Couches minces optiques

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In situ optical monitoring

Finally, the deposition of complex multilayer stacks with a higher and higher number of layers requires controlling the thickness of each layer with an increasing precision (typically sub-nanometer).

This can only be achieved by an in situ measurement of the evolution of their optical properties during deposition.
Specific optical systems have been developed and other are under development in order to achieve in situ measurement precision that equals and even exceeds the precision of ex situ best commercial spectrophotometers.
The design and fabrication of these systems uses modern and innovative elements such as diode pump white light sources, square core fibers, custom fiber optics bundles, speckle removers, low noise detectors, higher performances spectrometers...
New signal processing methods of the spectrally and temporally resolved measured signal allowed developing innovative and model free methods for the determination of the dispersion of the real and imaginary parts of the refractive index of the fabricated layers.