and the Specs Tab Above for More Details
  • Liquid Crystal Tunable Filter, Fixed Bandwidth, NIR Wavelengths
  • Wavelength Range: 650 - 1100 nm
  • Bandwidth at λ = 850 nm: 17 nm FWHM
  • Switching Time: <760 ms
  • Polarized Transmission at λ = 850 nm: 44%
  • Requires the KURIOS2 Controller 

Liquid Crystal Tunable Filter, Selectable Bandwidth, Visible Wavelengths

  • Wavelength Range: 420 - 730 nm
  • Bandwidth at λ = 550 nm:
  • Narrow Setting: 10 nm FWHM
  • Medium Setting: 18 nm FWHM
  • Wide Setting: 32 nm FWHM
  • Switching Time Depends Upon Bandwidth and Initial and Final Wavelength:
  • Narrow Setting: <750 ms
  • Medium Setting: <500 ms
  • Wide Setting: <250 ms
  • Polarized Transmission at λ = 550 nm:
  • Narrow Setting: 13%
  • Medium Setting: 17%
  • Wide Setting: 20%
  • Requires the KURIOS2 Controller 

Liquid Crystal Tunable Filter Controller

  • Designed for Kurios Liquid Crystal Tunable Filter Heads
  • Compatible with Narrow, Medium, and Wide Passband Wavelengths
  • Includes Kurios Software Package for Remote Operation