Design and implementation of a laser-pumped neodymium-doped glasses amplifier providing infrared broad spectrum pulses of 1 J to 1 Hz
Description
The work presented in this thesis falls within the general framework of the preamplification of neodymium-doped, diode-pumped lasers. The objective of the thesis is to demonstrate the technical feasibility of a system based on the pumping of these glasses by laser and, allowing the amplification at 1H hz and up to the joule level, of a broad spectrum pulse centered at 1 μm. The demonstration requires the study and understanding of various physical phenomena such as spectroscopy of neodymium-doped glasses, laser pumping, thermo-mechanical effects and frequency drift amplification. Thus, we first conduct a literature and experimental search of the spectroscopic properties of neodymium-doped glasses. We demonstrate experimentally the existence of non-linear losses linked to pumping by a monochromatic pulse of strong fluences. We also highlight the existence of a linear loss related to the fact that, of all the ions excited on the pumping level, only a relaxed part on the metastable level where the energy is stored. The efficiency of this transfer is the quantum pumping efficiency. All the spectroscopic properties of neodymium-doped glasses make it possible to establish storage efficiencies of the absorbed energy. In parallel, we are studying the thermo-mechanical effects generated by the transformation of a fraction of the pumping energy into heat in the glasses. These effects are qualitatively described and experimentally demonstrated. Their influence on the amplification of a broad-spectrum pulse and on the extraction of stored energy is studied by the experimental realization of a mixed amplifier with neodymium-doped glasses operating in double pass. Models and numerical simulations are then validated by amplification experiments in this system. The extraction efficiency is then directly given by numerical calculation. Knowledge of the storage and extraction yields leads to the design of a regenerative cavity with a telescope and a large transverse mode. The assembly of the cavity is carried out with the objective of extracting from the system 400 mJ wide spectrum pulses at a repetition rate of 1 Hz. (author)
Abstract (French)
Les travaux presentes dans ce memoire se situent dans le cadre general de la preamplification des lasers a verres dopes neodyme et pompes par diodes laser. L'objectif de la these est de demontrer la faisabilite technique d'un systeme base sur le pompage de ces verres par laser et, permettant l'amplification a 1 Hz et jusqu'au niveau du joule, d'une impulsion a spectre large centre a 1 μm. La demonstration requiert l'etude et la comprehension de diverses phenomenes physiques comme la spectroscopie des verres dopes au neodyme, le pompage par laser, les effets thermo-mecaniques et l'amplification a derive de frequence. Ainsi, nous effectuons d'abord une recherche bibliographique et experimentale des proprietes spectroscopiques des verres dopes au neodyme. Nous demontrons experimentalement l'existence de pertes non lineaires liees au pompage par une impulsion monochromatique de fortes fluences. Nous mettons egalement en evidence l'existence d'une perte lineaire liee au fait que, sur l'ensemble des ions excites sur le niveau de pompage, seule une partie relaxe sur le niveau metastable ou l'energie est stockee. Le rendement de ce transfert est le rendement quantique de pompage. L'ensemble des proprietes spectroscopiques des verres dopes au neodyme permet d'etablir des rendements de stockage de l'energie absorbee. Nous etudions parallelement les effets thermo-mecaniques generes par la transformation en chaleur, d'une fraction de l'energie de pompage, dans les verres. Ces effets sont qualitativement decrits et mis en evidence experimentalement. Leur influence sur l'amplification d'une impulsion spectre large et, sur l'extraction de l'energie stockee, est etudiee par la realisation experimentale d'un amplificateur a melange de verres dopes au neodyme et fonctionnant en double passage. Des modeles et des simulations numeriques sont alors valides par des experiences d'amplification dans ce systeme. Le rendement d'extraction est alors directement donne par calcul numerique. La connaissance des rendements de stockage et d'extraction conduit au dimensionnement d'une cavite regenerative a telescope et a large mode transverse. Le montage de la cavite est realise dans l'objectif d'extraire du systeme des impulsions a large spectre de 400 mJ, a un taux de repetition de 1 Hz.Files
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Additional details
Additional titles
- Original title (French)
- Conception et realisation d'un amplificateur a verres dopes neodyme pompes par laser, delivrant des impulsions a large spectre de 1 J a 1 Hz dans l'infrarouge
Publishing Information
- Imprint Pagination
- 201 p.
- Report number
- FRCEA-TH--10909
INIS
- Country of Publication
- France
- Country of Input or Organization
- France
- INIS RN
- 52035717
- Subject category
- S46: INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; S70: PLASMA PHYSICS AND FUSION TECHNOLOGY;
- Resource subtype / Literary indicator
- Thesis
- Descriptors DEI
- AMPLIFICATION; COMPUTERIZED SIMULATION; DOPED MATERIALS; GLASS; NEODYMIUM; OPTICAL PUMPING
- Descriptors DEC
- ELEMENTS; MATERIALS; METALS; PUMPING; RARE EARTHS; SIMULATION
Optional Information
- Notes
- 142 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses