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White Light Interferometer

White Light Interferometer

Our White Light Interferometer GOBI uses spectrally resolved interferometry to accurately 

measure the Group Delay Dispersion (GDD) of multi-layered ultrafast optics. The device

has been developed at the MaxPlanck-Institute of Quantum Optics (Garching, Germany) 

to characterize and refine some of the most advanced coatings to date [1-3]. Combining 

spectral with temporal information and the possibility to accumulate multiple passes over 

the same optic ensures reliable results with unique spectral coverage of up to 

250-1060 nm (UV/VIS/NIR version) and 900-2400 nm (IR version). Spectrally resolved

detection makes reference lasers together with any related test sample

restrictions on specific reflection or transmission bands obsolete. This opens 

the full spectral range to characterize even ultra-broadband or advanced 

narrowband coatings. The flexible optical setup can measure 

mirrors and transparent samples under angles of incidence variable between 

0 and 70 degrees.


 Key Product Features:

 Ultrabroad spectral coverage • 400-1060 nm (VIS/NIR basic version) • 250-1060 nm (UV/VIS/NIR version) • 900-2400 nm (IR version)

 Direct spectrally dispersed measurement with a spectrometer

 No need for reference lasers, no requirements on specific reflectivity

 s and p polarization (separately)

 Angle of incidence: 0° and 5-70°

 Measurement of single mirrors or mirror pairs

 Laptop and userfriendly software interface included

 Footprint 45 x 45 cm2

 Specifications: GOBI GOBI+ GOBIIR
 Spectral range VIS/NIR UV/VIS/NIR IR
 Wavelength range 400-1060 nm 250-1060 nm 900-2400 nm
 Spectral accuracy 1 nm 4 nm
 GDD accuracy ± 5 fs²
 Angle of incidence range 0° and 5-70°
 Polarization s and p (separately)
 Optics size 1 inch (other sizes upon request)
 Footprint 45 x 45 cm²

Gobi is based on a Michelson Interferometer with an incoherent white light (WL) source. Data is acquired by scanning the delay of one arm and spectrally record the evolving interference pattern. Fully automated analysis yields the spectral phase and GDD. The spectrometer directly provides the spectrally resolved information avoiding artefacts from time-domain reconstruction. It also provides an intrinsic calibration reference for the delay scan, so that no additional reference lasers are required. This makes GOBI suitable for any optics measurements in the detection range without the need to cover a reference laser wavelength in transmission or reflectance.


In contrast to other devices GOBI is able to resolve strong GDD oscillations. 

Note that differences between measured and theoretical curves reflect tolerances 

in the manufacturing process of the coatings.

Examples of GDD measurements with our White Light Interferometer GOBI, and comparison

to the theoretical design. 

(a) Ultrabroadband PC70 mirrors with our unique doubleangle design, 

measured at 5° and 19° angle of normal incidence, together with the average. 

(b) Pulse Compression Mirror PC1921 for the infrared. (c) High dispersive HD73 mirror with 

-3000 fs2 per bounce at 1030 nm.

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