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Chromatis™ production-grade test instrument is designed specifically to measure group delay dispersion in optical components for femtosecond applications.  It is a broadband optical test instrument that quickly and accurately characterizes the full dispersive properties of optical components and coatings.  Carefully managing optical dispersion is critical for optimal performance of ultrafast laser systems, multi-layer mirrors, and multiple quantum well structures.  Chromatis is user friendly, self-calibrating, and highly accurate.


  • Validating coating designs
  • Incoming optics inspection
  • Metrology for QA/QC

Read the Photonics Spectra article on Chromatis:

GDD Measurements

KMLabs’ Chromatis instrument was used for judging the SPIE Damage Symposium Thin Film Coating Competition in 2015 and 2016.  Results for 2015 and 2016 are available through SPIE.

Laser Damage

Key performance parameters of the Chromatis instrument include:

  • Group Delay Dispersion (GDD) accuracy:  ± 5 fs²
  • Measurement of both polarizations simultaneously
  • Rapid measurements – typically a few seconds per optic
  • He-Ne reference laser for automated, built-in self-calibration of every measurement.  Chromatis does not use a spectrometer, and no spectrometer calibration is necessary
  • Standard designs for 1” and 2″ diameter optics, highly repeatable fixtures and opto-mechanical referencing
  • Precision fixtures available for:
    1. 0° Angle of Incidence (AOI) in Reflection
    2. 5° – 70° AOI in Reflection
    3. 0° -70° AOI in Transmission
    4. Mirror pair measurement with variable AOI  (6° -54°) (available as upgrade option)
  • Reference optics for reflection and transmission modes of operation
  • Three user-replaceable detector modules (Silicon module included with standard system):
    1. Silicon:  500 nm – 1100 nm
    2. InGaAs:  1000 nm – 1650 nm (available as upgrade option)
    3. PbS: 1400 nm – 2200 nm (available as an upgrade option)
  • Simple, intuitive graphical user interface for technicians or power users.  Generate and customize your measurement reports.
  • Laptop computer included, with pre-installed measurement and control software
  • On-site installation and training visit available as upgrade option.
  • Customized measurement configurations available

The example below shows where a coating company wanted to make a coating with a fixed amount of GDD over a wavelength range around 1030nm.  KMLabs Chromatis was invaluable in the optimization of GDD for this coating design.

Coating Dispersion Graph

Featured Applications:

Low Group Delay Dispersion Optical Coating for Broad Bandwidth High Reflection at 45° Incidence, P Polarization of Femtosecond Pulses with 900 nm Center Wavelength

Advances in thin film coating have been critical in the further development of ultrafast laser science. The very high damage threshold of thin-film coated dielectric optics has allowed the manipulation and transport of high energy and high power, ultra-intense laser pulses. In order to maintain the short pulse durations, the phase introduced by the multi-layer stacks needs to be carefully designed and then carefully manufactured. Characterization of these optics is essential to ensure design specs are met.

In this work, the authors design and fabricate broadband laser mirrors to be used on petawatt class lasers. A KM Labs Chromatis, dispersion measurement device is used to characterize the GDD of the mirrors, showing that GDD remains below 100fs^2 over the HR band, which is only a small deviation from the design parameters.

Laser damage properties of broadband low-dispersion mirrors in sub-nanosecond laser pulse

The emergence of petawatt-class laser systems around the world is motivating more research and design of the multi-layer mirrors used to steer and manipulate these extreme laser beams. These petawatt systems are intrinsically ultra-fast laser systems, so design of these optics needs to optimize both the laser damage properties of the mirrors, as well as their phase response.

In this work, the authors design Ta2O5-HfO2/SiO2 composite quarter-wave and non-quarter-wave HfO2/SiO2 BBLD mirrors for a 30fs petawatt laser system. Laser damage of the optics are characterized by scanning electron microscope whereas the phase response (GDD) is characterized with a KM Labs Chromatis device. The Ta2O5-HfO2/SiO2 mirrors are found to outperform the HfO2/SiO2 mirrors.

Optimizing dispersion curve of mirrors for use in a high-power OPO

Chromatis – Dispersion Measurement

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