PhD thesis (HAL archive)

Directeur: Patrice CAMY, co-encadrant: Pavel LOIKO. 

This doctoral research was conducted within the framework of the ANR SPLENDID2 project. The thesis focused on the growth of single-crystalline thin films by liquid-phase epitaxy of Er³⁺-doped LiYF₄ and CaF₂ for laser waveguide development, coupled with comprehensive characterization of their morphological, microstructural, and spectroscopic properties. In parallel, an in-depth spectroscopic study was performed on Er³⁺-doped fluoride single crystals and sesquioxide transparent ceramics, with particular attention to materials exhibiting inhomogeneous spectral broadening, enabling broad and smooth emission bands around 2.8 µm. 

[1] L. Basyrova, P. Loiko, J.-L. Doualan, A. Benayad, A. Braud, B. Viana, and P. Camy, "Thermal lensing, heat loading and power scaling of mid-infrared Er:CaF₂ lasers," Opt. Express 30(5), 8092–8103 (2022). 

[2] L. Basyrova, P. Loiko, W. Jing, Y. Wang, H. Huang, M. Aguiló, F. Díaz, E. Dunina, A. Kornienko, B. Viana, U. Griebner, V. Petrov, X. Mateos, and P. Camy, "Spectroscopy and efficient laser operation around 2.8 μm of Er:(Lu,Sc)₂O₃ sesquioxide ceramics," J. Lumin. 240, 118373 (2021). '

[3] L. Basyrova, G. Brasse, P. Loiko, C. Grygiel, R. M. Solé, M. Aguiló, F. Díaz, X. Mateos, A. Benayad, J.-L. Doualan, and P. Camy, "Liquid Phase Epitaxy growth and structural characterization of highly doped Er³⁺:LiYF₄ thin films," Opt. Mater. 132, 112574 (2022). 

Liza BASYROVA is currently a Post-Doc at FEMTO-ST institute, Besançon, France.

PhD thesis (HAL archive)

Directeur: Alain BRAUD, co-directeur: Pavel LOIKO. 

The thesis establishes links between the structural properties of oxide and fluoride crystalline materials – both single crystals and transparent ceramics – and the spectroscopic and laser properties of thulium- and holmium-doped ions, which are critical for laser development. It also elucidates the physical mechanisms underlying unexpected laser behavior. This systematic investigation enables the identification of the most promising materials for broadly tunable and ultrashort-pulse lasers. The work primarily focuses on materials exhibiting strong inhomogeneous spectral broadening, leading to broad and structureless absorption and emission spectra. Several approaches to enhance this effect were explored, including rare-earth ion clustering, local structural disorder, compositional disorder in solid solutions, and phonon sidebands arising from electron–phonon interaction.

[1] K. Eremeev, P. Loiko, A. Benayad, P. Camy, and A. Braud, "Efficient continuous-wave Tm,Ho:CaF2 laser at 2.1 μm," Opt. Lett. 48(7), 1730–1733 (2023). 

[2] K. Eremeev, P. Loiko, R. Maksimov, V. Shitov, V. Osipov, D. Vakalov, V. Lapin, P. Camy, W. Chen, U. Griebner, V. Petrov, and A. Braud, "Highly efficient lasing and thermal properties of Tm:Y2O3 and Tm:(Y,Sc)2O3 ceramics," Opt. Lett. 48(15), 3901–3904 (2023). 

[3] K. Eremeev, P. Loiko, C. Zhao, Z.-L. Lin, X. Mateos, G. Z. Elabedine, P. Camy, A. Braud, U. Griebner, V. Petrov, G. Zhang, S. Li, Y. Hang, and W. Chen, "Growth, spectroscopy, and laser operation of Tm³⁺, Ho³⁺:GdScO₃ perovskite crystal," Opt. Express 32(8), 13527–13542 (2024). 

[4] K. Eremeev, P. Loiko, S. Balabanov, T. Evstropov, D. Permin, O. Postnikova, P. Camy, and A. Braud, "Spectroscopy of Thulium ions in solid-solution sesquioxide laser ceramics: inhomogeneous spectral line broadening, crystal-field engineering, and C₃ᵢ sites," Opt. Mater. 148, 114791 (2024). 

[5] X. Yu, K. Eremeev, Z. Pan, P. Loiko, H. Chu, H. Pan, A. Braud, P. Camy, and D. Li, "Polarized spectral properties and 2.3 μm laser performance of the Tm:YVO4 crystal," Opt. Express 32(10), 18055–18067 (2024).

Kirill EREMEEV is currently pursuing a Post-Doc position at CORIA laboratory, Université de Rouen, France.

PhD thesis (HAL archive) 

Directeur: Patrice CAMY, co-directeur: Pavel LOIKO. 

This doctoral research aimed to develop new functional inorganic materials – particularly rare-earth–heavily doped single crystals and single-crystalline thin films – and to demonstrate their potential for compact, efficient visible laser sources emitting in the orange, red, and deep-red. The study focused on: i) identifying the physical mechanisms limiting visible laser operation from Pr³⁺, Tb³⁺, Eu³⁺, and Sm³⁺ ions , known for their multicolor emission; (ii) evaluating oxide host materials, especially double tungstates and molybdates, for efficient visible lasing; and (iii) exploring promising but little-studied waveguide laser architectures compatible with integrated and fiber-laser technologies. The work notably reveals the anisotropy of electric- and magnetic-dipole transitions of Eu³⁺ ions in stoichiometric self-activated crystals. Efficient orange laser emission was achieved in a femtosecond-laser-inscribed fluoride waveguide. 

[1] A. Baillard, G. Brasse, P. Loiko, R. M. Solé, M. Aguiló, F. Díaz, X. Mateos, A. Benayad, A. Braud, and P. Camy, "Liquid Phase Epitaxy growth and spectroscopy of Tb³⁺, Gd³⁺:LiYF₄ crystalline layers," Opt. Mater. Express 13(8), 2355–2368 (2023). 

[2] A. Baillard, P. Loiko, C. Romero, V. Arroyo, J. R. V. de Aldana, M. Fromager, A. Benayad, A. Braud, P. Camy, and X. Mateos, "Orange surface waveguide laser in Pr:LiYF₄ produced by femtosecond laser writing," Opt. Lett. 48(23), 6212–6215 (2023). 

[3] A. Baillard, P. Loiko, D. Rytz, S. Schwung, M. Fromager, A. Braud, and P. Camy, "Red Sm:KGd(WO₄)₂ laser at 649 nm," Opt. Lett. 48(18), 4721–4724 (2023).

[4] A. Baillard, J. E. Bae, M. Ceballos, P. Loiko, R. M. Solé, M. Aguiló, F. Díaz, G. Brasse, X. Mateos, and P. Camy, "Deep-red planar waveguide laser operation of Eu³⁺:KY(WO₄)₂ layers," Opt. Express 33(3), 4926–4939 (2025). 

[5] A. Baillard, P.-A. Douissard, P. Loiko, L. Wollesen, T. Martin, E. Mathieu, E. Ziegler, G. Brasse, and P. Camy, “Terbium-doped gadolinium garnet thin films grown by Liquid Phase Epitaxy for scintillation detectors,” RSC Adv. 15(24), 18802-18813 (2025). 

Amandine BAILLARD is currently a Post-Doc at the Laval University, Canada.

Directeur: Alain BRAUD, co-directeur: Pavel LOIKO. 

This doctoral work is conducted within the ANR NOVELA project and aims to investigate the potential of novel oxide and fluoride materials in the form of single crystals, single-crystalline thin films, and optical fibers doped with rare-earth ions. The study focuses in particular on samarium (Sm³⁺, emitting in the orange and red), praseodymium (Pr³⁺, emitting in the green, orange, and red), and dysprosium (Dy³⁺, emitting in the yellow), with the goal of demonstrating their relevance for the development of compact, efficient, and high-power laser sources emitting directly in the visible range.

[1] J. Demaimay, E. Kifle, P. Loiko, F. Pau, G. Recoque, T. Georges, T. Rault, L. Bodin, F. Joulain, P. Camy, and A. Braud, "Efficient yellow Dy:ZBLAN fiber laser with high-brightness diode pumping at 450 nm," Opt. Lett. 49(15), 4174–4177 (2024). 

[2] J. Demaimay, J. E. Bae, P. Loiko, G. Brasse, F. Starecki, B. Guichardaz, A. Benayad, P. Camy, and A. Braud, “Diamond saw diced multi-color ridge Pr,Gd:LiYF₄ waveguide lasers,” Opt. Lett. 50(21), 6654-6657 (2025). 

[3] J. Demaimay, P. Loiko, E. Kifle, F. Pau, G. Recoque, A. Benayad, T. Georges, P. Camy, and A. Braud, "Diode-pumped orange Sm:LiYF₄ lasers emitting at 605 nm," Opt. Express 33(5), 9412–9422 (2025). 

[4] A. Sureshkumar, J. Demaimay, G. Perin, S. Hameed, M. Guendouz, H. Ollivier, Y. Dumeige, P. Loiko, G. Brasse, A. Braud, P. Camy, and S. Trebaol, "Yellow stimulated emission from Dy³⁺-doped silica glass microspheres," Opt. Express 33(7), 15802–15813 (2025).

Directeur: Alain BRAUD, co-directeur: Pavel LOIKO. 

This thesis builds on the ANR FLAMIR project by investigating low-phonon-energy infrared materials doped with active rare-earth ions for the development of next-generation mid-infrared lasers. The research activities encompass material synthesis and spectroscopic studies of three rare-earth ions (Ho³⁺, Dy³⁺, and Pr³⁺) doped into different host matrices selected for their infrared emission potential (2–4 µm), following a trend of decreasing maximum Raman-active phonon energy. The investigated hosts include sesquioxides (transparent ceramics), fluorides (crystals and glasses), and chalcogenides (glasses). 

[1] N. Q. H. Nguyen, P. Loiko, A. Benayad, E. Dunina, L. Fomicheva, A. Kornienko, P. Camy, and A. Braud, “Prospects of low-phonon energy Ho:MF₂ (M = Ca, Sr, Ba) crystals for 2-3 μm lasers,” Opt. Express 33(12), 24303-24320 (2025). 

[2] F. Delaunay, N. Q. H. Nguyen, N. Kerkad, R. Boulesteix, P. Loiko, A. Braud, P. Camy, V. Jubéra, and A. Maître, “Effect of fluorine addition on the microstructure and emis-sion properties of Ho:Y₂O₃ transparent ceramics,” Opt. Mater. 168, 117523 (2025).

Directeur: Pavel LOIKO, co-directeur: Alain BRAUD. 

This doctoral work, conducted within the ANR DUPLEX project, aims to develop innovative composite crystalline materials for mid-infrared laser applications. In particular, it focuses on diffusion-bonded (end-capped) crystals and transparent polycrystalline ceramics based on fluoride materials, a challenging yet highly promising family owing to their low phonon energy. It will further exploit emission in the 3-µm spectral range based on Erbium and Dysprosium ions.

Directeur: Ammar HIDEUR (Université de Rouen Normandie), co-directeur: Pavel LOIKO. 

This doctoral work, conducted within the I-DEMO LUMEN project, aims to develop novel all-fiber functional components (e.g., fiber combiners and splices) for fluoride fiber laser sources emitting in the visible range, in close collaboration with the company Le Verre Fluoré. The research involves a thorough investigation of ZrF4-based double-clad glass fibers, focusing on their splicing capability, resistance to crystallization under laser irradiation, and photodegradation behavior. The student regularly works between the Caen and Rouen sites to ensure effective progress.