Context:

Optimising new generations of components in the infrared is still a major challenge, and one of the limiting factors is the ability to carry out fine metrology of the spectrophotometric performance of components with sufficient dynamic range over the spectral range of interest.

The aim here is to quantify the spectral and angular variations in the specular and diffuse responses of optical components. The SALSA (Spectral and Angular Light Scattering characterisation Apparatus) instrument was developed by the Institut Fresnel's CONCEPT team to address this problem in the visible and near-infrared domains.  In its current configuration, the SALSA instrument can perform measurements of scattering patterns over the spectral range [400 nm - 1700 nm] with a spectral resolution of better than 0.3 nm and an angular resolution of up to 0.1°. The dynamic range of measurement is more than 12 decades, so the detection limit is of the order of OD 12 for optical density measurements and 10^-8 sr^-1, the level of scattering by air particles, for BSDF measurements. 

Previous R&T studies have recently assessed the feasibility of extending the measurement capabilities of the SALSA instrument into the mid-infrared (MIR). The results show that the new technologies available in terms of sensors and sources now make this development affordable and realistic, while maintaining an equivalent level of performance. In this thesis, we therefore propose to develop the MIR version of SALSA in order to enable metrology of scattered light and the performance of optical components in the [1.65µm - 4µm] spectral band.

II. Work programme:

A - Extension of the current instrument to the range [1.65 µm-2.4 µm].

The first part of the thesis will be dedicated to extending the current instrument to 2.4 µm. This can in fact be done on the basis of the current device. The source block currently emits from 400 nm to 2.4 µm, so access to this spectral range requires the addition of an extra detector, the integration of which will be the first stage of this thesis work. Calibration of the bench and initial representative measurements on MIR filters will then be carried out.

B - Sizing of SALSA MIR [2.4 µm-4 µm] 

The second part of the thesis will focus on the complete design of the bench and associated optics for the spectral range [2.4 µm - 4 µm]. In particular, the various emission and detection systems already identified will be tested and their performance quantified in order to simulate the entire optical bench. This work will lead to the choice of the various components of the bench and their supply.

C - Development of the bench SALSA MIR [2.4 µm-4 µm] 

The third part of the PhD will be dedicated to the implementation and calibration of the previously designed SALSA MIR bench, as well as to carrying out the first representative measurements.  

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For more Information about the topics and the co-financial partner (found by the lab !); 

contact Directeur de thèse - myriam.zerrad@fresnel.fr

Then, prepare a resume, a recent transcript and a reference letter from your M2 supervisor/ engineering school director and you will be ready to apply online  before March 14th, 2025 Midnight Paris time !

engineering school, skills in  physics and engineering, Optics, photonics, electromagnetism, instrumentation