Speaker: Dr. Lionel Clermont
Affiliation: CSL (Centre Spatial de Liège), Liège, Belgium
Title: Advanced stray light characterization in space optical instruments
Duration: 50 minutes
Abstract:
In the quest to develop ever-more advanced space telescopes, stray light (SL) increasingly emerges as a primary limiting factor. SL, which arises from ghost reflections and scattering, degrades image quality by reducing resolution and introducing artifacts. This is especially problematic for telescopes tasked with observing faint objects or small variations in their intensity. SL must be controlled by design and characterized experimentally prior to launch. However, we have reached the limits of the conventional methods. This talk will address this problem and the many challenges that it involves. In particular we will present the results of the SL control in the Metop-3MI instrument, for which we have stretched the capacities to their utmost extremes. Moreover, we will present the development of a novel method using a pulse laser illumination, the Time-of-Flight (ToF) characterization.
Speaker: Dr. Florent Défossez
Affiliation: MULTITEL, Mons, Belgium
Title: In situ and remote multi-gas detection with an OPO-based spectrometer
Duration: 30 minutes
Abstract:
Despite the availability of commercial multi-gas detectors, identifying unknown gases on-site in case of industrial accident like fire, remains challenging due to smoke's complex composition and detectors cross-sensitivity. Infrared laser spectroscopy, based on the measurements of ro-vibrational transitions of IR-active molecules, is a well-known technique inherently selective and capable of performing non-invasive and quantitative gas detection in harsh environments. In this talk, we will discuss infrared laser spectroscopy techniques for in situ and remote sensing, focusing on requirements for an infrared laser spectrometer for identifying and quantifying multiple gases at ppm levels. Specifically, we'll spotlight the use of a new picosecond mid-IR Optical Parametric Oscillator (OPO) based laser source and share the results obtained in the case of in situ and remote sensing measurements carried in the lab and on the field.
Speaker: Dr. Baptiste Fabre
Affiliation: Université de Bordeaux - Centre Lasers Intenses et Applications (CELIA), France
Title: Spectroscopic studies using high harmonic generation
Duration: 30 minutes
Abstract:
High-order harmonic generation, a non-linear process resulting from the interaction of an intense and ultrashort laser field with a dilute medium (atoms or molecules in the gas phase), can be used as a secondary source of XUV photons. At the same time, informations about the process itself are intrinsically encoded in this spectrum (amplitude, phase, polarisation). The study of these characteristics is known as harmonic spectroscopy. In this talk, I will present a selection of some high harmonic spectroscopy studies based on various observables and carried out over the last few years at CELIA.
Speaker: Dr. Alexis Libert
Affiliation: UCLouvain - BIRA-IASB, Belgium
Title: Design and fabrication of advanced lasers and spectrometers: towards molecular metrology
Duration: 30 minutes
Abstract:
Alexis Libert (1,2), Baptiste Fabre (3), Séverine Robert (1), Clément Lauzin (2)
1) Royal Belgian Institute for Space Aeronomy, B-1180 Uccle, Belgium
2) Institute of Condensed Matter and Nanosciences, Université catholique de Louvain,
B-1348 Louvain-la-Neuve, Belgium
3) Université de Bordeaux, CNRS, CEA, CELIA, UMR5107, F33405 Talence, France
Molecular spectroscopy is a fundamental tool in studying the structure, dynamics and interactions of molecules. It allows to derive important reference parameters later used for fundamental physics, planetology and chemical kinetics applications. It relies on the precise measurement of the quantity of absorbed photons and of the frequency of light. However, achieving accurate measurements over a broadband range has always been a challenge. Frequency combs, which provide a precisely spaced grid of frequencies spanning a broad spectrum, have emerged as invaluable tools for addressing this challenge in molecular spectroscopy. Any comb line can be expressed as follows:
where 
is the offset frequency, 
the frequency difference between adjacent comb modes and an integer. These two characteristic frequencies, which lie in the radiofrequency domain can be measured very precisely and phase locked with microwave frequency standards. When measuring the comb spectrum, eventually after its interaction with a gas sample, with enough resolution to resolve the different comb lines, the precision on the determination of the frequency axis is ultimately limited by the precision on the offset and repetition frequencies which can reach (dn/n~10-14).
In this talk, the design and fabrication of a frequency comb will be described. Details about the conditions these oscillators should fulfill to provide on the order of 80 million pulses per second, each of them having a duration of about 
seconds. The free space Ti:Sapphire femtosecond oscillator built in house at UCLouvain will support these points. Then we will present the next steps we are working on to transform this femtosecond laser into a stabilized frequency comb. We will also describe how we intend to use it to perform broadband molecular spectroscopy with metrological level of precision on the intensity and frequency axes. Finally, we will emphasize the gain of such light sources when coupled with Fourier transform spectrometers like the one we are currently building at BIRA-IASB.
Speaker: Olivier Malek
Affiliation: SIRRIS, Seraing, Belgium
Title: Ultra Short Pulsed Laser Texturing for Surface Functionalisation
Duration: 30 minutes
Abstract:
Ultrashort Pulsed Laser Texturing is a bio-inspired alternative to advanced coatings to create functional surfaces. In this presentation, we will elaborate how ultrashort pulsed lasers work, and why they are an ideal candidate to create textures. This is illustrated by a few cases such as ultra black surfaces for space applications, advanced selective coating removal and friction modification amongst others. In addition, it will be shown how laser textures can also significantly lower the environmental impact of the surface functionality application process. The presentation will end with an outlook for future research topics, with special attention to digital photonic manufacturing.
