Nonlinear light scattering in a two component medium: optical limiting application
Description
Scattering is a fundamental manifestation of the interaction between matter and radiation, resulting from inhomogeneities in the refractive index, which decrease transmission. This phenomenon is then especially attractive for sensor protection from laser light by optical limiting. One of the methods to induce scattering at high incident energy is to make use of the Kerr effect where the index of refraction is intensity dependent. Thus, the idea is to use a two component medium with a good index matching between the two components at low intensity, resulting in the medium transparency, and to modify it, at high intensity, due to the non linearity of one component making the medium highly scattering. Some of the experimental and theoretical investigations concerning a new material (here, a cell containing some liquid with small silica particles as inclusion in it) are presented in the visible domain (I=532 nm), for the nanosecond protection regime, beginning, with the chemical synthesis of the sample. The experimental results concerning the optical limiting process are presented, showing that nonlinear scattering is clearly the dominant mechanism in confrontation with other potential nonlinear effects. Several complementary experiments are then performed to complete the nonlinear scattering characterization, involving the measurement of the angular distribution of scattered energy and the integrating sphere measurement. Further information are also gained by studying the time response of the nonlinearities with a dual-beam (pulsed-pump, cw probe) technique. The previous experimental data is also analyzed with some simple theoretical models to evaluate the nonlinearity of the material from optical limiting, the angular scattering and the total scattering energy measurements. The good match between all the analytical results permits to delineate the physical mechanisms responsible for the nonlinear scattering effect and to direct the final conclusion. (author)
Abstract (French)
Les protections de systemes d'observation dites auto-activees utilisent les proprietes optiques non lineaires de la matiere pour limiter l'intensite transmise par le systeme, lors d'impulsions laser intenses nanosecondes. Parmi les principaux effets de l'interaction matiere rayonnement utiles a cette limitation, se trouve une propriete encore peu utilisee dans ce domaine d'application: la diffusion optique non lineaire. La presente etude a pour objet l'elaboration et la caracterisation a la fois experimentale et theorique, d'un nouveau type de materiau utilisant, pour la protection, la diffusion par desadaptation d'indice. Le principe repose en effet sur un materiau constitue de deux composants (ici un milieu contenant des particules spheriques en inclusion) rendus optiquement homogenes par accord d'indice, et devenant diffusant du fait des non linearites induites a haute energie. Experimentalement, apres la synthese chimique du materiau. l'etude de la limitation a proprement parler permet de montrer la diffusion non lineaire a l'origine de l'effet observe. Des experiences supplementaires viennen ensuite completer la caracterisation de cette diffusion. Ainsi, la mesure des lobes de diffusion definit la repartition spatiale de l'energie diffusee. Une experience utilisant une sphere integrante permet l'estimation de la quantite totale d'energie perdue par diffusion. Enfin, la dynamique des differents phenomenes mis en jeu dans le processus de diffusion non lineaire est determinee au moyen d'une experience pompe-sonde. Un modele theorique simple de la propagation en regime non lineaire a ete developpe. Il permet de simuler l'influence sur la limitation des parametres constituant le materiau (notamment lorsqu'elIe est maximale), mais surtout d'avoir une premiere estimation des nonlinearites suscitees, par confrontation avec les resultats experimentaux obtenus. D'autres verifications theoriques indispensables viennent ensuite completer cette evaluation, suivie par l'interpretation des lobes de diffusion et des resultats de la sphere integrante. Dans tous les cas, ils permettentt d'etablir de nouvelles hypotheses sur l'origine des non-linearites presentes, en quantifiant l'importance relative des differents phenomenes mis en jeu dans le processus de diffusion non lineaireFiles
48078414.pdf
Files
(14.2 MB)
| Name | Size | Download all |
|---|---|---|
|
md5:5ac684662d48bcb56384fb4f5a58bad3
|
14.2 MB | Preview Download |
Additional details
Additional titles
- Original title (French)
- Etude de la diffusion non lineaire et de sa contribution a la limitation optique
Identifiers
Publishing Information
- Imprint Pagination
- 207 p.
- Report number
- FRNC-TH--9793
INIS
- Country of Publication
- France
- Country of Input or Organization
- France
- INIS RN
- 48078414
- Subject category
- S71: CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS;
- Resource subtype / Literary indicator
- Thesis
- Descriptors DEI
- ANGULAR DISTRIBUTION; KERR EFFECT; LASERS; NONLINEAR PROBLEMS; REFRACTIVE INDEX; SCATTERING; SENSORS
- Descriptors DEC
- DIELECTRIC PROPERTIES; DISTRIBUTION; ELECTRICAL PROPERTIES; OPTICAL PROPERTIES; PHYSICAL PROPERTIES
Optional Information
- Notes
- 64 refs.; Available from the INIS Liaison Officer for France, see the 'INIS contacts' section of the INIS-NKM website for current contact and E-mail addresses: http://www.iaea.org/inis/Contacts/; Also available from Bibliotheque Centrale, Route de Saclay, 91128 Palaiseau (France)