Component Blog Posts

Calculating the Refractive Index of a Transparent Material with a QCL – Case Study

Johan Petit is a French research engineer at ONERA, the French aerospace lab, researching material characterization. In 2022, his project was to calculate the refractive index of a material using a prism for different infrared wavelengths of light. The refractive index of a material is a number that describes how fast a light beam travels through that material, and it is essential to know that number for several applications. In his setup, Johan shines a laser on a prism and rotates the prism until the reflected beam (on the back face of the prism) is collinear with the incident beam. When this is the case, Johan can easily calculate the refractive index from and angles (see fig. a).

diagram image showing an input and output beam, refracting, transmitting, and reflecting back through a prism for refractive index calculation
Fig. a) principle of the measurement using a QCL from mirSense for example

If the material is subject to changes in temperature, then the setup can also be used up to 1000°C and even more if needed.

For his experiment, Johan had first considered a broadly tunable QCL source. However, the price was much higher than the single wavelength QCL source offered by mirSense, and, in the end, a single wavelength source was good enough for the project’s scope, and this is why Johan Petit decided to purchase a QCL source from mirSense, in a turnkey version so that he could use a plug-and-play version in his lab.

image of an experimental setup with a prism within a furnace within a cooled chamber
fig. b) experimental setup: a cooled chamber around the furnace around the prism
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Have questions?

For additional contacts about the project, please contact:

Dr Johan Petit – Research Engineer

ONERA – The French Aerospace Lab – Centre de Châtillon

29 Avenue de la Division Leclerc – BP 72 – 92322 CHATILLON CEDEX