Posted in | Optical Filters

Photon etc. LLTF Contrast - Supercontinuum Tunable Filter for High Sensitivity Spectroscopy and Precise Calibration

The Laser Line Tunable Filter (LLTF CONTRAST) is a non-dispersive patented (US patent 7557990) optical tunable bandpass filter based on volume Bragg gratings. It combines outstanding out-of-band rejection with an optical density higher than OD6 and a wideband tuning range across the visible (VIS) and infrared (NIR, SWIR) spectra. This supercontinuum filter can be customized to cover the entire 400 nm to 2500 nm spectral range with high resolution in wavelength.

Moreover, the LLTF exhibits remarkable versatility when integrated with supercontinuum sources, allowing for the generation of tunable excitation sources. No alignment or adjustment is required when connecting the optical tunable bandpass filter to a supercontinuum source. Such combinations unlock the potential for advanced spectroscopic techniques, including photoluminescence excitation (PLE), photoluminescence (PL), and Raman spectroscopy, enabling precise and insightful analyses.


Key Features

The key features of the LLTF Tunable Filter are:

  • Out-of-band rejection higher than OD 6 
  • Wide tuning range
  • Efficiency up to 60%
  • Free-space or fiber coupled
  • Easy and rapid installation
  • Intuitive control software
LLTF Contrast - Photon etc


The LLTF can be easily coupled to a supercontinuum laser, providing a tunable laser source (TLS) capable of delivering a quasi-monochromatic output across a wide spectral range from 400 nm to 2500 nm. This tool can be used in various experiments and research fields, including photoluminescence, absorption spectroscopy, hyperspectral imaging, instrument calibration, and more.

Characterization of dielectric thin film filters (OD of up to 12) [1]

A transmittance measurement setup using the LLTF is employed to obtain spectrally resolved characterization of dielectric thin film filters with optical densities from 0 to 12 in a spectral range covering 400 nm to 1000 nm.

Time-resolved photoluminescence (TRPL) on photovoltaic materials [2]

Metastable defects in CIGS solar cells can be characterized with time-resolved photoluminescence (TRPL). TRPL is a technique where the sample is excited with a pulsed light and the luminescence signal decay is analyzed as a function of time. The excitation source is produced by combining a supercontinuum source with an LLTF (ps resolution achieved). 

“The developed contactless characterization method was compared with classical current–voltage measurements. TRPL leads to a more complete understanding of the physics of metastable defects in terms of quantifying the shift in minority charge carriers dynamics that it induces.”

Spectral Response of Photodetectors

Combined with a supercontinuum source, the outstanding out-of-band rejection and the wide spectral range covered by the LLTF (400-1000 nm VIS, 1000-2300 nm SWIR, 400-2500 nm EXT IV) allow the precise calibration of a vast array of photodetectors including CCD, EMCCD, sCMOS, InGaAs, MCT and more. In addition to focal plane arrays, the supercontinuum tunable filter can be used to calibrate single-pixel detectors such as photodiodes (APD, SPD, etc.), photomultiplier tubes (PMTs), or any other photosensitive device within this spectral range.

Explore the various configurations and options available with Photon etc.

[1] Lequime, M., Liukaityte, S., Zerrad, M., & Amra, C. (2015). Ultra-wide-range measurements of thin-film filter optical density over the visible and near-infrared spectrum. In Optics Express (Vol. 23, Issue 20, p. 26863). The Optical Society.
[2] El-Hajje, G., Ory, D., Paire, M., Guillemoles, J.-F., & Lombez, L. (2016). Contactless characterization of metastable defects in Cu(In,Ga)Se 2 solar cells using time-resolved photoluminescence. In Solar Energy Materials and Solar Cells (Vol. 145, pp. 462–467). Elsevier BV.

Contact Photon etc. for more information on these applications: [email protected]

There are numerous possible LLTF configurations whose spectral range and bandwidth can be finely tuned to fit specific needs. The specifications below of several tried-and-tested standard models may serve as a starting point.

Technical Specifications



Spectral Range 400 to 1000 nm 1000 to 2300 nm
Bandwidth (FWHM) 1.5-2.7 nm 2.0-5.0 nm
Pointing Stability < 1 mm lateral displacement @ 1m from filter
Peak Transmission up to 60%
Wavelength Relative Resolution FWHM/8
Aperture Diameter ≤ 5 mm
Dimensions (L x W x H) 9'' x 6.3'' x 6.7''
23 cm x 16 cm x 17 cm
Operating Temperature 10 to 40°C
Storage Temperature 5 to 50°C
Software PHySpec™ included
Computer Connection USB 2.0 (compatible 1.1)
Power Supply 100 - 240 V, 50 - 60 Hz
Grating Damage Threshold > 100 kW/cm2 average power
> 5 GW/cm2 peak power @ 1064 nm, 8 ns
Options Free-space/Fibered Output
Order Filter
Calibration Module
FWHM < 0.4 nm

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